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Seier-Petersen MA, Jasni A, Aarestrup FM, Vigre H, Mullany P, Roberts AP, Agersø Y. Effect of subinhibitory concentrations of four commonly used biocides on the conjugative transfer of Tn916 in Bacillus subtilis. J Antimicrob Chemother 2013; 69:343-8. [PMID: 24092655 PMCID: PMC3886932 DOI: 10.1093/jac/dkt370] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Objectives Large amounts of biocides are used to reduce and control bacterial growth in the healthcare sector, food production and agriculture. This work explores the effect of subinhibitory concentrations of four commonly used biocides (ethanol, hydrogen peroxide, chlorhexidine digluconate and sodium hypochlorite) on the conjugative transposition of the mobile genetic element Tn916. Methods Conjugation assays were carried out between Bacillus subtilis strains. The donor containing Tn916 was pre-exposed to subinhibitory concentrations of each biocide for a defined length of time, which was determined by an analysis of the transcriptional response of the promoter upstream of tet(M) using β-glucuronidase reporter assays. Results Ethanol significantly (P = 0.01) increased the transfer of Tn916 by 5-fold, whereas hydrogen peroxide, chlorhexidine digluconate and sodium hypochlorite did not significantly affect the transfer frequency. Conclusions These results suggest that exposure to subinhibitory concentrations of ethanol may induce the transfer of Tn916-like elements and any resistance genes they contain.
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Affiliation(s)
- M A Seier-Petersen
- Division for Epidemiology and Microbial Genomics, National Food Institute, Technical University of Denmark, Kgs. Lyngby, Denmark
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152
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Specificity in suppression of SOS expression by recA4162 and uvrD303. DNA Repair (Amst) 2013; 12:1072-80. [PMID: 24084169 DOI: 10.1016/j.dnarep.2013.09.003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2013] [Revised: 08/29/2013] [Accepted: 09/04/2013] [Indexed: 01/15/2023]
Abstract
Detection and repair of DNA damage is essential in all organisms and depends on the ability of proteins recognizing and processing specific DNA substrates. In E. coli, the RecA protein forms a filament on single-stranded DNA (ssDNA) produced by DNA damage and induces the SOS response. Previous work has shown that one type of recA mutation (e.g., recA4162 (I298V)) and one type of uvrD mutation (e.g., uvrD303 (D403A, D404A)) can differentially decrease SOS expression depending on the type of inducing treatments (UV damage versus RecA mutants that constitutively express SOS). Here it is tested using other SOS inducing conditions if there is a general feature of ssDNA generated during these treatments that allows recA4162 and uvrD303 to decrease SOS expression. The SOS inducing conditions tested include growing cells containing temperature-sensitive DNA replication mutations (dnaE486, dnaG2903, dnaN159, dnaZ2016 (at 37°C)), a del(polA)501 mutation and induction of Double-Strand Breaks (DSBs). uvrD303 could decrease SOS expression under all conditions, while recA4162 could decrease SOS expression under all conditions except in the polA strain or when DSBs occur. It is hypothesized that recA4162 suppresses SOS expression best when the ssDNA occurs at a gap and that uvrD303 is able to decrease SOS expression when the ssDNA is either at a gap or when it is generated at a DSB (but does so better at a gap).
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153
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Mukonzo JK, Namuwenge PM, Okure G, Mwesige B, Namusisi OK, Mukanga D. Over-the-counter suboptimal dispensing of antibiotics in Uganda. J Multidiscip Healthc 2013; 6:303-10. [PMID: 23990728 PMCID: PMC3753154 DOI: 10.2147/jmdh.s49075] [Citation(s) in RCA: 39] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Background Overuse and misuse of antibiotics is a serious global problem. While resistance to older antibiotics is increasing, development of newer molecules has stalled. Resistance to the existing antibiotics that is largely driven by their high-volume use is a global public health problem. Uganda is one of the countries where prescription-only drugs, including antibiotics, can be obtained over the counter. We determined the rate of antibiotic dispensing and use in Uganda. Methods The study utilized a descriptive cross-sectional study design to determine the number of antibiotic “prescribed” daily doses per 1,000 clients. Data were collected from one health center II, eight general/district hospitals, one national referral hospital, and 62 registered community pharmacies. From each study site, data were collected for five consecutive days over the months of November 2011 to January 2012. Results The overall antibiotic issue rate was 43.2%. Amoxicillin, metronidazole, ciprofloxacin, sulfamethoxazole–trimethoprim, cloxacillin, and ampicillin, belonging to the WHO anatomical therapeutic chemical classifications of penicillin with extended spectra, imidazole derivatives, fluoroquinolones, and sulfonamide–trimethoprim combinations, constituted 70% of the issued antibiotics. About 41% of antibiotics were issued over the counter. At community pharmacies, where 30% of antibiotic dispensing occurred, the number of prescribed daily doses/1,000 antibiotic clients was 4,169 compared to 6,220, 7,350 and 7,500 at general/district hospitals, the national referral hospital, and the health center, respectively. Conclusion In Uganda, at least four in every ten individuals that visit a health-care facility are treated with an antibiotic. Antibiotics are largely given as over-the-counter drugs at community pharmacies. The number of antibiotic prescribed daily doses/1,000 antibiotic clients does not significantly differ between categories of health-care facilities except at community pharmacies, where lower doses are dispensed compared to other health-care facilities.
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Affiliation(s)
- Jackson K Mukonzo
- Center for Operational Research Africa, Kampala, Uganda ; Department of Pharmacology and Therapeutics, Uganda
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154
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Sun CL, Relman DA. Microbiota's 'little helpers': bacteriophages and antibiotic-associated responses in the gut microbiome. Genome Biol 2013; 14:127. [PMID: 23906048 PMCID: PMC4053952 DOI: 10.1186/gb-2013-14-7-127] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023] Open
Abstract
Antibiotics alter the abundance and types of bacteriophage-associated genes in the mouse gut, suggesting that phage help bacterial communities during times of stress.
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155
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Multiple Pathways of Genome Plasticity Leading to Development of Antibiotic Resistance. Antibiotics (Basel) 2013; 2:288-315. [PMID: 27029305 PMCID: PMC4790341 DOI: 10.3390/antibiotics2020288] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/07/2013] [Revised: 05/21/2013] [Accepted: 05/23/2013] [Indexed: 02/05/2023] Open
Abstract
The emergence of multi-resistant bacterial strains is a major source of concern and has been correlated with the widespread use of antibiotics. The origins of resistance are intensively studied and many mechanisms involved in resistance have been identified, such as exogenous gene acquisition by horizontal gene transfer (HGT), mutations in the targeted functions, and more recently, antibiotic tolerance through persistence. In this review, we focus on factors leading to integron rearrangements and gene capture facilitating antibiotic resistance acquisition, maintenance and spread. The role of stress responses, such as the SOS response, is discussed.
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156
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Compensation of the metabolic costs of antibiotic resistance by physiological adaptation in Escherichia coli. Antimicrob Agents Chemother 2013; 57:3752-62. [PMID: 23716056 DOI: 10.1128/aac.02096-12] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Antibiotic resistance is often associated with metabolic costs. To investigate the metabolic consequences of antibiotic resistance, the genomic and transcriptomic profiles of an amoxicillin-resistant Escherichia coli strain and the wild type it was derived from were compared. A total of 125 amino acid substitutions and 7 mutations that were located <1,000 bp upstream of differentially expressed genes were found in resistant cells. However, broad induction and suppression of genes were observed when comparing the expression profiles of resistant and wild-type cells. Expression of genes involved in cell wall maintenance, DNA metabolic processes, cellular stress response, and respiration was most affected in resistant cells regardless of the absence or presence of amoxicillin. The SOS response was downregulated in resistant cells. The physiological effect of the acquisition of amoxicillin resistance in cells grown in chemostat cultures consisted of an initial increase in glucose consumption that was followed by an adaptation process. Furthermore, no difference in maintenance energy was observed between resistant and sensitive cells. In accordance with the transcriptomic profile, exposure of resistant cells to amoxicillin resulted in reduced salt and pH tolerance. Taken together, the results demonstrate that the acquisition of antibiotic resistance in E. coli is accompanied by specifically reorganized metabolic networks in order to circumvent metabolic costs. The overall effect of the acquisition of resistance consists not so much of an extra energy requirement, but more a reduced ecological range.
