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Treu L, Campanaro S, Kougias PG, Zhu X, Angelidaki I. Untangling the Effect of Fatty Acid Addition at Species Level Revealed Different Transcriptional Responses of the Biogas Microbial Community Members. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2016; 50:6079-90. [PMID: 27154312 DOI: 10.1021/acs.est.6b00296] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
In the present study, RNA-sequencing was used to elucidate the change of anaerobic digestion metatranscriptome after long chain fatty acids (oleate) exposure. To explore the general transcriptional behavior of the microbiome, the analysis was first performed on shotgun reads without considering a reference metagenome. As a second step, RNA reads were aligned on the genes encoded by the microbial community, revealing the expression of more than 51 000 different transcripts. The present study is the first research which was able to dissect the transcriptional behavior at a single species level by considering the 106 microbial genomes previously identified. The exploration of the metabolic pathways confirmed the importance of Syntrophomonas species in fatty acids degradation, and also highlighted the presence of protective mechanisms toward the long chain fatty acid effects in bacteria belonging to Clostridiales, Rykenellaceae, and in species of the genera Halothermothrix and Anaerobaculum. Additionally, an interesting transcriptional activation of the chemotaxis genes was evidenced in seven species belonging to Clostridia, Halothermothrix, and Tepidanaerobacter. Surprisingly, methanogens revealed a very versatile behavior different from each other, even among similar species of the Methanoculleus genus, while a strong increase of the expression level in Methanosarcina sp. was evidenced after oleate addition.
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Affiliation(s)
- Laura Treu
- Department of Environmental Engineering, Technical University of Denmark , 2800 Kgs. Lyngby, Denmark
- Department of Agronomy Food Natural Resources Animals and Environment (DAFNAE), University of Padova , Viale dell'Università 16, Legnaro, PD 35020, Italy
| | - Stefano Campanaro
- Department of Biology, University of Padova , Via U. Bassi 58/b, 35121, Padova Italy
| | - Panagiotis G Kougias
- Department of Environmental Engineering, Technical University of Denmark , 2800 Kgs. Lyngby, Denmark
| | - Xinyu Zhu
- Department of Environmental Engineering, Technical University of Denmark , 2800 Kgs. Lyngby, Denmark
| | - Irini Angelidaki
- Department of Environmental Engineering, Technical University of Denmark , 2800 Kgs. Lyngby, Denmark
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Complete Reconstitution of the Vancomycin-Intermediate Staphylococcus aureus Phenotype of Strain Mu50 in Vancomycin-Susceptible S. aureus. Antimicrob Agents Chemother 2016; 60:3730-42. [PMID: 27067329 PMCID: PMC4879404 DOI: 10.1128/aac.00420-16] [Citation(s) in RCA: 44] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2016] [Accepted: 04/01/2016] [Indexed: 12/23/2022] Open
Abstract
Complete reconstitution of the vancomycin-intermediate Staphylococcus aureus (VISA) phenotype of strain Mu50 was achieved by sequentially introducing mutations into six genes of vancomycin-susceptible S. aureus (VSSA) strain N315ΔIP. The six mutated genes were detected in VISA strain Mu50 but not in N315ΔIP. Introduction of the mutation Ser329Leu into vraS, encoding the sensor histidine kinase of the vraSR two-component regulatory (TCR) system, and another mutation, Glu146Lys, into msrR, belonging to the LytR-CpsA-Psr (LCP) family, increased the level of vancomycin resistance to that detected in heterogeneous vancomycin-intermediate S. aureus (hVISA) strain Mu3. Introduction of two more mutations, Asn197Ser into graR of the graSR TCR system and His481Tyr into rpoB, encoding the β subunit of RNA polymerase, converted the hVISA strain into a VISA strain with the same level of vancomycin resistance as Mu50. Surprisingly, however, the constructed quadruple mutant strain ΔIP4 did not have a thickened cell wall, a cardinal feature of the VISA phenotype. Subsequent study showed that cell wall thickening was an inducible phenotype in the mutant strain, whereas it was a constitutive one in Mu50. Finally, introduction of the Ala297Val mutation into fdh2, which encodes a putative formate dehydrogenase, or a 67-amino-acid sequence deletion into sle1 [sle1(Δ67aa)], encoding the hydrolase of N-acetylmuramyl-l-alanine amidase in the peptidoglycan, converted inducible cell wall thickening into constitutive cell wall thickening. sle1(Δ67aa) was found to cause a drastic decrease in autolysis activity. Thus, all six mutated genes required for acquisition of the VISA phenotype were directly or indirectly involved in the regulation of cell physiology. The VISA phenotype seemed to be achieved through multiple genetic events accompanying drastic changes in cell physiology.
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Kaushik KS, Ratnayeke N, Katira P, Gordon VD. The spatial profiles and metabolic capabilities of microbial populations impact the growth of antibiotic-resistant mutants. J R Soc Interface 2016; 12:rsif.2015.0018. [PMID: 25972434 DOI: 10.1098/rsif.2015.0018] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Antibiotic resistance adversely affects clinical and public health on a global scale. Using the opportunistic human pathogen Pseudomonas aeruginosa, we show that increasing the number density of bacteria, on agar containing aminoglycoside antibiotics, can non-monotonically impact the survival of antibiotic-resistant mutants. Notably, at high cell densities, mutant survival is inhibited. A wide range of bacterial species can inhibit antibiotic-resistant mutants. Inhibition results from the metabolic breakdown of amino acids, which results in alkaline by-products. The consequent increase in pH acts in conjunction with aminoglycosides to mediate inhibition. Our work raises the possibility that the manipulation of microbial population structure and nutrient environment in conjunction with existing antibiotics could provide therapeutic approaches to combat antibiotic resistance.
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Affiliation(s)
- Karishma S Kaushik
- Department of Molecular Biosciences, University of Texas, Austin, TX 78712, USA Center for Nonlinear Dynamics and Department of Physics, University of Texas, Austin, TX 78712, USA
| | - Nalin Ratnayeke
- Center for Nonlinear Dynamics and Department of Physics, University of Texas, Austin, TX 78712, USA
| | - Parag Katira
- Center for Nonlinear Dynamics and Department of Physics, University of Texas, Austin, TX 78712, USA
| | - Vernita D Gordon
- Center for Nonlinear Dynamics and Department of Physics, University of Texas, Austin, TX 78712, USA Institute of Cellular and Molecular Biology, University of Texas, Austin, TX 78712, USA
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Falcón R, Martínez A, Albert E, Madrid S, Oltra R, Giménez E, Soriano M, Vinuesa V, Gozalbo D, Gil ML, Navarro D. High vancomycin MICs within the susceptible range in Staphylococcus aureus bacteraemia isolates are associated with increased cell wall thickness and reduced intracellular killing by human phagocytes. Int J Antimicrob Agents 2016; 47:343-50. [PMID: 27056298 DOI: 10.1016/j.ijantimicag.2016.01.014] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2015] [Revised: 01/25/2016] [Accepted: 01/29/2016] [Indexed: 12/22/2022]
Abstract
Vancomycin minimum inhibitory concentrations (MICs) at the upper end of the susceptible range for Staphylococcus aureus have been associated with poor clinical outcomes of bloodstream infections. We tested the hypothesis that high vancomycin MICs in S. aureus bacteraemia isolates are associated with increased cell wall thickness and suboptimal bacterial internalisation or lysis by human phagocytes. In total, 95 isolates were evaluated. Original vancomycin MICs were determined by Etest. The susceptibility of S. aureus isolates to killing by phagocytes was assessed in a human whole blood assay. Internalisation of bacterial cells by phagocytes was investigated by flow cytometry. Cell wall thickness was evaluated by transmission electron microscopy. Genotypic analysis of S. aureus isolates was performed using a DNA microarray system. Vancomycin MICs were significantly higher (P=0.006) in isolates that were killed suboptimally (killing index <60%) compared with those killed efficiently (killing index >70%) and tended to correlate inversely (P=0.08) with the killing indices. Isolates in both killing groups were internalised by human neutrophils and monocytes with comparable efficiency. The cell wall was significantly thicker (P=0.03) in isolates in the low killing group. No genotypic differences were found between the isolates in both killing groups. In summary, high vancomycin MICs in S. aureus bacteraemia isolates were associated with increased cell wall thickness and reduced intracellular killing by phagocytes.
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Affiliation(s)
- Rocío Falcón
- Microbiology Service, Hospital Clínico Universitario de Valencia, Fundación INCLIVA, Valencia, Spain
| | - Alba Martínez
- Department of Microbiology, Faculty of Pharmacy, University of Valencia, Valencia, Spain
| | - Eliseo Albert
- Microbiology Service, Hospital Clínico Universitario de Valencia, Fundación INCLIVA, Valencia, Spain
| | - Silvia Madrid
- Microbiology Service, Hospital Clínico Universitario de Valencia, Fundación INCLIVA, Valencia, Spain
| | - Rosa Oltra
- Unit of Infectious Diseases, Hospital Clínico Universitario de Valencia, Fundación INCLIVA, Valencia, Spain
| | - Estela Giménez
- Microbiology Service, Hospital Clínico Universitario de Valencia, Fundación INCLIVA, Valencia, Spain
| | - Mario Soriano
- Centro de Investigación Príncipe Felipe, Valencia, Spain
| | - Víctor Vinuesa
- Microbiology Service, Hospital Clínico Universitario de Valencia, Fundación INCLIVA, Valencia, Spain
| | - Daniel Gozalbo
- Department of Microbiology, Faculty of Pharmacy, University of Valencia, Valencia, Spain
| | - María Luisa Gil
- Department of Microbiology, Faculty of Biological Sciences, University of Valencia, Valencia, Spain
| | - David Navarro
- Microbiology Service, Hospital Clínico Universitario de Valencia, Fundación INCLIVA, Valencia, Spain; Department of Microbiology, School of Medicine, University of Valencia, Valencia, Spain.
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The Quorum Sensing Inhibitor Hamamelitannin Increases Antibiotic Susceptibility of Staphylococcus aureus Biofilms by Affecting Peptidoglycan Biosynthesis and eDNA Release. Sci Rep 2016; 6:20321. [PMID: 26828772 PMCID: PMC4734334 DOI: 10.1038/srep20321] [Citation(s) in RCA: 116] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2015] [Accepted: 12/30/2015] [Indexed: 12/12/2022] Open
Abstract
Treatment of Staphylococcus aureus infections has become increasingly challenging due to the rapid emergence and dissemination of methicillin-resistant strains. In addition, S. aureus reside within biofilms at the site of infection. Few novel antibacterial agents have been developed in recent years and their bacteriostatic or bactericidal activity results in selective pressure, inevitably inducing antimicrobial resistance. Consequently, innovative antimicrobials with other modes of action are urgently needed. One alternative approach is targeting the bacterial quorum sensing (QS) system. Hamamelitannin (2′,5-di-O-galloyl-d-hamamelose; HAM) was previously suggested to block QS through the TraP QS system and was shown to increase S. aureus biofilm susceptibility towards vancomycin (VAN) although mechanistic insights are still lacking. In the present study we provide evidence that HAM specifically affects S. aureus biofilm susceptibility through the TraP receptor by affecting cell wall synthesis and extracellular DNA release of S. aureus. We further provide evidence that HAM can increase the susceptibility of S. aureus biofilms towards different classes of antibiotics in vitro. Finally, we show that HAM increases the susceptibility of S. aureus to antibiotic treatment in in vivo Caenorhabditis elegans and mouse mammary gland infection models.