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157
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Xia G, Wolz C. Phages of Staphylococcus aureus and their impact on host evolution. INFECTION GENETICS AND EVOLUTION 2013; 21:593-601. [PMID: 23660485 DOI: 10.1016/j.meegid.2013.04.022] [Citation(s) in RCA: 134] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/03/2013] [Revised: 03/25/2013] [Accepted: 04/18/2013] [Indexed: 01/01/2023]
Abstract
Most of the dissimilarity between Staphylococcus aureus strains is due to the presence of mobile genetic elements such as bacteriophages or pathogenicity islands. These elements provide the bacteria with additional genes that enable them to establish a new lifestyle that is often accompanied by a shift to increased pathogenicity or a jump to a new host. S. aureus phages may carry genes coding for diverse virulence factors such as Panton-Valentine leukocidin, staphylokinase, enterotoxins, chemotaxis-inhibitory proteins, or exfoliative toxins. Phages also mediate the transfer of pathogenicity islands in a highly coordinated manner and are the primary vehicle for the horizontal transfer of chromosomal and extra-chromosomal genes. Here, we summarise recent advances regarding phage classification, genome organisation and function of S. aureus phages with a particular emphasis on their role in the evolution of the bacterial host.
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Affiliation(s)
- Guoqing Xia
- Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, Elfriede-Aulhornstrasse-6, 72076 Tübingen, Germany; German Center for Infection Research (DZIF), Tübingen, Germany
| | - Christiane Wolz
- Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, Elfriede-Aulhornstrasse-6, 72076 Tübingen, Germany.
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158
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Abstract
Bacteriophages, or simply phages, are viruses infecting bacteria. With an estimated 1031 particles in the biosphere, phages outnumber bacteria by a factor of at least 10 and not surprisingly, they influence the evolution of most bacterial species, sometimes in unexpected ways. “Temperate” phages have the ability to integrate into the chromosome of their host upon infection, where they can reside as “quiescent” prophages until conditions favor their reactivation. Lysogenic conversion resulting from the integration of prophages encoding powerful toxins is probably the most determinant contribution of prophages to the evolution of pathogenic bacteria. We currently grasp only a small fraction of the total phage diversity. Phage biologists keep unraveling novel mechanisms developed by phages to parasitize their host. The purpose of this review is to give an overview of some of the various ways by which prophages change the lifestyle and boost virulence of some of the most dangerous bacterial pathogens.
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Affiliation(s)
- Louis-Charles Fortier
- Département de Microbiologie et d'Infectiologie, Faculté de Médecine et des Sciences de la Santé, Université de Sherbrooke, Sherbrooke, QC Canada.
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159
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Plata KB, Riosa S, Singh CR, Rosato RR, Rosato AE. Targeting of PBP1 by β-lactams determines recA/SOS response activation in heterogeneous MRSA clinical strains. PLoS One 2013; 8:e61083. [PMID: 23637786 PMCID: PMC3634065 DOI: 10.1371/journal.pone.0061083] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/27/2012] [Accepted: 03/06/2013] [Indexed: 11/19/2022] Open
Abstract
The SOS response, a conserved regulatory network in bacteria that is induced in response to DNA damage, has been shown to be associated with the emergence of resistance to antibiotics. Previously, we demonstrated that heterogeneous (HeR) MRSA strains, when exposed to sub-inhibitory concentrations of oxacillin, were able to express a homogeneous high level of resistance (HoR). Moreover, we showed that oxacillin appeared to be the triggering factor of a β-lactam-mediated SOS response through lexA/recA regulators, responsible for an increased mutation rate and selection of a HoR derivative. In this work, we demonstrated, by selectively exposing to β-lactam and non-β-lactam cell wall inhibitors, that PBP1 plays a critical role in SOS-mediated recA activation and HeR-HoR selection. Functional analysis of PBP1 using an inducible PBP1-specific antisense construct showed that PBP1 depletion abolished both β-lactam-induced recA expression/activation and increased mutation rates during HeR/HoR selection. Furthermore, based on the observation that HeR/HoR selection is accompanied by compensatory increases in the expression of PBP1,-2, -2a, and -4, our study provides evidence that a combination of agents simultaneously targeting PBP1 and either PBP2 or PBP2a showed both in-vitro and in-vivo efficacy, thereby representing a therapeutic option for the treatment of highly resistant HoR-MRSA strains. The information gathered from these studies contributes to our understanding of β-lactam-mediated HeR/HoR selection and provides new insights, based on β-lactam synergistic combinations, that mitigate drug resistance for the treatment of MRSA infections.
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Affiliation(s)
- Konrad B. Plata
- Department of Pathology and Genomic Medicine, The Methodist Hospital, Houston, Texas, United States of America
- Center for Molecular and Translational Human Infectious Diseases Research, The Methodist Hospital Research Institute, Houston, Texas, United States of America
| | - Sarah Riosa
- Department of Pathology and Genomic Medicine, The Methodist Hospital, Houston, Texas, United States of America
- Center for Molecular and Translational Human Infectious Diseases Research, The Methodist Hospital Research Institute, Houston, Texas, United States of America
| | - Christopher R. Singh
- Department of Pathology and Genomic Medicine, The Methodist Hospital, Houston, Texas, United States of America
- Center for Molecular and Translational Human Infectious Diseases Research, The Methodist Hospital Research Institute, Houston, Texas, United States of America
| | - Roberto R. Rosato
- Department of Pathology and Genomic Medicine, The Methodist Hospital, Houston, Texas, United States of America
- Center for Molecular and Translational Human Infectious Diseases Research, The Methodist Hospital Research Institute, Houston, Texas, United States of America
| | - Adriana E. Rosato
- Department of Pathology and Genomic Medicine, The Methodist Hospital, Houston, Texas, United States of America
- Center for Molecular and Translational Human Infectious Diseases Research, The Methodist Hospital Research Institute, Houston, Texas, United States of America
- * E-mail:
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160
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Beceiro A, Tomás M, Bou G. Antimicrobial resistance and virulence: a successful or deleterious association in the bacterial world? Clin Microbiol Rev 2013; 26:185-230. [PMID: 23554414 PMCID: PMC3623377 DOI: 10.1128/cmr.00059-12] [Citation(s) in RCA: 616] [Impact Index Per Article: 56.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Hosts and bacteria have coevolved over millions of years, during which pathogenic bacteria have modified their virulence mechanisms to adapt to host defense systems. Although the spread of pathogens has been hindered by the discovery and widespread use of antimicrobial agents, antimicrobial resistance has increased globally. The emergence of resistant bacteria has accelerated in recent years, mainly as a result of increased selective pressure. However, although antimicrobial resistance and bacterial virulence have developed on different timescales, they share some common characteristics. This review considers how bacterial virulence and fitness are affected by antibiotic resistance and also how the relationship between virulence and resistance is affected by different genetic mechanisms (e.g., coselection and compensatory mutations) and by the most prevalent global responses. The interplay between these factors and the associated biological costs depend on four main factors: the bacterial species involved, virulence and resistance mechanisms, the ecological niche, and the host. The development of new strategies involving new antimicrobials or nonantimicrobial compounds and of novel diagnostic methods that focus on high-risk clones and rapid tests to detect virulence markers may help to resolve the increasing problem of the association between virulence and resistance, which is becoming more beneficial for pathogenic bacteria.