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Chang HC, Huang YT, Chen CS, Chen YW, Huang YT, Su JC, Teng LJ, Shiau CW, Chiu HC. In vitro and in vivo activity of a novel sorafenib derivative SC5005 against MRSA. J Antimicrob Chemother 2015; 71:449-59. [PMID: 26553845 DOI: 10.1093/jac/dkv367] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2015] [Accepted: 10/08/2015] [Indexed: 02/06/2023] Open
Abstract
OBJECTIVES The emergence of MRSA strains resistant to most antibiotics is a serious threat to public health. Based on our discovery that the tyrosine kinase inhibitor sorafenib exhibits inhibitory activity against Staphylococcus species, the objective of this study is to exploit this unique antibacterial activity of sorafenib to develop novel antibacterial agents against MRSA. METHODS A sorafenib-based focused compound library was synthesized by substituting the pyridinyl and phenyl groups with different functional groups. The resulting sorafenib derivatives were screened for growth-suppressive activities against Staphylococcus aureus and Staphylococcus epidermidis following CLSI guidelines and for cytotoxicity towards human cells using MTT cell viability assays. Compounds with high selectivity for bacterial inhibition over cytotoxicity were further evaluated by time-kill assay and Caenorhabditis elegans and mice survival assays to evaluate their efficacy in vitro and in vivo. RESULTS The screening of sorafenib derivatives led to the identification of compound SC5005 as a lead compound with high potency in killing different clinical strains of MRSA with an MIC90 of 0.5 mg/L and with low cytotoxicity, as demonstrated by IC50-to-MIC ratios of up to 40. In addition, SC5005 showed a significant protective effect in MSSA- or MRSA-infected C. elegans. Intraperitoneal administration of SC5005 at 10 mg/kg significantly improved the survival of MRSA-infected C57BL/6 mice. CONCLUSIONS In light of its high potency in suppressing MRSA in both in vitro and in vivo models, SC5005 represents a potential lead agent for continued preclinical development as a therapeutic intervention against MRSA.
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Affiliation(s)
- Han-Chu Chang
- Department of Clinical Laboratory Sciences and Medical Biotechnology, National Taiwan University, Taipei, Taiwan
| | - Yu-Ting Huang
- Institute of Biopharmaceutical Sciences, National Yang-Ming University, Taipei, Taiwan
| | - Chang-Shi Chen
- Institute of Basic Medical Sciences, National Cheng Kung University, Tainan, Taiwan
| | - Yi-Wei Chen
- Institute of Basic Medical Sciences, National Cheng Kung University, Tainan, Taiwan
| | - Yu-Tsung Huang
- Department of Clinical Laboratory Sciences and Medical Biotechnology, National Taiwan University, Taipei, Taiwan
| | - Jung-Chen Su
- Department of Clinical Laboratory Sciences and Medical Biotechnology, National Taiwan University, Taipei, Taiwan
| | - Lee-Jeng Teng
- Department of Clinical Laboratory Sciences and Medical Biotechnology, National Taiwan University, Taipei, Taiwan
| | - Chung-Wai Shiau
- Institute of Biopharmaceutical Sciences, National Yang-Ming University, Taipei, Taiwan
| | - Hao-Chieh Chiu
- Department of Clinical Laboratory Sciences and Medical Biotechnology, National Taiwan University, Taipei, Taiwan
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Chakraborty SP, Mahapatra SK, Roy S. Biochemical characters and antibiotic susceptibility of Staphylococcus aureus isolates. Asian Pac J Trop Biomed 2015; 1:212-6. [PMID: 23569761 DOI: 10.1016/s2221-1691(11)60029-4] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2011] [Revised: 03/03/2011] [Accepted: 03/10/2011] [Indexed: 11/24/2022] Open
Abstract
OBJECTIVE To observe the biochemical characters and antibiotic susceptibility of isolated Staphylococcus aureus (S. auerus) strains against some conventional and traditional antibiotics. METHODS Thirty post operative pathogenic isolated S. aureus strains were used in this study. Bacterial culture was done in Mueller-Hinton broth at 37 °C. Characters of these strains were determined by traditional biochemical tests such as hydrolysis test of gelatin, urea, galactose, starch and protein, and fermentation of lactose and sucrose. Antibiotic susceptibility were carried out by minimum inhibitory concentration test, minium bactericidal concentration test, disc agar diffusion test and brain heart infusion oxacillin screening agar. RESULTS From this study, it was observed that 100% S. aureus isolates showed positive results in gelatin, urea and galactose hydrolysis test, 50% isolates were positive in starch hydrolysis test, 35% in protein hydrolysis test, 100% isolates in lactose fermenting test, but no isolate was positive in sucrose fermenting test. Antibiotic susceptibility testing suggested that 20% of isolates were resistant to kanamycin and 46.67% were resistant to oxacillin. CONCLUSIONS These findings show that all these isolates have gelatin, urea, galactose hydrolysis and lactose fermenting activity. 20% of these isolates were resistant to kanamycin and 46.67% were resistant to oxacillin.
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Affiliation(s)
- Subhankari Prasad Chakraborty
- Immunology and Microbiology Laboratory, Department of Human Physiology with Community Health, Vidyasagar University, Midnapore-721 102, West Bengal, India
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Maria-Neto S, de Almeida KC, Macedo MLR, Franco OL. Understanding bacterial resistance to antimicrobial peptides: From the surface to deep inside. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2015; 1848:3078-88. [PMID: 25724815 DOI: 10.1016/j.bbamem.2015.02.017] [Citation(s) in RCA: 116] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/11/2014] [Revised: 02/13/2015] [Accepted: 02/15/2015] [Indexed: 11/27/2022]
Abstract
Resistant bacterial infections are a major health problem in many parts of the world. The major commercial antibiotic classes often fail to combat common bacteria. Although antimicrobial peptides are able to control bacterial infections by interfering with microbial metabolism and physiological processes in several ways, a large number of cases of resistance to antibiotic peptide classes have also been reported. To gain a better understanding of the resistance process various technologies have been applied. Here we discuss multiple strategies by which bacteria could develop enhanced antimicrobial peptide resistance, focusing on sub-cellular regions from the surface to deep inside, evaluating bacterial membranes, cell walls and cytoplasmic metabolism. Moreover, some high-throughput methods for antimicrobial resistance detection and discrimination are also examined. This article is part of a Special Issue entitled: Bacterial Resistance to Antimicrobial Peptides.
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Affiliation(s)
- Simone Maria-Neto
- Laboratório de Purificação de Proteínas e suas Funções Biológicas, Centro de Ciências Biológicas e da Saúde, Universidade Federal de Mato Grosso do Sul, Cidade Universitária S/N - Caixa Postal 549, 79070-900, Campo Grande, MS, Brazil; Programa de Pós-Graduação em Saúde e Desenvolvimento na Região Centro-Oeste, Universidade Federal de Mato Grosso do Sul, Campo Grande, MS, Brazil
| | - Keyla Caroline de Almeida
- Centro de Análises Proteômicas e Bioquímicas, Pós-Graduação em Ciências Genômicas e Biotecnologia, Universidade Católica de Brasília, 70790-160 Brasília, DF, Brazil
| | - Maria Ligia Rodrigues Macedo
- Laboratório de Purificação de Proteínas e suas Funções Biológicas, Centro de Ciências Biológicas e da Saúde, Universidade Federal de Mato Grosso do Sul, Cidade Universitária S/N - Caixa Postal 549, 79070-900, Campo Grande, MS, Brazil
| | - Octávio Luiz Franco
- Centro de Análises Proteômicas e Bioquímicas, Pós-Graduação em Ciências Genômicas e Biotecnologia, Universidade Católica de Brasília, 70790-160 Brasília, DF, Brazil; S-Inova, Pós-Graduação em Biotecnologia, Universidade Católica Dom Bosco, 79117-900 Campo Grande, MS, Brazil.
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Hattangady DS, Singh AK, Muthaiyan A, Jayaswal RK, Gustafson JE, Ulanov AV, Li Z, Wilkinson BJ, Pfeltz RF. Genomic, Transcriptomic and Metabolomic Studies of Two Well-Characterized, Laboratory-Derived Vancomycin-Intermediate Staphylococcus aureus Strains Derived from the Same Parent Strain. Antibiotics (Basel) 2015; 4:76-112. [PMID: 27025616 PMCID: PMC4790321 DOI: 10.3390/antibiotics4010076] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2014] [Revised: 11/20/2014] [Accepted: 12/10/2014] [Indexed: 11/16/2022] Open
Abstract
Complete genome comparisons, transcriptomic and metabolomic studies were performed on two laboratory-selected, well-characterized vancomycin-intermediate Staphylococcus aureus (VISA) derived from the same parent MRSA that have changes in cell wall composition and decreased autolysis. A variety of mutations were found in the VISA, with more in strain 13136p(-)m⁺V20 (vancomycin MIC = 16 µg/mL) than strain 13136p(-)m⁺V5 (MIC = 8 µg/mL). Most of the mutations have not previously been associated with the VISA phenotype; some were associated with cell wall metabolism and many with stress responses, notably relating to DNA damage. The genomes and transcriptomes of the two VISA support the importance of gene expression regulation to the VISA phenotype. Similarities in overall transcriptomic and metabolomic data indicated that the VISA physiologic state includes elements of the stringent response, such as downregulation of protein and nucleotide synthesis, the pentose phosphate pathway and nutrient transport systems. Gene expression for secreted virulence determinants was generally downregulated, but was more variable for surface-associated virulence determinants, although capsule formation was clearly inhibited. The importance of activated stress response elements could be seen across all three analyses, as in the accumulation of osmoprotectant metabolites such as proline and glutamate. Concentrations of potential cell wall precursor amino acids and glucosamine were increased in the VISA strains. Polyamines were decreased in the VISA, which may facilitate the accrual of mutations. Overall, the studies confirm the wide variability in mutations and gene expression patterns that can lead to the VISA phenotype.
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Affiliation(s)
- Dipti S Hattangady
- School of Biological Sciences, Illinois State University, Normal, IL 61790, USA.
| | - Atul K Singh
- School of Biological Sciences, Illinois State University, Normal, IL 61790, USA.
| | - Arun Muthaiyan
- School of Biological Sciences, Illinois State University, Normal, IL 61790, USA.
| | | | - John E Gustafson
- Department of Biochemistry and Molecular Biology, Oklahoma State University, Stillwater, OK 74078, USA.
| | - Alexander V Ulanov
- Roy J. Carver Biotechnology Center, University of Illinois at Urbana-Champaign, Urbana, IL 61807, USA.
| | - Zhong Li
- Roy J. Carver Biotechnology Center, University of Illinois at Urbana-Champaign, Urbana, IL 61807, USA.
| | - Brian J Wilkinson
- School of Biological Sciences, Illinois State University, Normal, IL 61790, USA.
| | - Richard F Pfeltz
- BD Diagnostic Systems, Microbiology Research and Development, Sparks, MD 21152, USA.
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Shiba M, Yanai M, Maeda H, Shiono M. Fatal persistent methicillin-resistant Staphylococcus aureus bacteremia and vascular graft infections complicated with the formation of multiple abscesses despite aggressive medical therapy. SAGE Open Med Case Rep 2015; 3:2050313X15591314. [PMID: 27489691 PMCID: PMC4857327 DOI: 10.1177/2050313x15591314] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2015] [Accepted: 05/19/2015] [Indexed: 11/17/2022] Open
Abstract
A 40-year-old man underwent ascending aorta replacement for an acute type A aortic dissection. After the operations, methicillin-resistant Staphylococcus aureus was identified in sputum and blood cultures. Although anti-methicillin-resistant Staphylococcus aureus drugs were administered, most of the intermittent blood cultures remained positive. The focus of methicillin-resistant Staphylococcus aureus infection was not evident in the early stages, and no specific symptoms such as abscess or endocarditis were observed. However, abscesses in the brain, mediastinum and spleen were found 3 years after the operation. The minimum inhibitory concentration of vancomycin gradually increased from 1 to 4 µg/mL during the course of treatment. This case provides evidence for a potential role of combination therapy.