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161
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Bernier SP, Lebeaux D, DeFrancesco AS, Valomon A, Soubigou G, Coppée JY, Ghigo JM, Beloin C. Starvation, together with the SOS response, mediates high biofilm-specific tolerance to the fluoroquinolone ofloxacin. PLoS Genet 2013; 9:e1003144. [PMID: 23300476 PMCID: PMC3536669 DOI: 10.1371/journal.pgen.1003144] [Citation(s) in RCA: 174] [Impact Index Per Article: 15.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2012] [Accepted: 10/22/2012] [Indexed: 12/14/2022] Open
Abstract
High levels of antibiotic tolerance are a hallmark of bacterial biofilms. In contrast to well-characterized inherited antibiotic resistance, molecular mechanisms leading to reversible and transient antibiotic tolerance displayed by biofilm bacteria are still poorly understood. The physiological heterogeneity of biofilms influences the formation of transient specialized subpopulations that may be more tolerant to antibiotics. In this study, we used random transposon mutagenesis to identify biofilm-specific tolerant mutants normally exhibited by subpopulations located in specialized niches of heterogeneous biofilms. Using Escherichia coli as a model organism, we demonstrated, through identification of amino acid auxotroph mutants, that starved biofilms exhibited significantly greater tolerance towards fluoroquinolone ofloxacin than their planktonic counterparts. We demonstrated that the biofilm-associated tolerance to ofloxacin was fully dependent on a functional SOS response upon starvation to both amino acids and carbon source and partially dependent on the stringent response upon leucine starvation. However, the biofilm-specific ofloxacin increased tolerance did not involve any of the SOS-induced toxin–antitoxin systems previously associated with formation of highly tolerant persisters. We further demonstrated that ofloxacin tolerance was induced as a function of biofilm age, which was dependent on the SOS response. Our results therefore show that the SOS stress response induced in heterogeneous and nutrient-deprived biofilm microenvironments is a molecular mechanism leading to biofilm-specific high tolerance to the fluoroquinolone ofloxacin. Biofilm surface-attached communities have the capacity to tolerate high concentrations of antibiotics, and bacterial biofilms formed on indwelling medical devices are difficult to eradicate and often lead to the onset of chronic or systemic infections. The physiological heterogeneity of multicellular biofilms has been associated with development of subpopulations highly tolerant to multiple antibiotics. Here we demonstrate that, upon starvation for specific essential growth nutrients, biofilm bacteria become highly tolerant to fluoroquinolone ofloxacin. The SOS response plays a critical role in this phenomenon, while the stringent response plays only a minor role. Taken together, these results support the hypothesis that bacteria localized within nutrient-limited niches of the biofilm structure may temporarily enter a physiological state enabling them to tolerate bactericidal concentrations of antibiotics.
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Affiliation(s)
- Steve P. Bernier
- Institut Pasteur, Unité de Génétique des Biofilms, Paris, France
| | - David Lebeaux
- Institut Pasteur, Unité de Génétique des Biofilms, Paris, France
| | | | - Amandine Valomon
- Institut Pasteur, Unité de Génétique des Biofilms, Paris, France
| | - Guillaume Soubigou
- Institut Pasteur, Génopole, Plate-forme 2–Transcriptome et Epigénome, Paris, France
| | - Jean-Yves Coppée
- Institut Pasteur, Génopole, Plate-forme 2–Transcriptome et Epigénome, Paris, France
| | - Jean-Marc Ghigo
- Institut Pasteur, Unité de Génétique des Biofilms, Paris, France
| | - Christophe Beloin
- Institut Pasteur, Unité de Génétique des Biofilms, Paris, France
- * E-mail:
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162
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Schröder W, Goerke C, Wolz C. Opposing effects of aminocoumarins and fluoroquinolones on the SOS response and adaptability in Staphylococcus aureus. J Antimicrob Chemother 2012; 68:529-38. [PMID: 23169893 DOI: 10.1093/jac/dks456] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
OBJECTIVES RecA is the key enzyme involved in DNA repair, recombination and induction of the SOS response and is central to the development of antibiotic resistance. Here we assessed the interaction of two different gyrase inhibitors, ciprofloxacin (a fluoroquinolone) and novobiocin (an aminocoumarin), on RecA activity and the SOS response in Staphylococcus aureus. METHODS The influence of different gyrase inhibitors on the SOS response of S. aureus (including recA and lexA mutants) was analysed by northern blot analysis, real-time RT-PCR, western blot analysis and promoter activity assays. Recombination as well as mutation frequencies were determined for the different antibiotic combinations. RESULTS We verified that ciprofloxacin leads to RecA activation and therefore induction of the SOS response. In contrast, novobiocin treatment resulted in an inhibition of recA transcription independent of LexA. When novobiocin and ciprofloxacin were added simultaneously, recA was reduced to the same level as with novobiocin alone. In combination, novobiocin also partially reduces the ciprofloxacin-mediated induction of the LexA target gene umuC (error-prone polymerase). Apart from reducing recA and umuC expression, novobiocin also inhibited the frequency of recombination, mutation and the formation of non-haemolytic variants. CONCLUSION In summary, aminocoumarins inhibit recA expression in S. aureus and probably delay the process of developing antibiotic resistance and gene transfer. A clinical re-evaluation of these compounds as well as designing more applicable derivatives should be considered.
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Affiliation(s)
- Wiebke Schröder
- Interfaculty Institute of Microbiology and Infection Medicine, University of Tübingen, Elfriede-Aulhorn-Strasse-6, 72076 Tübingen, Germany
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163
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Dalhoff A. Global fluoroquinolone resistance epidemiology and implictions for clinical use. Interdiscip Perspect Infect Dis 2012; 2012:976273. [PMID: 23097666 PMCID: PMC3477668 DOI: 10.1155/2012/976273] [Citation(s) in RCA: 212] [Impact Index Per Article: 17.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2012] [Accepted: 06/26/2012] [Indexed: 12/22/2022] Open
Abstract
This paper on the fluoroquinolone resistance epidemiology stratifies the data according to the different prescription patterns by either primary or tertiary caregivers and by indication. Global surveillance studies demonstrate that fluoroquinolone resistance rates increased in the past years in almost all bacterial species except S. pneumoniae and H. influenzae, causing community-acquired respiratory tract infections. However, 10 to 30% of these isolates harbored first-step mutations conferring low level fluoroquinolone resistance. Fluoroquinolone resistance increased in Enterobacteriaceae causing community acquired or healthcare associated urinary tract infections and intraabdominal infections, exceeding 50% in some parts of the world, particularly in Asia. One to two-thirds of Enterobacteriaceae producing extended spectrum β-lactamases were fluoroquinolone resistant too. Furthermore, fluoroquinolones select for methicillin resistance in Staphylococci. Neisseria gonorrhoeae acquired fluoroquinolone resistance rapidly; actual resistance rates are highly variable and can be as high as almost 100%, particularly in Asia, whereas resistance rates in Europe and North America range from <10% in rural areas to >30% in established sexual networks. In general, the continued increase in fluoroquinolone resistance affects patient management and necessitates changes in some guidelines, for example, treatment of urinary tract, intra-abdominal, skin and skin structure infections, and traveller's diarrhea, or even precludes the use in indications like sexually transmitted diseases and enteric fever.