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Affiliation(s)
- Mikio Shiba
- Division of Cardiovascular, Respiratory and General Surgery, Department of Surgery, Nihon University School of Medicine, Tokyo, Japan; Department of Cardiovascular Medicine, National Cerebral and Cardiovascular Center, Osaka, Japan
| | - Mitsuru Yanai
- Division of General Medicine, Department of Internal Medicine, Nihon University School of Medicine, Tokyo, Japan
| | - Hideaki Maeda
- Division of Cardiovascular, Respiratory and General Surgery, Department of Surgery, Nihon University School of Medicine, Tokyo, Japan
| | - Motomi Shiono
- Division of Cardiovascular, Respiratory and General Surgery, Department of Surgery, Nihon University School of Medicine, Tokyo, Japan
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Kim SJ, Chang J, Singh M. Peptidoglycan architecture of Gram-positive bacteria by solid-state NMR. BIOCHIMICA ET BIOPHYSICA ACTA 2015; 1848:350-62. [PMID: 24915020 PMCID: PMC4258515 DOI: 10.1016/j.bbamem.2014.05.031] [Citation(s) in RCA: 96] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/31/2014] [Revised: 05/30/2014] [Accepted: 05/31/2014] [Indexed: 10/25/2022]
Abstract
Peptidoglycan is an essential component of cell wall in Gram-positive bacteria with unknown architecture. In this review, we summarize solid-state NMR approaches to address some of the unknowns in the Gram-positive bacteria peptidoglycan architecture: 1) peptidoglycan backbone conformation, 2) PG-lattice structure, 3) variations in the peptidoglycan architecture and composition, 4) the effects of peptidoglycan bridge-length on the peptidoglycan architecture in Fem mutants, 5) the orientation of glycan strands with respect to the membrane, and 6) the relationship between the peptidoglycan structure and the glycopeptide antibiotic mode of action. Solid-state NMR analyses of Staphylococcus aureus cell wall show that peptidoglycan chains are surprisingly ordered and densely packed. The peptidoglycan disaccharide backbone adopts 4-fold screw helical symmetry with the disaccharide unit periodicity of 40Å. Peptidoglycan lattice in the S. aureus cell wall is formed by cross-linked PG stems that have parallel orientations. The structural characterization of Fem-mutants of S. aureus with varying lengths of bridge structures suggests that the PG-bridge length is an important determining factor for the PG architecture.
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Affiliation(s)
- Sung Joon Kim
- Department of Chemistry and Biochemistry, Baylor University, Waco, TX 76706, USA.
| | - James Chang
- Department of Chemistry and Biochemistry, Baylor University, Waco, TX 76706, USA
| | - Manmilan Singh
- Department of Chemistry, Washington University, St. Louis, MO 63130, USA
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Zhu X, Liu C, Gao S, Lu Y, Chen Z, Sun Z. Vancomycin intermediate-resistant Staphylococcus aureus (VISA) isolated from a patient who never received vancomycin treatment. Int J Infect Dis 2014; 33:185-90. [PMID: 25543098 DOI: 10.1016/j.ijid.2014.12.038] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2014] [Revised: 12/13/2014] [Accepted: 12/20/2014] [Indexed: 10/24/2022] Open
Abstract
BACKGROUND With the abuse of antibiotics, the methicillin-resistant Staphylococcus aureus (MRSA) strain became prevalent. Furthermore, Staphylococcus aureus with a character of vancomycin intermediate-resistance (VISA) has been found globally since the first report in Japan. The main objectives of this study were to report a case of VISA isolated from a Chinese patient who had never undergone Vancomycin treatment, and to determine its molecular character. METHODS A total of 9 strains were recovered from a patient during the therapeutic process. Antimicrobial susceptibility testing was performed to determine their antibiotic susceptibility patterns. To detect the VISA strain's molecular epidemiological features, growth and morphological characters, we used multilocus sequence typing, autolysis assay and transmission electric microscope tests. Pulsed-field gel electrophoresis (PFGE) was performed to characterize the heterogeneities of all isolates. RESULTS One isolate was found to exhibit vancomycin intermediated-resistant with MIC of 8 μg/ml. It was ST239-T030-agr-1, had thickened cell wall, and displayed a slower growth rate and reduced susceptibility to Triton X-100-induced autolysis than other strains. All 9 strains exhibited the same PFGE pattern. CONCLUSION This is the first report of VISA found in central China from a patient who had never received vancomycin treatment.
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Affiliation(s)
- Xuhui Zhu
- Department of Clinical Laboratory, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Cailin Liu
- Department of Clinical Laboratory, the First Affiliated Hospital of Zhengzhou University, Zhengzhou, 450052, China
| | - Sui Gao
- Department of Clinical Laboratory, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Yanfang Lu
- Department of Clinical Laboratory, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Zhongju Chen
- Department of Clinical Laboratory, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China
| | - Ziyong Sun
- Department of Clinical Laboratory, Tongji Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, 430030, China.
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Hiramatsu K, Kayayama Y, Matsuo M, Aiba Y, Saito M, Hishinuma T, Iwamoto A. Vancomycin-intermediate resistance in Staphylococcus aureus. J Glob Antimicrob Resist 2014; 2:213-224. [DOI: 10.1016/j.jgar.2014.04.006] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2014] [Revised: 04/11/2014] [Accepted: 04/22/2014] [Indexed: 10/25/2022] Open
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Hiramatsu K, Katayama Y, Matsuo M, Sasaki T, Morimoto Y, Sekiguchi A, Baba T. Multi-drug-resistant Staphylococcus aureus and future chemotherapy. J Infect Chemother 2014; 20:593-601. [PMID: 25172776 DOI: 10.1016/j.jiac.2014.08.001] [Citation(s) in RCA: 129] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2014] [Revised: 07/31/2014] [Accepted: 08/01/2014] [Indexed: 11/17/2022]
Abstract
Staphylococcus (S.) aureus silently stays as our natural flora, and yet sometimes threatens our life as a tenacious pathogen. In addition to its ability to outwit our immune system, its multi-drug resistance phenotype makes it one of the most intractable pathogenic bacteria in the history of antibiotic chemotherapy. It conquered practically all the antibiotics that have been developed since 1940s. In 1961, the first MRSA was found among S. aureus clinical isolates. Then MRSA prevailed throughout the world as a multi-resistant hospital pathogen. In 1997, MRSA strain Mu50 with reduced susceptibility to vancomycin was isolated. Vancomycin-intermediate S. aureus (VISA), so named according to the CLSI criteria, was the product of adaptive mutation of S. aureus against vancomycin that had long been the last resort to MRSA infection. Here, we describe the genetic basis for the remarkable ability of S. aureus to acquire multi-antibiotic resistance, and propose a novel paradigm for future chemotherapy against the multi-resistant pathogens.
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Affiliation(s)
- K Hiramatsu
- Research Center for Infection Control Science, Juntendo University, 2-1-1 Hongo, Bunkyo-Ku, Tokyo, Japan.
| | - Y Katayama
- Research Center for Infection Control Science, Juntendo University, 2-1-1 Hongo, Bunkyo-Ku, Tokyo, Japan
| | - M Matsuo
- Research Center for Infection Control Science, Juntendo University, 2-1-1 Hongo, Bunkyo-Ku, Tokyo, Japan
| | - T Sasaki
- Research Center for Infection Control Science, Juntendo University, 2-1-1 Hongo, Bunkyo-Ku, Tokyo, Japan
| | - Y Morimoto
- Research Center for Infection Control Science, Juntendo University, 2-1-1 Hongo, Bunkyo-Ku, Tokyo, Japan
| | - A Sekiguchi
- Research Center for Infection Control Science, Juntendo University, 2-1-1 Hongo, Bunkyo-Ku, Tokyo, Japan
| | - T Baba
- Research Center for Infection Control Science, Juntendo University, 2-1-1 Hongo, Bunkyo-Ku, Tokyo, Japan
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The msaABCR operon regulates resistance in vancomycin-intermediate Staphylococcus aureus strains. Antimicrob Agents Chemother 2014; 58:6685-95. [PMID: 25155591 DOI: 10.1128/aac.03280-14] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Vancomycin-intermediate Staphylococcus aureus (VISA) strains present an increasingly difficult problem in terms of public health. However, the molecular mechanism for this resistance is not yet understood. In this study, we define the role of the msaABCR operon in vancomycin resistance in three clinical VISA strains, i.e., Mu50, HIP6297, and LIM2. Deletion of the msaABCR operon resulted in significant decreases in the vancomycin MIC (from 6.25 to 1.56 μg/ml) and significant reductions of cell wall thickness in strains Mu50 and HIP6297. Growth of the mutants in medium containing vancomycin at concentrations greater than 2 μg/ml resulted in decreases in the growth rate, compared with the wild-type strains. Mutation of the msaABCR operon also reduced the binding capacity for vancomycin. We conclude that the msaABCR operon contributes to resistance to vancomycin and cell wall synthesis in S. aureus.
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66
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Glycopeptide antibiotics: Back to the future. J Antibiot (Tokyo) 2014; 67:631-44. [DOI: 10.1038/ja.2014.111] [Citation(s) in RCA: 170] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2014] [Revised: 07/17/2014] [Accepted: 07/18/2014] [Indexed: 12/22/2022]
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Berscheid A, François P, Strittmatter A, Gottschalk G, Schrenzel J, Sass P, Bierbaum G. Generation of a vancomycin-intermediate Staphylococcus aureus (VISA) strain by two amino acid exchanges in VraS. J Antimicrob Chemother 2014; 69:3190-8. [PMID: 25103491 DOI: 10.1093/jac/dku297] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023] Open
Abstract
OBJECTIVES Staphylococcus aureus is a notorious bacterial pathogen and antibiotic-resistant isolates complicate current treatment strategies. We characterized S. aureus VC40, a laboratory mutant that shows full resistance to glycopeptides (vancomycin and teicoplanin MICs ≥32 mg/L) and daptomycin (MIC = 4 mg/L), to gain deeper insights into the underlying resistance mechanisms. METHODS Genomics and transcriptomics were performed to characterize changes that might contribute to development of resistance. The mutations in vraS were reconstituted into a closely related parental background. In addition, antimicrobial susceptibility testing, growth analyses, transmission electron microscopy, lysostaphin-induced lysis and autolysis assays were performed to characterize the phenotype of resistant strains. RESULTS Genome sequencing of strain VC40 revealed 79 mutations in 75 gene loci including genes encoding the histidine kinases VraS and WalK that control cell envelope-related processes. Transcriptomics indicated the increased expression of their respective regulons. Although not reaching the measured MIC for VC40, reconstitution of the L114S and D242G exchanges in VraS(VC40) into the susceptible parental background (S. aureus NCTC 8325) resulted in increased resistance to glycopeptides and daptomycin. The expression of VraS(VC40) led to increased transcription of the cell wall stress stimulon, a thickened cell wall, a decreased growth rate, reduced autolytic activity and increased resistance to lysostaphin-induced lysis in the generated mutant. CONCLUSIONS We show that a double mutation of a single gene locus, namely vraS, is sufficient to convert the vancomycin-susceptible strain S. aureus NCTC 8325 into a vancomycin-intermediate S. aureus.