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Affiliation(s)
- Axel Dalhoff
- Institute for Infection-Medicine, Christian-Albrechts Univerity of Kiel and University Medical Center Schleswig-Holstein, Brunswiker Straße 4, 24105 Kiel, Germany
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164
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Yitzhaki S, Rostron JE, Xu Y, Rideout MC, Authement RN, Barlow SB, Segall AM. Similarities between exogenously- and endogenously-induced envelope stress: the effects of a new antibacterial molecule, TPI1609-10. PLoS One 2012; 7:e44896. [PMID: 23071502 PMCID: PMC3469575 DOI: 10.1371/journal.pone.0044896] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2012] [Accepted: 08/15/2012] [Indexed: 11/19/2022] Open
Abstract
Antibiotics with novel and/or multiple targets are highly desirable in the face of the steady rise of clinical antibiotic resistance. We have screened and identified small molecules, typified by the compound TPI1609-10 (aka SM10), with antibiotic activity against both gram-positive and gram-negative bacteria. SM10 was screened in vitro to bind branched Holliday junction intermediates of homologous recombination and tyrosine recombinase-mediated recombination; thus, the cellular targets of the small molecules were expected to include the RuvABC Holliday junction resolvasome and the XerCD complex involved in proper segregation of replicated chromosomes to daughter cells. SM10 indeed induces DNA damage and filamentation in E. coli. However, SM10 also induces envelope stress and causes increased production of intracellular reactive oxygen species. In addition, SM10 has similar effects to endogenously-induced envelope stress via overproducing outer membrane proteins (OmpC and OmpF), which also induces the SOS response, chromosome fragmentation, and production of reactive oxygen species. The synergy between SM10, and cerulenin, a fatty acid synthesis inhibitor, together with the SM10 hypersensitivity of cpx and rpoE mutants, further support that SM10's mode of action damages membrane damage. The lethality of SM10 treatment and of OmpC overproduction are observed in both aerobically- and anaerobically-grown cells, and is accompanied by substantial DNA damage even anaerobically. Thus, only some DNA damage is due to reactive oxygen. We propose that membrane depolarization and the potential reduction in intracellular pH, leading to abasic site formation, cause a substantial amount of the DNA damage associated with both SM10 treatment and endogenous envelope stress. While it is difficult to completely exclude effects related to envelope damage as the sources of DNA damage, trapping intermediates associated with DNA repair and chromosome segregation pathways remains very likely. Thus SM10 may have distinct but synergistic modes of action.
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Affiliation(s)
- Shmuel Yitzhaki
- Department of Biology and Center for Microbial Sciences, San Diego State University, San Diego, California, United States of America
| | - Jason E. Rostron
- Department of Biology and Center for Microbial Sciences, San Diego State University, San Diego, California, United States of America
| | - Yan Xu
- Department of Biology and Center for Microbial Sciences, San Diego State University, San Diego, California, United States of America
| | - Marc C. Rideout
- Department of Biology and Center for Microbial Sciences, San Diego State University, San Diego, California, United States of America
| | - R. Nathan Authement
- Department of Biology and Center for Microbial Sciences, San Diego State University, San Diego, California, United States of America
| | - Steven B. Barlow
- Department of Biology and Center for Microbial Sciences, San Diego State University, San Diego, California, United States of America
- Electron Microscopy Facility, San Diego State University, San Diego, California, United States of America
| | - Anca M. Segall
- Department of Biology and Center for Microbial Sciences, San Diego State University, San Diego, California, United States of America
- * E-mail:
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165
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Duan C, Zhu L, Xu Y, Lau GW. Saturated alanine scanning mutagenesis of the pneumococcus competence stimulating peptide identifies analogs that inhibit genetic transformation. PLoS One 2012; 7:e44710. [PMID: 23028586 PMCID: PMC3441458 DOI: 10.1371/journal.pone.0044710] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/20/2012] [Accepted: 08/07/2012] [Indexed: 11/29/2022] Open
Abstract
Antibiotic resistance is a major challenge to modern medicine. Intraspecies and interspecies dissemination of antibiotic resistance genes among bacteria can occur through horizontal gene transfer. Competence-mediated gene transfer has been reported to contribute to the spread of antibiotic resistance genes in Streptococcus pneumoniae. Induction of the competence regulon is mediated by a 17-amino acid peptide pheromone called the competence stimulating peptide (CSP). Thus, synthetic analogs that competitively inhibit CSPs may reduce horizontal gene transfer. We performed saturated alanine scanning mutagenesis and other amino acid substitutions on CSP1 to screen for analogs that disable genetic transformation in S. pneumoniae. Substitution of the glutamate residue at the first position created analogs that could competitively inhibit CSP1-mediated competence development in a concentration-dependent manner. Additional substitutions of the negatively-charged glutamate residue with amino acids of different charge, acidity and hydrophobicity, as well as enantiomeric D-glutamate, generated analogs that efficiently outcompeted CSP1, suggesting the importance of negative charge and enantiomericity of the first glutamate residue for the function of CSP1. Collectively, these results indicate that glutamate residue at the first position is important for the ability of CSP1 to induce ComD, but is dispensable for the peptide to bind the receptor. Furthermore, these results demonstrate the potential applicability of competitive CSP analogs to control horizontal transfer of antibiotic resistance genes in S. pneumoniae.
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Affiliation(s)
- Chaohui Duan
- Department of Pathobiology, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
- Laboratory of Clinical Immunology, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, Guangdong, People’s Republic of China
| | - Luchang Zhu
- Department of Pathobiology, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
| | - Ying Xu
- Department of Pathobiology, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
- Laboratory of Clinical Immunology, Sun Yat-Sen Memorial Hospital, Sun Yat-Sen University, Guangzhou, Guangdong, People’s Republic of China
| | - Gee W. Lau
- Department of Pathobiology, University of Illinois at Urbana-Champaign, Urbana, Illinois, United States of America
- * E-mail:
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166
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Spilman MS, Damle PK, Dearborn AD, Rodenburg CM, Chang JR, Wall EA, Christie GE, Dokland T. Assembly of bacteriophage 80α capsids in a Staphylococcus aureus expression system. Virology 2012; 434:242-50. [PMID: 22980502 DOI: 10.1016/j.virol.2012.08.031] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2012] [Revised: 08/20/2012] [Accepted: 08/22/2012] [Indexed: 11/26/2022]
Abstract
80α is a temperate, double-stranded DNA bacteriophage of Staphylococcus aureus that can act as a "helper" for the mobilization of S. aureus pathogenicity islands (SaPIs), including SaPI1. When SaPI1 is mobilized by 80α, the SaPI genomes are packaged into capsids that are composed of phage proteins, but that are smaller than those normally formed by the phage. This size determination is dependent on SaPI1 proteins CpmA and CpmB. Here, we show that co-expression of the 80α capsid and scaffolding proteins in S. aureus, but not in E. coli, leads to the formation of procapsid-related structures, suggesting that a host co-factor is required for assembly. The capsid and scaffolding proteins also undergo normal N-terminal processing upon expression in S. aureus, implicating a host protease. We also find that SaPI1 proteins CpmA and CpmB promote the formation of small capsids upon co-expression with 80α capsid and scaffolding proteins in S. aureus.
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Affiliation(s)
- Michael S Spilman
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL 35294, USA
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167
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Evidence of in vivo prophage induction during Clostridium difficile infection. Appl Environ Microbiol 2012; 78:7662-70. [PMID: 22923402 DOI: 10.1128/aem.02275-12] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Prophages contribute to the evolution and virulence of most bacterial pathogens, but their role in Clostridium difficile is unclear. Here we describe the isolation of four Myoviridae phages, ΦMMP01, ΦMMP02, ΦMMP03, and ΦMMP04, that were recovered as free viral particles in the filter-sterilized stool supernatants of patients suffering from C. difficile infection (CDI). Furthermore, identical prophages were found in the chromosomes of C. difficile isolated from the corresponding fecal samples. We therefore provide, for the first time, evidence of in vivo prophage induction during CDI. We completely sequenced the genomes of ΦMMP02 and ΦMMP04, and bioinformatics analyses did not reveal the presence of virulence factors but underlined the unique character of ΦMMP04. We also studied the mobility of ΦMMP02 and ΦMMP04 prophages in vitro. Both prophages were spontaneously induced, with 4 to 5 log PFU/ml detected in the culture supernatants of the corresponding lysogens. When lysogens were grown in the presence of subinhibitory concentrations of ciprofloxacin, moxifloxacin, levofloxacin, or mitomycin C, the phage titers further increased, reaching 8 to 9 log PFU/ml in the case of ΦMMP04. In summary, our study highlights the extensive genetic diversity and mobility of C. difficile prophages. Moreover, antibiotics known to represent risk factors for CDI, such as quinolones, can stimulate prophage mobility in vitro and probably in vivo as well, which underscores their potential impact on phage-mediated horizontal gene transfer events and the evolution of C. difficile.
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168
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Quinto-Alemany D, Canerina-Amaro A, Hernández-Abad LG, Machín F, Romesberg FE, Gil-Lamaignere C. Yeasts acquire resistance secondary to antifungal drug treatment by adaptive mutagenesis. PLoS One 2012; 7:e42279. [PMID: 22860105 PMCID: PMC3409178 DOI: 10.1371/journal.pone.0042279] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2012] [Accepted: 07/02/2012] [Indexed: 11/19/2022] Open
Abstract
Acquisition of resistance secondary to treatment both by microorganisms and by tumor cells is a major public health concern. Several species of bacteria acquire resistance to various antibiotics through stress-induced responses that have an adaptive mutagenesis effect. So far, adaptive mutagenesis in yeast has only been described when the stress is nutrient deprivation. Here, we hypothesized that adaptive mutagenesis in yeast (Saccharomyces cerevisiae and Candida albicans as model organisms) would also take place in response to antifungal agents (5-fluorocytosine or flucytosine, 5-FC, and caspofungin, CSP), giving rise to resistance secondary to treatment with these agents. We have developed a clinically relevant model where both yeasts acquire resistance when exposed to these agents. Stressful lifestyle associated mutation (SLAM) experiments show that the adaptive mutation frequencies are 20 (S. cerevisiae -5-FC), 600 (C. albicans -5-FC) or 1000 (S. cerevisiae--CSP) fold higher than the spontaneous mutation frequency, the experimental data for C. albicans -5-FC being in agreement with the clinical data of acquisition of resistance secondary to treatment. The spectrum of mutations in the S. cerevisiae -5-FC model differs between spontaneous and acquired, indicating that the molecular mechanisms that generate them are different. Remarkably, in the acquired mutations, an ectopic intrachromosomal recombination with an 87% homologous gene takes place with a high frequency. In conclusion, we present here a clinically relevant adaptive mutation model that fulfils the conditions reported previously.
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Affiliation(s)
- David Quinto-Alemany
- Unidad de Investigación. Hospital Universitario Nuestra Señora de Candelaria, Santa Cruz de Tenerife, Spain
| | - Ana Canerina-Amaro
- Unidad de Investigación. Hospital Universitario Nuestra Señora de Candelaria, Santa Cruz de Tenerife, Spain
| | - Luís G. Hernández-Abad
- Unidad de Investigación. Hospital Universitario Nuestra Señora de Candelaria, Santa Cruz de Tenerife, Spain
| | - Félix Machín
- Unidad de Investigación. Hospital Universitario Nuestra Señora de Candelaria, Santa Cruz de Tenerife, Spain
| | - Floyd E. Romesberg
- Chemistry Department, The Scripps Research Institute, La Jolla, California, United States of America
| | - Cristina Gil-Lamaignere
- Unidad de Investigación. Hospital Universitario Nuestra Señora de Candelaria, Santa Cruz de Tenerife, Spain
- * E-mail:
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169
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Abstract
Plants, animals, bacteria, and Archaea all have evolved mechanisms to cope with environmental or cellular stress. Bacterial cells respond to the stress of DNA damage by activation of the SOS response, the canonical RecA/LexA-dependent signal transduction pathway that transcriptionally derepresses a multiplicity of genes-leading to transient arrest of cell division and initiation of DNA repair. Here we report the previously unsuspected role of E. coli endoribonuclease RNase E in regulation of the SOS response. We show that RNase E deletion or inactivation of temperature-sensitive RNase E protein precludes normal initiation of SOS. The ability of RNase E to regulate SOS is dynamic, as down regulation of RNase E following DNA damage by mitomycin C resulted in SOS termination and restoration of RNase E function leads to resumption of a previously aborted response. Overexpression of the RraA protein, which binds to the C-terminal region of RNase E and modulates the actions of degradosomes, recapitulated the effects of RNase E deficiency. Possible mechanisms for RNase E effects on SOS are discussed.
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170
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Muthaiyan A, Martin EM, Natesan S, Crandall PG, Wilkinson BJ, Ricke SC. Antimicrobial effect and mode of action of terpeneless cold-pressed Valencia orange essential oil on methicillin-resistant Staphylococcus aureus. J Appl Microbiol 2012; 112:1020-33. [PMID: 22372962 DOI: 10.1111/j.1365-2672.2012.05270.x] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
AIMS The objectives of this study were to evaluate the antistaphylococcal effect and elucidate the mechanism of action of orange essential oil against antibiotic-resistant Staphylococcus aureus strains. METHODS AND RESULTS The inhibitory effect of commercial orange essential oil (EO) against six Staph. aureus strains was tested using disc diffusion and agar dilution methods. The mechanism of EO action on MRSA was analysed by transcriptional profiling. Morphological changes of EO-treated Staph. aureus were examined using transmission electron microscopy. Results showed that 0·1% of terpeneless cold-pressed Valencia orange oil (CPV) induced the cell wall stress stimulon consistent with the inhibition of cell wall synthesis. Transmission electron microscopic observation revealed cell lysis and suggested a cell wall lysis-related mechanism of CPV. CONCLUSIONS CPV inhibits the growth of Staph. aureus, causes gene expression changes consistent with the inhibition of cell wall synthesis, and triggers cell lysis. SIGNIFICANCE AND IMPACT OF THE STUDY Multiple antibiotics resistance is becoming a serious problem in the management of Staph. aureus infections. In this study, the altered expression of cell wall-associated genes and subsequent cell lysis in MRSA caused by CPV suggest that it may be a potential antimicrobial agent to control antibiotic-resistant Staph. aureus.
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Affiliation(s)
- A Muthaiyan
- Center for Food Safety and Department of Food Science, University of Arkansas, Fayetteville, AR 72704, USA
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171
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Gaupp R, Ledala N, Somerville GA. Staphylococcal response to oxidative stress. Front Cell Infect Microbiol 2012; 2:33. [PMID: 22919625 PMCID: PMC3417528 DOI: 10.3389/fcimb.2012.00033] [Citation(s) in RCA: 146] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2012] [Accepted: 02/29/2012] [Indexed: 12/23/2022] Open
Abstract
Staphylococci are a versatile genus of bacteria that are capable of causing acute and chronic infections in diverse host species. The success of staphylococci as pathogens is due in part to their ability to mitigate endogenous and exogenous oxidative and nitrosative stress. Endogenous oxidative stress is a consequence of life in an aerobic environment; whereas, exogenous oxidative and nitrosative stress are often due to the bacteria's interaction with host immune systems. To overcome the deleterious effects of oxidative and nitrosative stress, staphylococci have evolved protection, detoxification, and repair mechanisms that are controlled by a network of regulators. In this review, we summarize the cellular targets of oxidative stress, the mechanisms by which staphylococci sense oxidative stress and damage, oxidative stress protection and repair mechanisms, and regulation of the oxidative stress response. When possible, special attention is given to how the oxidative stress defense mechanisms help staphylococci control oxidative stress in the host.