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Affiliation(s)
- Anne Berscheid
- Institute of Medical Microbiology, Immunology and Parasitology (IMMIP), University of Bonn, Bonn, Germany
| | - Patrice François
- Genomic Research Laboratory, Infectious Diseases Service, Geneva University Hospitals and the University of Geneva, Geneva, Switzerland
| | - Axel Strittmatter
- Institute of Microbiology and Genetics, University of Göttingen, Göttingen, Germany
| | - Gerhard Gottschalk
- Institute of Microbiology and Genetics, University of Göttingen, Göttingen, Germany
| | - Jacques Schrenzel
- Genomic Research Laboratory, Infectious Diseases Service, Geneva University Hospitals and the University of Geneva, Geneva, Switzerland
| | - Peter Sass
- Institute for Pharmaceutical Biology, University of Düsseldorf, Düsseldorf, Germany
| | - Gabriele Bierbaum
- Institute of Medical Microbiology, Immunology and Parasitology (IMMIP), University of Bonn, Bonn, Germany
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Marchi E, Furi L, Arioli S, Morrissey I, Di Lorenzo V, Mora D, Giovannetti L, Oggioni MR, Viti C. Novel insight into antimicrobial resistance and sensitivity phenotypes associated to qac and norA genotypes in Staphylococcus aureus. Microbiol Res 2014; 170:184-94. [PMID: 25081379 DOI: 10.1016/j.micres.2014.07.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2014] [Revised: 07/04/2014] [Accepted: 07/06/2014] [Indexed: 10/25/2022]
Abstract
Staphylococcus aureus strains harboring QacA, QacB, QacC, QacG transporters and norA promoter up-regulating mutations were characterized by phenotype microarray (PM), standard methods for susceptibility testing, and ethidium bromide efflux assays, in order to increase knowledge on phenotypes associated to efflux pumps and their substrates. PM data and standard susceptibility testing lead to the identification of new potential efflux targets, such as guanidine hydrochloride or 8-hydroxyquinoline for QacA and QacC pumps, respectively. The identification of compounds to which the presence of efflux pumps induced increased susceptibility opens new perspectives for potential adjunct anti-resistance treatment (i.e. strains bearing QacB transporters showed increased susceptibility to thioridazine, amitriptyline and orphenadrine). Although the tested isolates were characterized by high degree of heterogeneity, a hallmark of clinical isolates, direct ethidium bromide efflux assays were effective in highlighting differences in efflux efficiency among strains. These data add to characterization of substrate specificity in the different classes of staphylococcal multidrug efflux systems conferring specific substrate profiles and efflux features to each of them.
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Affiliation(s)
- Emmanuela Marchi
- Dipartimento di Scienze delle Produzioni Agroalimentari e dell'Ambiente (DiSPAA), Università di Firenze, Piazzale delle Cascine, 18, Firenze, FI, Italy
| | - Leonardo Furi
- LAMMB, Dipartimento di Biotecnologie, Università di Siena, Policlinico Le Scotte (lotto 5, piano 1), Siena, SI, Italy
| | - Stefania Arioli
- Dipartimento di Scienze per gli Alimenti, la Nutrizione e l'Ambiente, via Mangiagalli, 25, Milano, MI, Italy
| | - Ian Morrissey
- Quotient Bioresearch, Newmarket Road, Fordham Cambridgeshire CB7 5WW, UK; IHMA Europe Sàrl, Route de la Corniche 9A, Epalinges, Switzerland
| | - Valeria Di Lorenzo
- Quotient Bioresearch, Newmarket Road, Fordham Cambridgeshire CB7 5WW, UK; IHMA Europe Sàrl, Route de la Corniche 9A, Epalinges, Switzerland
| | - Diego Mora
- Dipartimento di Scienze per gli Alimenti, la Nutrizione e l'Ambiente, via Mangiagalli, 25, Milano, MI, Italy
| | - Luciana Giovannetti
- Dipartimento di Scienze delle Produzioni Agroalimentari e dell'Ambiente (DiSPAA), Università di Firenze, Piazzale delle Cascine, 18, Firenze, FI, Italy
| | - Marco Rinaldo Oggioni
- LAMMB, Dipartimento di Biotecnologie, Università di Siena, Policlinico Le Scotte (lotto 5, piano 1), Siena, SI, Italy; Department of Genetics, University of Leicester, Adrian Building, University Road, Leicester, LE1 7RH, UK
| | - Carlo Viti
- Dipartimento di Scienze delle Produzioni Agroalimentari e dell'Ambiente (DiSPAA), Università di Firenze, Piazzale delle Cascine, 18, Firenze, FI, Italy.
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Exposure of Staphylococcus aureus to subinhibitory concentrations of β-lactam antibiotics induces heterogeneous vancomycin-intermediate Staphylococcus aureus. Antimicrob Agents Chemother 2014; 58:5306-14. [PMID: 24957836 DOI: 10.1128/aac.02574-14] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Glycopeptides are known to select for heterogeneous vancomycin-intermediate Staphylococcus aureus (h-VISA) from susceptible strains. In certain clinical situations, h-VISA strains have been isolated from patients without previous exposure to glycopeptides, such as cystic fibrosis patients, who frequently receive repeated treatments with beta-lactam antibiotics. Our objective was to determine whether prolonged exposure to beta-lactam antibiotics can induce h-VISA. We exposed 3 clinical vancomycin-susceptible methicillin-resistant Staphylococcus aureus (MRSA) strains to ceftazidime, ceftriaxone, imipenem, and vancomycin (as a control) at subinhibitory concentrations for 18 days in vitro. Population analyses showed progressive increases in vancomycin resistance; seven of the 12 derived strains obtained after induction were classified as h-VISA according to the following criteria: area under the curve (AUC) on day 18/AUC of Mu3 of ≥90% and/or growth on brain heart infusion (BHI) agar with 4 mg/liter vancomycin. The derived isolates had thickened cell walls proportional to the level of glycopeptide resistance. Genes known to be associated with glycopeptide resistance (vraSR, yvqF, SA1703, graRS, walKR, and rpoB) were PCR sequenced; no de novo mutations were observed upon beta-lactam exposure. To determine whether trfA, a gene encoding a glycopeptide resistance factor, was essential in the selection of h-VISA upon beta-lactam pressure, a trfA-knockout strain was generated by allelic replacement. Indeed, beta-lactam exposure of this mutated strain showed no capacity to induce vancomycin resistance. In conclusion, these results showed that beta-lactam antibiotics at subinhibitory concentrations can induce intermediate vancomycin resistance in vitro. This induction required an intact trfA locus. Our results suggest that prior use of beta-lactam antibiotics can compromise vancomycin efficacy in the treatment of MRSA infections.
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"Slow VISA," a novel phenotype of vancomycin resistance, found in vitro in heterogeneous vancomycin-intermediate Staphylococcus aureus strain Mu3. Antimicrob Agents Chemother 2014; 58:5024-35. [PMID: 24841271 DOI: 10.1128/aac.02470-13] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
Abstract
Heterogeneous vancomycin-intermediate Staphylococcus aureus (hVISA) clinical strain Mu3 spontaneously generates VISA strains at an extremely high frequency (≥1×10(-6)). The generated VISA strains usually grow more slowly than does the parent hVISA strain, but they form colonies on vancomycin-containing agar plates before 48 h of incubation. However, we noticed a curious group of VISA strains, designated "slow VISA" (sVISA), whose colonies appear only after 72 h of incubation. They have extremely prolonged doubling times but have vancomycin MICs of 8 to ∼24 mg/liter when determined after 72 to ∼144 h of incubation. We established strain Mu3-6R-P (6R-P), which has a vancomycin MIC of 16 mg/liter (at 72 h), as a representative sVISA strain. Its cell wall was thickened and autolytic activity was decreased compared to the respective qualities of the parent hVISA strain Mu3. Whole-genome sequencing of 6R-P revealed only one mutation, encoded by rpoB (R512P), which replaced the 512th arginine of the RNA polymerase β-subunit with proline. Its VISA phenotype was unstable, and the strain frequently reverted to hVISA with concomitant losses of pinpoint colony morphology and cell wall thickness and reduced autolytic activity. Sequencing of the rpoB genes of the phenotypic revertant strains revealed mutations affecting the 512th codon, where the proline of 6R-P was replaced with leucine, serine, or histidine. Slow VISA generated in the tissues of an infected patient serves as a temporary shelter for hVISA to survive vancomycin therapy. The sVISA strain spontaneously returns to hVISA when the threat of vancomycin is lifted. The rpoB(R512P) mutation may be regarded as a regulatory mutation that switches the reversible phenotype of sVISA on and off.
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Alexander EL, Gardete S, Bar HY, Wells MT, Tomasz A, Rhee KY. Intermediate-type vancomycin resistance (VISA) in genetically-distinct Staphylococcus aureus isolates is linked to specific, reversible metabolic alterations. PLoS One 2014; 9:e97137. [PMID: 24817125 PMCID: PMC4016254 DOI: 10.1371/journal.pone.0097137] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2013] [Accepted: 04/15/2014] [Indexed: 11/18/2022] Open
Abstract
Intermediate (VISA-type) vancomycin resistance in Staphylococcus aureus has been associated with a range of physiologic and genetic alterations. Previous work described the emergence of VISA-type resistance in two clonally-distinct series of isolates. In both series (the first belonging to MRSA clone ST8-USA300, and the second to ST5-USA100), resistance was conferred by a single mutation in yvqF (a negative regulator of the vraSR two-component system associated with vancomycin resistance). In the USA300 series, resistance was reversed by a secondary mutation in vraSR. In this study, we combined systems-level metabolomic profiling with statistical modeling techniques to discover specific, reversible metabolic alterations associated with the VISA phenotype.
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Affiliation(s)
- Elizabeth L. Alexander
- Division of Infectious Diseases, Department of Medicine, Weill Cornell Medical College, New York, New York, United States of America
- * E-mail: ;
| | - Susana Gardete
- Laboratory of Microbiology, The Rockefeller University, New York, New York, United States of America
| | - Haim Y. Bar
- Department of Statistics, University of Connecticut, Storrs, Connecticut, United States of America
| | - Martin T. Wells
- Department of Biological Statistics and Computational Biology and Department of Statistical Sciences, Cornell University, Ithaca, New York, United States of America
| | - Alexander Tomasz
- Laboratory of Microbiology, The Rockefeller University, New York, New York, United States of America
| | - Kyu Y. Rhee
- Division of Infectious Diseases, Department of Medicine, Weill Cornell Medical College, New York, New York, United States of America
- Department of Microbiology and Immunology, Weill Cornell Medical College, New York, New York, United States of America
- * E-mail: ;
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Alam MT, Petit RA, Crispell EK, Thornton TA, Conneely KN, Jiang Y, Satola SW, Read TD. Dissecting vancomycin-intermediate resistance in staphylococcus aureus using genome-wide association. Genome Biol Evol 2014; 6:1174-85. [PMID: 24787619 PMCID: PMC4040999 DOI: 10.1093/gbe/evu092] [Citation(s) in RCA: 93] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Vancomycin-intermediate Staphylococcus aureus (VISA) is currently defined as having minimal inhibitory concentration (MIC) of 4–8 µg/ml. VISA evolves through changes in multiple genetic loci with at least 16 candidate genes identified in clinical and in vitro-selected VISA strains. We report a whole-genome comparative analysis of 49 vancomycin-sensitive S. aureus and 26 VISA strains. Resistance to vancomycin was determined by broth microdilution, Etest, and population analysis profile-area under the curve (PAP-AUC). Genome-wide association studies (GWAS) of 55,977 single-nucleotide polymorphisms identified in one or more strains found one highly significant association (P = 8.78E-08) between a nonsynonymous mutation at codon 481 (H481) of the rpoB gene and increased vancomycin MIC. Additionally, we used a database of public S. aureus genome sequences to identify rare mutations in candidate genes associated with VISA. On the basis of these data, we proposed a preliminary model called ECM+RMCG for the VISA phenotype as a benchmark for future efforts. The model predicted VISA based on the presence of a rare mutation in a set of candidate genes (walKR, vraSR, graSR, and agrA) and/or three previously experimentally verified mutations (including the rpoB H481 locus) with an accuracy of 81% and a sensitivity of 73%. Further, the level of resistance measured by both Etest and PAP-AUC regressed positively with the number of mutations present in a strain. This study demonstrated 1) the power of GWAS for identifying common genetic variants associated with antibiotic resistance in bacteria and 2) that rare mutations in candidate gene, identified using large genomic data sets, can also be associated with resistance phenotypes.