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Affiliation(s)
- Rosmarie Gaupp
- School of Veterinary Medicine and Biomedical Sciences, University of Nebraska-Lincoln, Lincoln NE, USA
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172
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Nanoalumina promotes the horizontal transfer of multiresistance genes mediated by plasmids across genera. Proc Natl Acad Sci U S A 2012; 109:4944-9. [PMID: 22411796 DOI: 10.1073/pnas.1107254109] [Citation(s) in RCA: 298] [Impact Index Per Article: 24.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Antibiotic resistance is a worldwide public health concern. Conjugative transfer between closely related strains or species of bacteria is an important method for the horizontal transfer of multidrug-resistance genes. The extent to which nanomaterials are able to cause an increase in antibiotic resistance by the regulation of the conjugative transfer of antibiotic-resistance genes in bacteria, especially across genera, is still unknown. Here we show that nanomaterials in water can significantly promote the horizontal conjugative transfer of multidrug-resistance genes mediated by the RP4, RK2, and pCF10 plasmids. Nanoalumina can promote the conjugative transfer of the RP4 plasmid from Escherichia coli to Salmonella spp. by up to 200-fold compared with untreated cells. We also explored the mechanisms behind this phenomenon and demonstrate that nanoalumina is able to induce oxidative stress, damage bacterial cell membranes, enhance the expression of mating pair formation genes and DNA transfer and replication genes, and depress the expression of global regulatory genes that regulate the conjugative transfer of RP4. These findings are important in assessing the risk of nanomaterials to the environment, particularly from water and wastewater treatment systems, and in the estimation of the effect of manufacture and use of nanomaterials on the environment.
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173
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McCarthy AJ, Witney AA, Lindsay JA. Staphylococcus aureus temperate bacteriophage: carriage and horizontal gene transfer is lineage associated. Front Cell Infect Microbiol 2012; 2:6. [PMID: 22919598 PMCID: PMC3417521 DOI: 10.3389/fcimb.2012.00006] [Citation(s) in RCA: 78] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2011] [Accepted: 01/23/2012] [Indexed: 12/27/2022] Open
Abstract
Staphylococcus aureus is a major cause of human and animal infections. Bacteriophage are a class of mobile genetic element (MGE) that carry virulence genes and disseminate them horizontally, including Panton–Valentine leukocidin (PVL), the immune evasion cluster (IEC) associated with human specificity, and enterotoxin A the major toxin associated with food poisoning. S. aureus isolates group into major clonal complex (CC) lineages that largely evolve independently due to possession of different restriction–modification (RM) systems. We aimed to better understand the horizontal and vertical transmission dynamics of virulence and resistance genes by bacteriophage by using (i) bioinformatic approaches to analyze bacteriophage genomes from the first 79 sequenced S. aureus isolates and (ii) S. aureus microarrays to analyze the distribution of bacteriophage and virulence genes in S. aureus isolates from a broader range of lineages. The distribution of eight bacteriophage families was highly variable but lineage associated. Nevertheless, there was evidence of frequent acquisition and loss and not just vertical transmission. Most bacteriophage genes were dispensable, and extensive mosaicism was seen. Surprisingly, virulence genes were tightly associated with specific phage families. This data suggests S. aureus bacteriophage evolve rapidly, and the horizontal gene transfer (HGT) of virulence genes encoded by bacteriophage is restricted by bacteriophage family and the lineage of the host bacterium, delaying the evolution of fully resistant and virulent strains.
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Affiliation(s)
- Alex J McCarthy
- Division of Clinical Sciences, Centre for Infection, St George's University of London London, UK.
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174
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Sanchez-Alberola N, Campoy S, Barbé J, Erill I. Analysis of the SOS response of Vibrio and other bacteria with multiple chromosomes. BMC Genomics 2012; 13:58. [PMID: 22305460 PMCID: PMC3323433 DOI: 10.1186/1471-2164-13-58] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2011] [Accepted: 02/03/2012] [Indexed: 12/18/2022] Open
Abstract
Background The SOS response is a well-known regulatory network present in most bacteria and aimed at addressing DNA damage. It has also been linked extensively to stress-induced mutagenesis, virulence and the emergence and dissemination of antibiotic resistance determinants. Recently, the SOS response has been shown to regulate the activity of integrases in the chromosomal superintegrons of the Vibrionaceae, which encompasses a wide range of pathogenic species harboring multiple chromosomes. Here we combine in silico and in vitro techniques to perform a comparative genomics analysis of the SOS regulon in the Vibrionaceae, and we extend the methodology to map this transcriptional network in other bacterial species harboring multiple chromosomes. Results Our analysis provides the first comprehensive description of the SOS response in a family (Vibrionaceae) that includes major human pathogens. It also identifies several previously unreported members of the SOS transcriptional network, including two proteins of unknown function. The analysis of the SOS response in other bacterial species with multiple chromosomes uncovers additional regulon members and reveals that there is a conserved core of SOS genes, and that specialized additions to this basic network take place in different phylogenetic groups. Our results also indicate that across all groups the main elements of the SOS response are always found in the large chromosome, whereas specialized additions are found in the smaller chromosomes and plasmids. Conclusions Our findings confirm that the SOS response of the Vibrionaceae is strongly linked with pathogenicity and dissemination of antibiotic resistance, and suggest that the characterization of the newly identified members of this regulon could provide key insights into the pathogenesis of Vibrio. The persistent location of key SOS genes in the large chromosome across several bacterial groups confirms that the SOS response plays an essential role in these organisms and sheds light into the mechanisms of evolution of global transcriptional networks involved in adaptability and rapid response to environmental changes, suggesting that small chromosomes may act as evolutionary test beds for the rewiring of transcriptional networks.
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Affiliation(s)
- Neus Sanchez-Alberola
- Departament de Genètica i de Microbiologia, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain
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175
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Drudge CN, Warren LA. Prokaryotic Horizontal Gene Transfer in Freshwater Lakes: Implications of Dynamic Biogeochemical Zonation. ACTA ACUST UNITED AC 2012. [DOI: 10.4236/jep.2012.312181] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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176
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Rasigade JP, Moulay A, Lhoste Y, Tristan A, Bes M, Vandenesch F, Etienne J, Lina G, Laurent F, Dumitrescu O. Impact of sub-inhibitory antibiotics on fibronectin-mediated host cell adhesion and invasion by Staphylococcus aureus. BMC Microbiol 2011; 11:263. [PMID: 22168812 PMCID: PMC3264541 DOI: 10.1186/1471-2180-11-263] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2011] [Accepted: 12/14/2011] [Indexed: 11/28/2022] Open
Abstract
Background Staphylococcus aureus is a well-armed pathogen prevalent in severe infections such as endocarditis and osteomyelitis. Fibronectin-binding proteins A and B, encoded by fnbA/B, are major pathogenesis determinants in these infections through their involvement in S. aureus adhesion to and invasion of host cells. Sub-minimum inhibitory concentrations (sub-MICs) of antibiotics, frequently occurring in vivo because of impaired drug diffusion at the infection site, can alter S. aureus phenotype. We therefore investigated their impact on S. aureus fibronectin-mediated adhesiveness and invasiveness. Methods After in vitro challenge of S. aureus 8325-4 and clinical isolates with sub-MICs of major anti-staphylococcal agents, we explored fnbA/B transcription levels, bacterial adhesiveness to immobilised human fibronectin and human osteoblasts in culture, and bacterial invasion of human osteoblasts. Results Oxacillin, moxifloxacin and linezolid led to the development of a hyper-adhesive phenotype in the fibronectin adhesion assay that was consistent with an increase in fnbA/B transcription. Conversely, rifampin treatment decreased fibronectin binding in all strains tested without affecting fnbA/B transcription. Gentamicin and vancomycin had no impact on fibronectin binding or fnbA/B transcription levels. Only oxacillin-treated S. aureus displayed a significantly increased adhesion to cultured osteoblasts, but its invasiveness did not differ from that of untreated controls. Conclusion Our findings demonstrate that several antibiotics at sub-MICs modulate fibronectin binding in S. aureus in a drug-specific fashion. However, hyper- and hypo- adhesive phenotypes observed in controlled in vitro conditions were not fully confirmed in whole cell infection assays. The relevance of adhesion modulation during in vivo infections is thus still uncertain and requires further investigations.
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Abstract
Antibiotics are a cost-effective tool for improving feed efficiency and preventing disease in agricultural animals, but the full scope of their collateral effects is not understood. Antibiotics have been shown to mediate gene transfer by inducing prophages in certain bacterial strains; therefore, one collateral effect could be prophage induction in the gut microbiome at large. Here we used metagenomics to evaluate the effect of two antibiotics in feed (carbadox and ASP250 [chlortetracycline, sulfamethazine, and penicillin]) on swine intestinal phage metagenomes (viromes). We also monitored the bacterial communities using 16S rRNA gene sequencing. ASP250, but not carbadox, caused significant population shifts in both the phage and bacterial communities. Antibiotic resistance genes, such as multidrug resistance efflux pumps, were identified in the viromes, but in-feed antibiotics caused no significant changes in their abundance. The abundance of phage integrase-encoding genes was significantly increased in the viromes of medicated swine over that in the viromes of nonmedicated swine, demonstrating the induction of prophages with antibiotic treatment. Phage-bacterium population dynamics were also examined. We observed a decrease in the relative abundance of Streptococcus bacteria (prey) when Streptococcus phages (predators) were abundant, supporting the “kill-the-winner” ecological model of population dynamics in the swine fecal microbiome. The data show that gut ecosystem dynamics are influenced by phages and that prophage induction is a collateral effect of in-feed antibiotics. This study advances our knowledge of the collateral effects of in-feed antibiotics at a time in which the widespread use of “growth-promoting” antibiotics in agriculture is under scrutiny. Using comparative metagenomics, we show that prophages are induced by in-feed antibiotics in swine fecal microbiomes and that antibiotic resistance genes were detected in most viromes. This suggests that in-feed antibiotics are contributing to phage-mediated gene transfer, potentially of antibiotic resistance genes, in the swine gut. Additionally, the so-called “kill-the-winner” model of phage-bacterium population dynamics has been shown in aquatic ecosystems but met with conflicting evidence in gut ecosystems. The data support the idea that swine fecal Streptococcus bacteria and their phages follow the kill-the-winner model. Understanding the role of phages in gut microbial ecology is an essential component of the antibiotic resistance problem and of developing potential mitigation strategies.
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179
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Skippington E, Ragan MA. Lateral genetic transfer and the construction of genetic exchange communities. FEMS Microbiol Rev 2011; 35:707-35. [DOI: 10.1111/j.1574-6976.2010.00261.x] [Citation(s) in RCA: 123] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
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180
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Aminov RI. Horizontal gene exchange in environmental microbiota. Front Microbiol 2011; 2:158. [PMID: 21845185 PMCID: PMC3145257 DOI: 10.3389/fmicb.2011.00158] [Citation(s) in RCA: 354] [Impact Index Per Article: 27.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2011] [Accepted: 07/11/2011] [Indexed: 01/21/2023] Open
Abstract
Horizontal gene transfer (HGT) plays an important role in the evolution of life on the Earth. This view is supported by numerous occasions of HGT that are recorded in the genomes of all three domains of living organisms. HGT-mediated rapid evolution is especially noticeable among the Bacteria, which demonstrate formidable adaptability in the face of recent environmental changes imposed by human activities, such as the use of antibiotics, industrial contamination, and intensive agriculture. At the heart of the HGT-driven bacterial evolution and adaptation are highly sophisticated natural genetic engineering tools in the form of a variety of mobile genetic elements (MGEs). The main aim of this review is to give a brief account of the occurrence and diversity of MGEs in natural ecosystems and of the environmental factors that may affect MGE-mediated HGT.
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Affiliation(s)
- Rustam I Aminov
- Rowett Institute of Nutrition and Health, University of Aberdeen Aberdeen, UK
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181
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Cambray G, Sanchez-Alberola N, Campoy S, Guerin É, Da Re S, González-Zorn B, Ploy MC, Barbé J, Mazel D, Erill I. Prevalence of SOS-mediated control of integron integrase expression as an adaptive trait of chromosomal and mobile integrons. Mob DNA 2011; 2:6. [PMID: 21529368 PMCID: PMC3108266 DOI: 10.1186/1759-8753-2-6] [Citation(s) in RCA: 96] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2010] [Accepted: 04/30/2011] [Indexed: 11/26/2022] Open
Abstract
Background Integrons are found in hundreds of environmental bacterial species, but are mainly known as the agents responsible for the capture and spread of antibiotic-resistance determinants between Gram-negative pathogens. The SOS response is a regulatory network under control of the repressor protein LexA targeted at addressing DNA damage, thus promoting genetic variation in times of stress. We recently reported a direct link between the SOS response and the expression of integron integrases in Vibrio cholerae and a plasmid-borne class 1 mobile integron. SOS regulation enhances cassette swapping and capture in stressful conditions, while freezing the integron in steady environments. We conducted a systematic study of available integron integrase promoter sequences to analyze the extent of this relationship across the Bacteria domain. Results Our results showed that LexA controls the expression of a large fraction of integron integrases by binding to Escherichia coli-like LexA binding sites. In addition, the results provide experimental validation of LexA control of the integrase gene for another Vibrio chromosomal integron and for a multiresistance plasmid harboring two integrons. There was a significant correlation between lack of LexA control and predicted inactivation of integrase genes, even though experimental evidence also indicates that LexA regulation may be lost to enhance expression of integron cassettes. Conclusions Ancestral-state reconstruction on an integron integrase phylogeny led us to conclude that the ancestral integron was already regulated by LexA. The data also indicated that SOS regulation has been actively preserved in mobile integrons and large chromosomal integrons, suggesting that unregulated integrase activity is selected against. Nonetheless, additional adaptations have probably arisen to cope with unregulated integrase activity. Identifying them may be fundamental in deciphering the uneven distribution of integrons in the Bacteria domain.