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Affiliation(s)
- Md Tauqeer Alam
- Division of Infectious Diseases, Department of Medicine, Emory University School of Medicine
| | - Robert A Petit
- Division of Infectious Diseases, Department of Medicine, Emory University School of Medicine
| | - Emily K Crispell
- Division of Infectious Diseases, Department of Medicine, Emory University School of MedicineAtlanta Veterans Affairs Medical Center
| | | | - Karen N Conneely
- Department of Human Genetics, Emory University School of Medicine
| | - Yunxuan Jiang
- Department of Human Genetics, Emory University School of MedicineDepartment of Biostatistics and Bioinformatics, Emory University School of Public Health
| | - Sarah W Satola
- Division of Infectious Diseases, Department of Medicine, Emory University School of MedicineAtlanta Veterans Affairs Medical Center
| | - Timothy D Read
- Division of Infectious Diseases, Department of Medicine, Emory University School of MedicineDepartment of Human Genetics, Emory University School of Medicine
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The role of the Staphylococcal VraTSR regulatory system on vancomycin resistance and vanA operon expression in vancomycin-resistant Staphylococcus aureus. PLoS One 2014; 9:e85873. [PMID: 24454941 PMCID: PMC3893269 DOI: 10.1371/journal.pone.0085873] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2013] [Accepted: 12/09/2013] [Indexed: 11/19/2022] Open
Abstract
Vancomycin is often the preferred treatment for invasive methicillin-resistant Staphylococcus aureus (MRSA) infection. With the increase in incidence of MRSA infections, the use of vancomycin has increased and, as feared, isolates of vancomycin-resistant Staphylococcus aureus (VRSA) have emerged. VRSA isolates have acquired the entercoccal vanA operon contained on transposon (Tn) 1546 residing on a conjugal plasmid. VraTSR is a vancomycin and β-lactam-inducible three-component regulatory system encoded on the S. aureus chromosome that modulates the cell-wall stress response to cell-wall acting antibiotics. Mutation in vraTSR has shown to increase susceptibility to β-lactams and vancomycin in clinical VISA strains and in recombinant strain COLVA-200 which expresses a plasmid borne vanA operon. To date, the role of VraTSR in vanA operon expression in VRSA has not been demonstrated. In this study, the vraTSR operon was deleted from the first clinical VRSA strain (VRS1) by transduction with phage harvested from a USA300 vraTSR operon deletion strain. The absence of the vraTSR operon and presence of the vanA operon were confirmed in the transductant (VRS1Δvra) by PCR. Broth MIC determinations, demonstrated that the vancomycin MIC of VRS1Δvra (64 µg/ml) decreased by 16-fold compared with VRS1 (1024 µg/ml). The effect of the vraTSR operon deletion on expression of the van gene cluster (vanA, vanX and vanR) was examined by quantitative RT-PCR using relative quantification. A 2-5-fold decreased expression of the vanA operon genes occured in strain VRS1Δvra at stationary growth phase compared with the parent strain, VRS1. Both vancomycin resistance and vancomycin-induced expression of vanA and vanR were restored by complementation with a plasmid harboring the vraTSR operon. These findings demonstrate that expression in S. aureus of the horizontally acquired enterococcal vanA gene cluster is enhanced by the staphylococcal three-component cell wall stress regulatory system VraTSR, that is present in all S. aureus strains.
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Heizmann WR, Dupont H, Montravers P, Guirao X, Eckmann C, Bassetti M, García MS, Capparella MR, Simoneau D, Bodmann KF. Resistance mechanisms and epidemiology of multiresistant pathogens in Europe and efficacy of tigecycline in observational studies. J Antimicrob Chemother 2013; 68 Suppl 2:ii45-55. [PMID: 23772046 DOI: 10.1093/jac/dkt144] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
OBJECTIVES Antimicrobial drug resistance is a growing problem in Europe and, even with differences in epidemiology, it is of great concern. The treatment of complicated skin and soft-tissue infections (cSSTIs) and complicated intra-abdominal infections (cIAIs) is hindered further by pathogens that are resistant to methicillin, carbapenems, third-generation cephalosporins and glycopeptides. PATIENTS AND METHODS An analysis of the microbiological results from five European observational studies (July 2006 to October 2011) evaluating the efficacy of tigecycline (prescribed as monotherapy or in combination with other antibacterials) for the treatment of cSSTI and cIAI is presented. RESULTS In total, 213 cSSTI and 623 cIAI patients were included; 34.4% and 56.6%, respectively, were critically ill in intensive care units. At baseline, at least one pathogen was isolated in 167 (78.4%) cSSTI and 464 (74.5%) cIAI patients, and 32.9% and 49.1% of infections were polymicrobial. In cSSTI, Staphylococcus aureus and Escherichia coli (52.7% and 18.0%, respectively) were the most frequently isolated pathogens, whereas in cIAI most infections were due to E. coli (41.8%), Enterococcus faecium (40.1%) and Enterococcus faecalis (21.1%). Clinical response was observed in >80% of patients with E. coli in both cIAI and cSSTI. In cSSTI patients, the clinical response rate to S. aureus was 80.8%. For cIAI, 77.4% of E. faecium and 79.5% of E. faecalis patients responded to treatment. CONCLUSIONS Tigecycline when given alone or in combination with other antibacterials appeared to be efficacious against multiple pathogens, affirming its role in real-life clinical practice as a broad-spectrum antibacterial for the treatment of patients with cSSTI and cIAI, including the critically ill, across Europe.
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Onyango LA, Hugh Dunstan R, Roberts TK, Macdonald MM, Gottfries J. Phenotypic variants of staphylococci and their underlying population distributions following exposure to stress. PLoS One 2013; 8:e77614. [PMID: 24204894 PMCID: PMC3799968 DOI: 10.1371/journal.pone.0077614] [Citation(s) in RCA: 50] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2013] [Accepted: 09/04/2013] [Indexed: 11/18/2022] Open
Abstract
This study investigated whether alterations in environmental conditions would induce the formation of small colony variant phenotypes (SCV) with associated changes in cell morphology and ultra-structure in S. aureus, s. epidermidis, and S. lugdunensis. Wild-type clinical isolates were exposed to low temperature (4 °C), antibiotic stress (penicillin G and vancomycin; 0-10,000 µg mL(-1)), pH stress (pH 3-9) and osmotic challenge (NaCl concentrations of 0-20%). Changes in cell diameter, cell-wall thickness, and population distribution changes (n ≥ 300) were assessed via scanning and transmission electron microscopy (SEM and TEM), and compared to control populations. Our analyses found that prolonged exposure to all treatments resulted in the subsequent formation of SCV phenotypes. Observed SCVs manifested as minute colonies with reduced haemolysis and pigmentation (NaCl, pH and 4°C treatments), or complete lack thereof (antibiotic treatments). SEM comparison analyses revealed significantly smaller cell sizes for SCV populations except in S. aureus and S. epidermidis 10% NaCl, and S. epidermidis 4 °C (p<0.05). Shifts in population distribution patterns were also observed with distinct sub-populations of smaller cells appearing for S. epidermidis, and S. lugdunensis. TEM analyses revealed significantly thicker cell-walls in all treatments and species except S. lugdunensis exposed to 4 °C. These findings suggest that staphylococci adapted to environmental stresses by altering their cell size and wall thickness which could represent the formation of altered phenotypes which facilitate survival under harsh conditions. The phenotypic response was governed by the type of prevailing environmental stress regime leading to appropriate alterations in ultra-structure and size, suggesting downstream changes in gene expression, the proteome, and metabolome.
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Affiliation(s)
- Laura A. Onyango
- Environmental and Pathogenic Microbiology Laboratory, School of Environmental and Life Sciences, University of Newcastle, Newcastle, New South Wales, Australia
- * E-mail:
| | - R. Hugh Dunstan
- Environmental and Pathogenic Microbiology Laboratory, School of Environmental and Life Sciences, University of Newcastle, Newcastle, New South Wales, Australia
| | - Timothy K. Roberts
- Environmental and Pathogenic Microbiology Laboratory, School of Environmental and Life Sciences, University of Newcastle, Newcastle, New South Wales, Australia
| | - Margaret M. Macdonald
- Environmental and Pathogenic Microbiology Laboratory, School of Environmental and Life Sciences, University of Newcastle, Newcastle, New South Wales, Australia
| | - Johan Gottfries
- Department of Chemistry, Gothenburg University, Göteborg, Sweden
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Comprehensive identification of mutations responsible for heterogeneous vancomycin-intermediate Staphylococcus aureus (hVISA)-to-VISA conversion in laboratory-generated VISA strains derived from hVISA clinical strain Mu3. Antimicrob Agents Chemother 2013; 57:5843-53. [PMID: 24018261 DOI: 10.1128/aac.00425-13] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Heterogeneous vancomycin-intermediate Staphylococcus aureus (hVISA) spontaneously produces VISA cells within its cell population at a frequency of 10(-6) or greater. We established a total of 45 VISA mutant strains independently obtained from hVISA Mu3 and its related strains by one-step vancomycin selection. We then performed high-throughput whole-genome sequencing of the 45 strains and their parent strains to identify the genes involved in the hVISA-to-VISA phenotypic conversion. A comparative genome study showed that all the VISA strains tested carried a unique set of mutations. All of the 45 VISA strains carried 1 to 4 mutations possibly affecting the expression of a total of 48 genes. Among them, 32 VISA strains carried only one gene affected by a single mutation. As many as 20 genes in more than eight functional categories were affected in the 32 VISA strains, which explained the extremely high rates of the hVISA-to-VISA phenotypic conversion. Five genes, rpoB, rpoC, walK, pbp4, and pp2c, were previously reported as being involved in vancomycin resistance. Fifteen remaining genes were newly identified as associated with vancomycin resistance in this study. The gene most frequently affected (6 out of 32 strains) was cmk, which encodes cytidylate kinase, followed closely by rpoB (5 out of 32), encoding the β subunit of RNA polymerase. A mutation prevalence study also revealed a sizable number of cmk mutants among clinical VISA strains (7 out of 38 [18%]). Reduced cytidylate kinase activity in cmk mutant strains is proposed to contribute to the hVISA-to-VISA phenotype conversion by thickening the cell wall and reducing the cell growth rate.
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77
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MRSA detection in raw milk, some dairy products and hands of dairy workers in Egypt, a mini-survey. Food Control 2013. [DOI: 10.1016/j.foodcont.2013.02.017] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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78
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Daptomycin-nonsusceptible, vancomycin-intermediate, methicillin-resistant Staphylococcus aureus endocarditis. CANADIAN JOURNAL OF INFECTIOUS DISEASES & MEDICAL MICROBIOLOGY 2013; 23:e48-50. [PMID: 23730321 DOI: 10.1155/2012/138470] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
Due to the emergence of Staphylococcus aureus with reduced vancomycin susceptibility, newer antibiotics, including daptomycin, have been used to treat methicillin-resistant S aureus infections. Daptomycin is a cyclic lipopeptide that is approved to treat S aureus bacteremia and right-sided endocarditis, and reports of S aureus with reduced susceptibility to daptomycin are infrequent. To our knowledge, the present report describes the first Canadian case of daptomycin-nonsusceptible, vancomycin-intermediate S aureus infection.
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79
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Howden BP, Peleg AY, Stinear TP. The evolution of vancomycin intermediate Staphylococcus aureus (VISA) and heterogenous-VISA. INFECTION GENETICS AND EVOLUTION 2013; 21:575-82. [PMID: 23567819 DOI: 10.1016/j.meegid.2013.03.047] [Citation(s) in RCA: 97] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/04/2013] [Revised: 03/20/2013] [Accepted: 03/29/2013] [Indexed: 12/01/2022]
Abstract
Resistance to new antimicrobials is generally recognized in Staphylococcus aureus soon after they are released for clinical use. In the case of vancomycin, which was first released in the 1950s, resistance was not reported until the mid 1990s, with the description of vancomycin-intermediate S. aureus (VISA), and heterogenous-VISA (hVISA). Unraveling the complex genetic and cell wall structural changes conferring low-level vancomycin resistance in S. aureus has proved challenging. However the recent advances in high throughput whole-genome sequencing has played a key role in determining the breadth of bacterial chromosomal changes linked with resistance. Diverse mutations in a small number of staphylococcal regulatory genes, in particular walKR, graRS, vraSR and rpoB, have been associated with hVISA and VISA. Only a small number of these mutations have been experimentally proven to confer the resistance phenotype and some of these only partially contribute to resistance. It also appears that the evolution of VISA from VSSA is a step-wise process. Transcriptomics studies, and analysis of host pathogen interactions, indicate that the evolution of vancomycin-susceptible S. aureus to VISA is associated not only with antibiotic resistance, but with other changes likely to promote persistent infection. These include predicted alterations in central metabolism, altered expression of virulence associated factors, attenuated virulence in vivo, and alterations in susceptibility to host innate immune responses, together with reduced susceptibility to other antibiotics. In fact, current data suggests that hVISA and VISA represent a bacterial evolutionary state favoring persistence in the face of not only antibiotics, but also the host environment. The additional knowledge of staphylococcal biology that has been uncovered during the study of hVISA and VISA is significant. The present review will detail the current understanding of the evolutionary process in the generation of hVISA and VISA, and explore the diverse additional changes that occur in these strains.
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Affiliation(s)
- Benjamin P Howden
- Austin Centre for Infection Research (ACIR), Infectious Diseases Department, Austin Health, Heidelberg, Victoria, Australia; Microbiology Department, Austin Health, Heidelberg, Victoria, Australia; Department of Microbiology and Immunology, University of Melbourne, Victoria, Australia; Department of Microbiology, Monash University, Wellington Rd, Clayton, Victoria, Australia.
| | - Anton Y Peleg
- Department of Microbiology, Monash University, Wellington Rd, Clayton, Victoria, Australia; Division of Infectious Diseases, Beth Israel Deaconess Medical Center, Boston, MA, United States; Department of Infectious Diseases, The Alfred Hospital, Melbourne, Australia
| | - Timothy P Stinear
- Department of Microbiology and Immunology, University of Melbourne, Victoria, Australia; Department of Microbiology, Monash University, Wellington Rd, Clayton, Victoria, Australia
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80
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Jansen A, Szekat C, Schröder W, Wolz C, Goerke C, Lee JC, Türck M, Bierbaum G. Production of capsular polysaccharide does not influence Staphylococcus aureus vancomycin susceptibility. BMC Microbiol 2013; 13:65. [PMID: 23522028 PMCID: PMC3617075 DOI: 10.1186/1471-2180-13-65] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2013] [Accepted: 03/04/2013] [Indexed: 01/12/2023] Open
Abstract
Background Diverse mechanisms (increased cell wall thickness, low cross linking, decreased autolysis, etc.) have been reported for Staphylococcus aureus strains with intermediate vancomycin susceptibility (VISA). This study was conducted to identify common mechanisms responsible for decreased vancomycin susceptibility in a VISA strain pair. Results Transcriptional profiling of the clinical heterogeneous VISA isolate SA137/93A and its spontaneous homogeneous mutant strain SA137/93G pointed to an increased capsule production in the strain pair compared to a susceptible control. Furthermore, transcript quantification of the gene cap5E, which is essential for capsule biosynthesis, revealed elevated levels in the VISA strains SA137/93A, SA137/93G and Mu50 in comparison with susceptible strains Reynolds, Newman and SA1450/94. The increased expression was observed in bacteria from exponential as well as stationary growth phase. However, suppression of type 5 capsule formation by expression of antisense RNA did not increase vancomycin susceptibility in the VISA strain SA137/93G. Likewise, construction of inducible mutants of S. aureus Newman or repair of capsule biosynthesis of S. aureus HG001 and S. aureus 1450/94 did not influence resistance to vancomycin. Furthermore, purified type 5 polysaccharide did not protect indicator strains from the action of vancomycin. Conclusions The VISA strain tested in this study displayed an increased production of type 5 capsular polysaccharide. However, the production of capsule material did not protect strain SA137/93G and three vancomycin sensitive strains in the presence of vancomycin and thus is not part of the resistance mechanism; however it may represent a by-product of VISA life style that is often characterized by a high sigma factor B activity.
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Affiliation(s)
- Andrea Jansen
- Institut für Medizinische Mikrobiologie, Immunologie und Parasitologie, Universitätsklinikum Bonn, Sigmund-Freud-Str. 25, D-53105, Bonn, Germany
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81
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Rifaximin in the treatment of irritable bowel syndrome: is there a high risk for development of antimicrobial resistance? J Clin Gastroenterol 2013; 47:205-11. [PMID: 23340064 DOI: 10.1097/mcg.0b013e31827559a3] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
Abstract
Irritable bowel syndrome (IBS), a chronic, nonfatal illness is commonly encountered in clinical practice; however, treatment options are limited and often ineffectual. Despite this, there is increasing evidence that bacterial overgrowth in the bowel (dysbiosis) may be an etiological factor in IBS. This has lead to studies in which the antibiotic agent rifaximin has been used to reduce the microbial burden in the bowel, to some extent alleviating the symptoms of IBS. Rifaximin is a member of the rifamycin class of antibiotics, which when administered orally has the distinctions of being gut specific coupled with poor systemic absorption, characteristics that are suggested to limit the development of bacterial resistance. The rifamycins are currently used to treat serious human diseases including tuberculosis, meningococcal disease, methicillin-resistant Staphylococcus aureus and Clostridium difficile infections. The use of rifamycins in the treatment of these diseases is associated with the development of antibiotic resistance over time. When considering the importance of the rifamycins in the treatment of serious human diseases, the large number of patients affected by IBS, and the lack of scientific evidence available on the development of antibiotic resistance to rifaximin over the long-term when used in the gut, it is advisable that the use of rifaximin as a therapy for IBS should be limited to single, acute, short-term treatment.
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82
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Hyo Y, Yamada S, Fukutsuji K, Harada T. Thickening of the cell wall in macrolide-resistant Staphylococcus aureus. Med Mol Morphol 2013; 46:217-24. [PMID: 23408211 DOI: 10.1007/s00795-013-0027-y] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2012] [Accepted: 11/21/2012] [Indexed: 10/27/2022]
Abstract
Macrolides are widely used at low dosage for long-term therapy of chronic sinusitis. Twenty clinical macrolide-resistant Staphylococcus aureus strains were morphologically compared with 10 clinical macrolide-sensitive strains. PCR amplification was performed to determine the presence of four known macrolide resistance genes. Transmission electron microscopy revealed significantly thicker cell walls in clinical macrolide-resistant strains. Even though the ultrastructural characteristics were shared by all macrolide-resistant strains, they were not associated with the presence or absence of the known macrolide-resistance genes. We also demonstrated that macrolide-resistant mutant strains derived in vitro from a macrolide-sensitive parent strain had thickened cell walls and did not harbor the known macrolide-resistance genes. These results, therefore, revealed that macrolide-resistant S. aureus strains have thickened cell walls as a common ultrastructural characteristic and that cell wall thickening is likely mediated by an unknown gene which is unrelated to any known macrolide resistance gene.
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Affiliation(s)
- Yukiyoshi Hyo
- Department of Otolaryngology, Kawasaki Medical School, 577 Matsusima, Kurasiki, Okayama, 701-0192, Japan,
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83
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Synthesis and evaluation of antibacterial activity of 7-alkyloxy-4,5-dihydro-imidazo[1,2-a]quinoline derivatives. Eur J Med Chem 2013; 60:451-5. [DOI: 10.1016/j.ejmech.2012.12.034] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2012] [Revised: 12/11/2012] [Accepted: 12/17/2012] [Indexed: 11/19/2022]
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84
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Ultrastructural cell wall characteristics of clinical gentamycin-resistant Staphylococcus aureus isolates. Med Mol Morphol 2013; 46:70-6. [PMID: 23338781 DOI: 10.1007/s00795-013-0009-0] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2012] [Accepted: 03/26/2012] [Indexed: 10/27/2022]
Abstract
The frequent use of gentamycin (GM) ointment for the treatment of skin infections has led to an increase in the number of GM-resistant clinical isolates of Staphylococcus aureus. We examined the ultrastructural characteristics of 14 clinical strains of S. aureus by transmission electron microscopy. Seven of these isolates were GM-resistant, and seven isolates were GM-sensitive. We found that the cell wall of GM-resistant strains (32.24 ± 5.99 nm) was significantly thicker than that of GM-sensitive strains (19.02 ± 2.72 nm). We genetically characterized these isolates by polymerase chain reaction, targeting the genes for three aminoglycoside-modifying enzymes, aac(6')-aph(2''), aph(3')-III, and ant(4')-I. All GM-resistant strains tested carried the gene encoding aac(6')-aph(2''). However, we were unable to establish a link between a specific gene and cell wall thickening, because one GM-resistant strain was also positive for aph(3')-III. We also demonstrated that a GM-resistant mutant strain, derived in vitro from a GM-sensitive S. aureus parent strain (209P), also exhibited a thickened cell wall. These results strongly suggest that a thickened cell wall is a common ultrastructural characteristic of GM-resistant S. aureus clinical strains.
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85
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Chakraborty SP, Sahu SK, Pramanik P, Roy S. In vitro antimicrobial activity of nanoconjugated vancomycin against drug resistant Staphylococcus aureus. Int J Pharm 2012; 436:659-76. [PMID: 22841851 DOI: 10.1016/j.ijpharm.2012.07.033] [Citation(s) in RCA: 70] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2012] [Revised: 07/17/2012] [Accepted: 07/19/2012] [Indexed: 11/19/2022]
Abstract
The mounting problem of antibiotic resistance of Staphylococcus aureus has prompted renewed efforts toward the discovery of novel antimicrobial agents. The present study was aimed to evaluate the in vitro antimicrobial activity of nanoconjugated vancomycin against vancomycin sensitive and resistant S. aureus strains. Folic acid tagged chitosan nanoparticles are used as Trojan horse to deliver vancomycin into bacterial cells. In vitro antimicrobial activity of nanoconjugated vancomycin against VSSA and VRSA strains was determined by minimum inhibitory concentration, minimum bactericidal concentration, tolerance and disc agar diffusion test. Cell viability and biofilm formation was assessed as indicators of pathogenicity. To establish the possible antimicrobial mechanism of nanoconjugated vancomycin, the cell wall thickness was studied by TEM study. The result of the present study reveals that nano-sized vehicles enhance the transport of vancomycin across epithelial surfaces, and exhibits its efficient drug-action which has been understood from studies of MIC, MBC, DAD of chitosan derivative nanoparticle loaded with vancomycin. Tolerance values distinctly showed that vancomycin loaded into nano-conjugate is very effective and has strong bactericidal effect on VRSA. These findings strongly enhanced our understanding of the molecular mechanism of nanoconjugated vancomycin and provide additional rationale for application of antimicrobial therapeutic approaches for treatment of staphylococcal pathogenesis.
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Affiliation(s)
- Subhankari Prasad Chakraborty
- Immunology and Microbiology Laboratory, Department of Human Physiology with Community Health, Vidyasagar University, Midnapore 721102, West Bengal, India
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86
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Rogers TE, Ataide SF, Dare K, Katz A, Seveau S, Roy H, Ibba M. A pseudo-tRNA modulates antibiotic resistance in Bacillus cereus. PLoS One 2012; 7:e41248. [PMID: 22815980 PMCID: PMC3399842 DOI: 10.1371/journal.pone.0041248] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2012] [Accepted: 06/19/2012] [Indexed: 01/18/2023] Open
Abstract
Bacterial genomic islands are often flanked by tRNA genes, which act as sites for the integration of foreign DNA into the host chromosome. For example, Bacillus cereus ATCC14579 contains a pathogenicity island flanked by a predicted pseudo-tRNA, tRNAOther, which does not function in translation. Deletion of tRNAOther led to significant changes in cell wall morphology and antibiotic resistance and was accompanied by changes in the expression of numerous genes involved in oxidative stress responses, several of which contain significant complementarities to sequences surrounding tRNAOther. This suggested that tRNAOther might be expressed as part of a larger RNA, and RACE analysis subsequently confirmed the existence of several RNA species that significantly extend both the 3′ and 5′-ends of tRNAOther. tRNAOther expression levels were found to be responsive to changes in extracellular iron concentration, consistent with the presence of three putative ferric uptake regulator (Fur) binding sites in the 5′ leader region of one of these larger RNAs. Taken together with previous data, this study now suggests that tRNAOther may function by providing a tRNA-like structural element within a larger regulatory RNA. These findings illustrate that while integration of genomic islands often leaves tRNA genes intact and functional, in other instances inactivation may generate tRNA-like elements that are then recruited to other functions in the cell.
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Affiliation(s)
- Theresa E. Rogers
- Department of Microbiology, Ohio State University, Columbus, Ohio, United States of America
| | - Sandro F. Ataide
- Department of Microbiology, Ohio State University, Columbus, Ohio, United States of America
| | - Kiley Dare
- Department of Microbiology, Ohio State University, Columbus, Ohio, United States of America
| | - Assaf Katz
- Department of Microbiology, Ohio State University, Columbus, Ohio, United States of America
| | - Stephanie Seveau
- Department of Microbiology, Ohio State University, Columbus, Ohio, United States of America
| | - Hervé Roy
- Department of Microbiology, Ohio State University, Columbus, Ohio, United States of America
- Burnett School of Biomedical Sciences, University of Central Florida, Orlando, Florida, United States of America
| | - Michael Ibba
- Department of Microbiology, Ohio State University, Columbus, Ohio, United States of America
- Ohio State Biochemistry Program, Ohio State University, Columbus, Ohio, United States of America
- Center for RNA Biology, Ohio State University, Columbus, Ohio, United States of America
- * E-mail:
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87
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Chiu HC, Lee SL, Kapuriya N, Wang D, Chen YR, Yu SL, Kulp SK, Teng LJ, Chen CS. Development of novel antibacterial agents against methicillin-resistant Staphylococcus aureus. Bioorg Med Chem 2012; 20:4653-60. [PMID: 22750009 DOI: 10.1016/j.bmc.2012.06.018] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2012] [Revised: 06/01/2012] [Accepted: 06/08/2012] [Indexed: 02/06/2023]
Abstract
Methicillin-resistant Staphylococcus aureus (MRSA) poses a serious threat to public health because of its resistance to multiple antibiotics most commonly used to treat infection. In this study, we report the unique ability of the cyclooxygenase-2 (COX-2) inhibitor celecoxib to kill Staphylococcus aureus and MRSA with modest potency. We hypothesize that the anti-Staphylococcus activity of celecoxib could be pharmacologically exploited to develop novel anti-MRSA agents with a distinct mechanism. Examination of an in-house, celecoxib-based focused compound library in conjunction with structural modifications led to the identification of compound 46 as the lead agent with high antibacterial potency against a panel of Staphylococcus pathogens and different strains of MRSA. Moreover, this killing effect is bacteria-specific, as human cancer cells are resistant to 46. In addition, a single intraperitoneal administration of compound 46 at 30 mg/kg improved the survival of MRSA-infected C57BL/6 mice. In light of its high potency in eradicating MRSA in vitro and its in vivo activity, compound 46 and its analogues warrant continued preclinical development as a potential therapeutic intervention against MRSA.
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Affiliation(s)
- Hao-Chieh Chiu
- Department of Clinical Laboratory Sciences and Medical Biotechnology, National Taiwan University College of Medicine, Taipei 100, Taiwan
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88
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Vancomycin tolerance in methicillin-resistant Staphylococcus aureus: influence of vancomycin, daptomycin, and telavancin on differential resistance gene expression. Antimicrob Agents Chemother 2012; 56:4422-7. [PMID: 22687502 DOI: 10.1128/aac.00676-12] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023] Open
Abstract
Methicillin-resistant Staphylococcus aureus (MRSA) isolates that are susceptible to vancomycin but are tolerant to its killing effect may present a potential challenge for effective treatment. This study compared the microbiologic characteristics of clinical vancomycin-tolerant (VT-MRSA) and vancomycin-susceptible (VS-MRSA) strains using phenotypic and gene regulation studies. MRSA isolates collected from vancomycin-treated patients with bacteremia over a 5-year period were analyzed for vancomycin, daptomycin, and telavancin susceptibility, as well as accessory gene regulator (agr) group and function. Vancomycin tolerance was defined by a minimum bactericidal concentration (MBC)/minimum inhibitor concentration (MIC) ratio of ≥32 mg/liter. VT-MRSA isolates were compared to VS-MRSA isolates for differences in antimicrobial susceptibility, time-kill activity, and gene expression of key cell envelope response genes vraSR, dltA, and mprF. All 115 isolates evaluated were susceptible to vancomycin, daptomycin, and telavancin. Seven isolates (6%) were VT-MRSA. agr group II was more prevalent in isolates with vancomycin MBC/MIC ratios of ≥8. In time-kill analyses, VT-MRSA had reduced vancomycin killing, but daptomycin and telavancin activities were maintained. Significantly greater gene expression was observed in VT-MRSA after 72 h of subinhibitory antibiotic exposures. Vancomycin most notably increased vraSR expression (P = 0.002 versus VS-MRSA strains). Daptomycin and telavancin increased expression of all genes studied, most significantly mprF expression (P < 0.001). Longer durations of antibiotic exposure (72 h versus 24 h) resulted in substantial increases in gene expression in VT-MRSA. Although the clinical impact of VT-MRSA is not fully recognized, these data suggest that VT-MRSA strains, while still susceptible, have altered gene regulation to adapt to the antimicrobial effects of glyco- and lipopeptides that may emerge during prolonged durations of exposure.
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89
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Cameron DR, Ward DV, Kostoulias X, Howden BP, Moellering RC, Eliopoulos GM, Peleg AY. Serine/threonine phosphatase Stp1 contributes to reduced susceptibility to vancomycin and virulence in Staphylococcus aureus. J Infect Dis 2012; 205:1677-87. [PMID: 22492855 PMCID: PMC3415852 DOI: 10.1093/infdis/jis252] [Citation(s) in RCA: 79] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2011] [Accepted: 12/05/2011] [Indexed: 01/28/2023] Open
Abstract
The genetic mechanisms that contribute to reduced susceptibility to vancomycin in Staphylococcus aureus are complex and heterogeneous. In addition, debate is emerging as to the true effect of reduced susceptibility to vancomycin on staphylococcal virulence. To investigate this, comparative genomics was performed on a collection of vancomycin-exposed isogenic S. aureus pairs (14 strains in total). Previously described mutations were observed in genes such as vraG, agrA, yvqF, and rpoB; however, a new mechanism was identified involving a serine/threonine phosphatase, Stp1. After constructing an stp1 deletion mutant, we showed that stp1 is important in vancomycin susceptibility and cell wall biosynthesis. Gene expression studies showed that stp1 also regulates virulence genes, including a hemolysin, superantigen-like protein, and phenol-soluble modulin, and that the deletion mutant is attenuated in virulence in vivo. Stp1 provides a new link between vancomycin susceptibility and virulence in S. aureus.
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Affiliation(s)
- David R. Cameron
- Department of Microbiology, Monash University, Melbourne, Australia
| | | | - Xenia Kostoulias
- Department of Microbiology, Monash University, Melbourne, Australia
| | - Benjamin P. Howden
- Department of Microbiology, Monash University, Melbourne, Australia
- Austin Centre for Infection Research, Department of Infectious Diseases
- Department of Microbiology, Austin Hospital
- Department of Microbiology and Immunology, University of Melbourne, Melbourne, Australia
| | - Robert C. Moellering
- Division of Infectious Diseases, Beth Israel Deaconess Medical Center
- Harvard Medical School, Boston, Massachusetts
| | - George M. Eliopoulos
- Division of Infectious Diseases, Beth Israel Deaconess Medical Center
- Harvard Medical School, Boston, Massachusetts
| | - Anton Y. Peleg
- Department of Microbiology, Monash University, Melbourne, Australia
- Division of Infectious Diseases, Beth Israel Deaconess Medical Center
- Department of Infectious Diseases, The Alfred Hospital, Melbourne, Australia
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90
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Coordinated phenotype switching with large-scale chromosome flip-flop inversion observed in bacteria. Proc Natl Acad Sci U S A 2012; 109:E1647-56. [PMID: 22645353 DOI: 10.1073/pnas.1204307109] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Genome inversions are ubiquitous in organisms ranging from prokaryotes to eukaryotes. Typical examples can be identified by comparing the genomes of two or more closely related organisms, where genome inversion footprints are clearly visible. Although the evolutionary implications of this phenomenon are huge, little is known about the function and biological meaning of this process. Here, we report our findings on a bacterium that generates a reversible, large-scale inversion of its chromosome (about half of its total genome) at high frequencies of up to once every four generations. This inversion switches on or off bacterial phenotypes, including colony morphology, antibiotic susceptibility, hemolytic activity, and expression of dozens of genes. Quantitative measurements and mathematical analyses indicate that this reversible switching is stochastic but self-organized so as to maintain two forms of stable cell populations (i.e., small colony variant, normal colony variant) as a bet-hedging strategy. Thus, this heritable and reversible genome fluctuation seems to govern the bacterial life cycle; it has a profound impact on the course and outcomes of bacterial infections.
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91
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Relationship between vancomycin-resistant Staphylococcus aureus, vancomycin-intermediate S. aureus, high vancomycin MIC, and outcome in serious S. aureus infections. J Clin Microbiol 2012; 50:2548-52. [PMID: 22593595 DOI: 10.1128/jcm.00775-12] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023] Open
Abstract
Vancomycin has been used successfully for over 50 years for the treatment of Staphylococcus aureus infections, particularly those involving methicillin-resistant S. aureus. It has proven remarkably reliable, but its efficacy is now being questioned with the emergence of strains of S. aureus that display heteroresistance, intermediate resistance, and, occasionally, complete vancomycin resistance. More recently, an association has been established between poor outcome and infections with strains of S. aureus with an elevated vancomycin MIC within the susceptible range. This minireview summarizes the definitions, mechanisms, clinical impact, and laboratory identification of reduced vancomycin susceptibility in S. aureus and discusses practical issues for the diagnostic laboratory in testing and interpreting vancomycin susceptibility for S. aureus infections.
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92
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Kawada-Matsuo M, Komatsuzawa H. Factors affecting susceptibility of Staphylococcus aureus to antibacterial agents. J Oral Biosci 2012. [DOI: 10.1016/j.job.2012.04.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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93
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Zhou X, Dai YY, Ma XL. Be alert to the alterations in the biological characteristics in heterogeneous vancomycin-intermediate Staphylococcus aureus. Indian J Med Microbiol 2012; 30:215-7. [DOI: 10.4103/0255-0857.96696] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
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94
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Deciphering the magainin resistance process of Escherichia coli strains in light of the cytosolic proteome. Antimicrob Agents Chemother 2012; 56:1714-24. [PMID: 22290970 DOI: 10.1128/aac.05558-11] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Antimicrobial peptides (AMPs) are effective antibiotic agents commonly found in plants, animals, and microorganisms, and they have been suggested as the future of antimicrobial chemotherapies. It is vital to understand the molecular details that define the mechanism of action of resistance to AMPs for a rational planning of the next antibiotic generation and also to shed some light on the complex AMP mechanism of action. Here, the antibiotic resistance of Escherichia coli ATCC 8739 to magainin I was evaluated in the cytosolic subproteome. Magainin-resistant strains were selected after 10 subsequent spreads at subinhibitory concentrations of magainin I (37.5 mg · liter⁻¹), and their cytosolic proteomes were further compared to those of magainin-susceptible strains through two-dimensional electrophoresis analysis. As a result, 41 differentially expressed proteins were detected by in silico analysis and further identified by tandem mass spectrometry de novo sequencing. Functional categorization indicated an intense metabolic response mainly in energy and nitrogen uptake, stress response, amino acid conversion, and cell wall thickness. Indeed, data reported here show that resistance to cationic antimicrobial peptides possesses a greater molecular complexity than previously supposed, resulting in cell commitment to several metabolic pathways.
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95
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Onyango LA, Dunstan RH, Gottfries J, von Eiff C, Roberts TK. Effect of low temperature on growth and ultra-structure of Staphylococcus spp. PLoS One 2012; 7:e29031. [PMID: 22291884 PMCID: PMC3265459 DOI: 10.1371/journal.pone.0029031] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/12/2011] [Accepted: 11/19/2011] [Indexed: 11/18/2022] Open
Abstract
The effect of temperature fluctuation is an important factor in bacterial growth especially for pathogens such as the staphylococci that have to remain viable during potentially harsh and prolonged transfer conditions between hosts. The aim of this study was to investigate the response of S. aureus, S. epidermidis, and S. lugdunensis when exposed to low temperature (4°C) for prolonged periods, and how this factor affected their subsequent growth, colony morphology, cellular ultra-structure, and amino acid composition in the non-cytoplasmic hydrolysate fraction. Clinical isolates were grown under optimal conditions and then subjected to 4°C conditions for a period of 8 wks. Cold-stressed and reference control samples were assessed under transmission electron microscopy (TEM) to identify potential ultra-structural changes. To determine changes in amino acid composition, cells were fractured to remove the lipid and cytoplasmic components and the remaining structural components were hydrolysed. Amino acid profiles for the hydrolysis fraction were then analysed for changes by using principal component analysis (PCA). Exposure of the three staphylococci to prolonged low temperature stress resulted in the formation of increasing proportions of small colony variant (SCV) phenotypes. TEM revealed that SCV cells had significantly thicker and more diffuse cell-walls than their corresponding WT samples for both S. aureus and S. epidermidis, but the changes were not significant for S. lugdunensis. Substantial species-specific alterations in the amino acid composition of the structural hydrolysate fraction were also observed in the cold-treated cells. The data indicated that the staphylococci responded over prolonged periods of cold-stress treatment by transforming into SCV populations. The observed ultra-structural and amino acid changes were proposed to represent response mechanisms for staphylococcal survival amidst hostile conditions, thus maintaining the viability of the species until favourable conditions arise again.
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Affiliation(s)
- Laura A. Onyango
- Environmental and Pathogenic Microbiology Laboratory, School of Environmental and Life Sciences, University of Newcastle, Newcastle, New South Wales, Australia
| | - R. Hugh Dunstan
- Environmental and Pathogenic Microbiology Laboratory, School of Environmental and Life Sciences, University of Newcastle, Newcastle, New South Wales, Australia
- * E-mail:
| | - Johan Gottfries
- Department of Chemistry, Gothenburg University, Gothenburg, Sweden
| | - Christof von Eiff
- Institute of Medical Microbiology, University of Münster, Münster, Germany
| | - Timothy K. Roberts
- Environmental and Pathogenic Microbiology Laboratory, School of Environmental and Life Sciences, University of Newcastle, Newcastle, New South Wales, Australia
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96
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TODA H, YAMAGUCHI T, MIYARA T, HISATO A, MATSUSHIMA T, SHIMADA T, SANO H, NAKAE K, KAMISAKO T. Clinical Microbiological Investigation of Vancomycin Intermediate Staphylococcus aureus During Glycopeptide Therapy. ACTA ACUST UNITED AC 2012; 86:734-40. [DOI: 10.11150/kansenshogakuzasshi.86.734] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
Affiliation(s)
- Hirofumi TODA
- Department of Clinical Laboratory, Kinki University Hospital
- Infection Control Team, Kinki University Hospital
| | - Toshihiro YAMAGUCHI
- Department of Clinical Laboratory, Kinki University Hospital
- Infection Control Team, Kinki University Hospital
| | - Takayuki MIYARA
- Department of Medical Safety Administration, Kinki University Hospital
- Infection Control Team, Kinki University Hospital
| | - Akihiro HISATO
- Department of Pharmacy, Kinki University Hospital
- Infection Control Team, Kinki University Hospital
| | - Tomohide MATSUSHIMA
- Critical care Medical Center, Kinki University Hospital
- Infection Control Team, Kinki University Hospital
| | - Takahiro SHIMADA
- Division of Hematology and Rheumatology, Department of Internal Medicine, Kinki University Faculty of Medicine
- Infection Control Team, Kinki University Hospital
| | - Hiroyuki SANO
- Department of Respiratory Medicine and Allergology, Kinki University Faculty of Medicine
- Infection Control Team, Kinki University Hospital
| | - Kenichi NAKAE
- Department of Clinical Laboratory, Kinki University Hospital
| | - Toshinori KAMISAKO
- Department of Clinical Laboratory, Kinki University Hospital
- Department of Clinical Laboratory Medicine, Kinki University Faculty of Medicine
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97
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Haag NL, Velk KK, Wu C. Potential Antibacterial Targets in Bacterial Central Metabolism. INTERNATIONAL JOURNAL ON ADVANCES IN LIFE SCIENCES 2012; 4:21-32. [PMID: 24151543 PMCID: PMC3800682] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
The emerging antibiotic resistant bacteria and their abilities for rapid evolution have pushed the need to explore alternative antibiotics less prone to drug resistance. In this study, we employed methicillin/multidrug-resistant Staphylococcus aureus (MRSA) as a model bacterial system to initiate novel antibiotic development. An in silico identification of drug targets in MRSA 252 strain and MRSA Mu50 strain respectively was described. The identified potential targets were classified according to their known or putative functions. We discovered that a class of essential non-human homologous, central metabolic enzymes falls into the scope of potential drug targets for two reasons: 1) the identified targets either do not have human counterparts or use alternative catalytic mechanisms. Based on major differences in active site structure and catalytic mechanism, an inhibitor of such a bacterial enzyme can be designed which will not inhibit its human cousin. 2) attacking bacterial energy-making machinery bypasses the usual drug resistance sites, paving the road to multi-faceted approaches to combat antibiotic resistance.
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Affiliation(s)
- Nichole Louise Haag
- Division of Natural Sciences Mount Marty College 1105 W 8th St. Yankton, the United States
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98
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Moreillon P, Bizzini A, Giddey M, Vouillamoz J, Entenza JM. Vancomycin-intermediate Staphylococcus aureus selected during vancomycin therapy of experimental endocarditis are not detected by culture-based diagnostic procedures and persist after treatment arrest. J Antimicrob Chemother 2011; 67:652-60. [PMID: 22167243 DOI: 10.1093/jac/dkr521] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
OBJECTIVES Laboratory detection of vancomycin-intermediate Staphylococcus aureus (VISA) and their heterogeneous VISA (hVISA) precursors is difficult. Thus, it is possible that vancomycin failures against supposedly vancomycin-susceptible S. aureus are due to undiagnosed VISA or hVISA. We tested this hypothesis in experimental endocarditis. METHODS Rats with aortic valve infection due to the vancomycin-susceptible (MIC 2 mg/L), methicillin-resistant S. aureus M1V2 were treated for 2 days with doses of vancomycin that mimicked the pharmacokinetics seen in humans following intravenous administration of 1 g of the drug every 12 h. Half of the treated animals were killed 8 h after treatment arrest and half 3 days thereafter. Population analyses were done directly on vegetation homogenates or after one subculture in drug-free medium to mimic standard diagnostic procedures. RESULTS Vancomycin cured 14 of 26 animals (54%; P<0.05 versus controls) after 2 days of treatment. When vegetation homogenates were plated directly on vancomycin-containing plates, 6 of 13 rats killed 8 h after treatment arrest had positive cultures, 1 of which harboured hVISA. Likewise, 6 of 13 rats killed 3 days thereafter had positive valve cultures, 5 of which harboured hVISA. However, one subculture of vegetations in drug-free broth was enough to revert all the hVISA phenotypes to the susceptible pattern of the parent. Thus, vancomycin selected for hVISA during therapy of experimental endocarditis due to vancomycin-susceptible S. aureus. These hVISA were associated with vancomycin failure. The hVISA phenotype persisted in vivo, even after vancomycin arrest, but was missed in vitro after a single passage of the vegetation homogenate on drug-free medium. CONCLUSIONS hVISA might escape detection in clinical samples if they are subcultured before susceptibility tests.
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Affiliation(s)
- Philippe Moreillon
- Department of Fundamental Microbiology, University of Lausanne, Lausanne, Switzerland
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99
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TAKAGI S, HAYASHI S, TAKAHASHI K, ISOGAI H, BAI L, YONEYAMA H, ANDO T, ITO K, ISOGAI E. Antimicrobial activity of a bovine myeloid antimicrobial peptide (BMAP-28) against methicillin-susceptible and methicillin-resistant Staphylococcus aureus. Anim Sci J 2011; 83:482-6. [DOI: 10.1111/j.1740-0929.2011.00979.x] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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100
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Howden BP, McEvoy CRE, Allen DL, Chua K, Gao W, Harrison PF, Bell J, Coombs G, Bennett-Wood V, Porter JL, Robins-Browne R, Davies JK, Seemann T, Stinear TP. Evolution of multidrug resistance during Staphylococcus aureus infection involves mutation of the essential two component regulator WalKR. PLoS Pathog 2011; 7:e1002359. [PMID: 22102812 PMCID: PMC3213104 DOI: 10.1371/journal.ppat.1002359] [Citation(s) in RCA: 240] [Impact Index Per Article: 18.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2011] [Accepted: 09/21/2011] [Indexed: 11/18/2022] Open
Abstract
Antimicrobial resistance in Staphylococcus aureus is a major public health threat, compounded by emergence of strains with resistance to vancomycin and daptomycin, both last line antimicrobials. Here we have performed high throughput DNA sequencing and comparative genomics for five clinical pairs of vancomycin-susceptible (VSSA) and vancomycin-intermediate ST239 S. aureus (VISA); each pair isolated before and after vancomycin treatment failure. These comparisons revealed a frequent pattern of mutation among the VISA strains within the essential walKR two-component regulatory locus involved in control of cell wall metabolism. We then conducted bi-directional allelic exchange experiments in our clinical VSSA and VISA strains and showed that single nucleotide substitutions within either walK or walR lead to co-resistance to vancomycin and daptomycin, and caused the typical cell wall thickening observed in resistant clinical isolates. Ion Torrent genome sequencing confirmed no additional regulatory mutations had been introduced into either the walR or walK VISA mutants during the allelic exchange process. However, two potential compensatory mutations were detected within putative transport genes for the walK mutant. The minimal genetic changes in either walK or walR also attenuated virulence, reduced biofilm formation, and led to consistent transcriptional changes that suggest an important role for this regulator in control of central metabolism. This study highlights the dramatic impacts of single mutations that arise during persistent S. aureus infections and demonstrates the role played by walKR to increase drug resistance, control metabolism and alter the virulence potential of this pathogen.
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Affiliation(s)
- Benjamin P Howden
- Department of Microbiology and Immunology, University of Melbourne, Victoria, Australia.
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