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Affiliation(s)
- Guillaume Cambray
- Institut Pasteur, Unité Plasticité du Génome Bactérien, CNRS URA 2171, 75015 Paris, France
| | - Neus Sanchez-Alberola
- Departament de Genètica i de Microbiologia, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain.,Department of Biological Sciences, University of Maryland Baltimore County, Baltimore 21228, USA
| | - Susana Campoy
- Departament de Genètica i de Microbiologia, Universitat Autònoma de Barcelona, 08193 Bellaterra, Spain
| | - Émilie Guerin
- Université de Limoges, Faculté de Médecine, EA3175, INSERM, Equipe Avenir, Limoges 87000, France
| | - Sandra Da Re
- Université de Limoges, Faculté de Médecine, EA3175, INSERM, Equipe Avenir, Limoges 87000, France
| | - Bruno González-Zorn
- Departamento de Sanidad Animal, Facultad de Veterinaria, and VISAVET, Universidad Complutense de Madrid, 28040 Madrid, Spain
| | - Marie-Cécile Ploy
- Université de Limoges, Faculté de Médecine, EA3175, INSERM, Equipe Avenir, Limoges 87000, France
| | - Jordi Barbé
- Department of Biological Sciences, University of Maryland Baltimore County, Baltimore 21228, USA
| | - Didier Mazel
- Institut Pasteur, Unité Plasticité du Génome Bactérien, CNRS URA 2171, 75015 Paris, France
| | - Ivan Erill
- Department of Biological Sciences, University of Maryland Baltimore County, Baltimore 21228, USA
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Beta-lactams interfering with PBP1 induce Panton-Valentine leukocidin expression by triggering sarA and rot global regulators of Staphylococcus aureus. Antimicrob Agents Chemother 2011; 55:3261-71. [PMID: 21502633 DOI: 10.1128/aac.01401-10] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Previous articles reported that beta-lactam antibiotics increase the expression of Staphylococcus aureus Panton-Valentine leukocidin (PVL) by activating its transcription. We investigated the mechanisms underlying the inductor effect of beta-lactams on PVL expression by determining targets and regulatory pathways possibly implicated in this process. We measured PVL production in the presence of oxacillin (nonselective), imipenem (penicillin-binding protein 1 [PBP1] selective), cefotaxime (PBP2 selective), cefaclore (PBP3 selective), and cefoxitin (PBP4 selective). In vitro, we observed increased PVL production consistent with luk-PV mRNA levels that were 20 to 25 times higher for community-acquired methicillin-resistant S. aureus (CA-MRSA) cultures treated with PBP1-binding oxacillin and imipenem than for cultures treated with other beta-lactams or no antibiotic at all. This effect was also observed in vivo, with increased PVL mRNA levels in lung tissues from CA-MRSA-infected mice treated with imipenem but not cefoxitin. To confirm the involvement of PBP1 inhibition in this pathway, PBP1 depletion by use of an inducible pbp1 antisense RNA showed a dose-dependent relationship between the level of pbp1 antisense RNA and the luk-PV mRNA level. Upon imipenem treatment of exponential-phase cultures, we observed an increased sarA mRNA level after 30 min of incubation followed by a decreased rot mRNA level after 1 to 4 h of incubation. Unlike the agr and saeRS positive regulators, which were nonessential for PVL induction by beta-lactams, the sarA (positive) and rot (negative) PVL regulators were necessary for PVL induction by imipenem. Our results suggest that antibiotics binding to PBP1 increase PVL expression by modulating sarA and rot, which are essential mediators of the inductor effect of beta-lactams on PVL expression.
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183
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Bacterial SOS response: a food safety perspective. Curr Opin Biotechnol 2011; 22:136-42. [DOI: 10.1016/j.copbio.2010.11.012] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2010] [Revised: 11/17/2010] [Accepted: 11/23/2010] [Indexed: 11/19/2022]
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Rosado H, Rahman KM, Feuerbaum EA, Hinds J, Thurston DE, Taylor PW. The minor groove-binding agent ELB-21 forms multiple interstrand and intrastrand covalent cross-links with duplex DNA and displays potent bactericidal activity against methicillin-resistant Staphylococcus aureus. J Antimicrob Chemother 2011; 66:985-96. [PMID: 21393142 PMCID: PMC3073633 DOI: 10.1093/jac/dkr044] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Objectives The antistaphylococcal pyrrolobenzodiazepine dimer ELB-21 forms multiple adducts with duplex DNA through covalent interactions with appropriately spaced guanine residues; it is now known to form interstrand and intrastrand adducts with oligonucleotide sequences of variable length. We determined the DNA sequence preferences of ELB-21 in relation to its capacity to exert a bactericidal effect by damaging DNA. Methods Formation of adducts by ELB-21 and 12- to 14-mer DNA duplexes was investigated using ion-pair reversed phase liquid chromatography and mass spectrometry. Drug-induced changes in gene expression were measured in prophage-free Staphylococcus aureus RN4220 by microarray analysis. Results ELB-21 preferentially formed intrastrand adducts with guanines separated by three nucleotide base pairs. Interstrand and intrastrand adducts were formed with duplexes both longer and shorter than the preferred target sequences. ELB-21 elicited rapid bactericidal effects against prophage-carrying and prophage-free S. aureus strains; cell lysis occurred following activation and release of resident prophages. Killing appeared to be due to irreparable damage to bacterial DNA and susceptibility to ELB-21 was governed by the capacity of staphylococci to repair DNA lesions through induction of the SOS DNA damage response mediated by the RecA-LexA pathway. Conclusions The data support the contention that ELB-21 arrests DNA replication, eliciting formation of ssDNA-RecA filaments that inactivate LexA, the SOS repressor, and phage repressors such as Cl, resulting in activation of the DNA damage response and de-repression of resident prophages. Above the MIC threshold, DNA repair is ineffective.
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Affiliation(s)
- Helena Rosado
- School of Pharmacy, University of London, London, UK
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185
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Jolivet-Gougeon A, Kovacs B, Le Gall-David S, Le Bars H, Bousarghin L, Bonnaure-Mallet M, Lobel B, Guillé F, Soussy CJ, Tenke P. Bacterial hypermutation: clinical implications. J Med Microbiol 2011; 60:563-573. [PMID: 21349992 DOI: 10.1099/jmm.0.024083-0] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/24/2023] Open
Abstract
Heritable hypermutation in bacteria is mainly due to alterations in the methyl-directed mismatch repair (MMR) system. MMR-deficient strains have been described from several bacterial species, and all of the strains exhibit increased mutation frequency and recombination, which are important mechanisms for acquired drug resistance in bacteria. Antibiotics select for drug-resistant strains and refine resistance determinants on plasmids, thus stimulating DNA recombination via the MMR system. Antibiotics can also act as indirect promoters of antibiotic resistance by inducing the SOS system and certain error-prone DNA polymerases. These alterations have clinical consequences in that efficacious treatment of bacterial infections requires high doses of antibiotics and/or a combination of different classes of antimicrobial agents. There are currently few new drugs with low endogenous resistance potential, and the development of such drugs merits further research.
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Affiliation(s)
- Anne Jolivet-Gougeon
- Equipe Microbiologie, UPRES-EA 1254, Pontchaillou Teaching Hospital and Faculté des Sciences Pharmaceutiques et Biologiques, Université de Rennes I, Université Européenne de Bretagne, 2 avenue du Professeur Léon Bernard, 35043 Rennes, France
| | - Bela Kovacs
- Department of Urology, Jahn Ferenc Del-Pesti Hospital, Koves ut 2, 1204 Budapest, Hungary
| | - Sandrine Le Gall-David
- Equipe Microbiologie, UPRES-EA 1254, Pontchaillou Teaching Hospital and Faculté des Sciences Pharmaceutiques et Biologiques, Université de Rennes I, Université Européenne de Bretagne, 2 avenue du Professeur Léon Bernard, 35043 Rennes, France
| | - Hervé Le Bars
- Equipe Microbiologie, UPRES-EA 1254, Pontchaillou Teaching Hospital and Faculté des Sciences Pharmaceutiques et Biologiques, Université de Rennes I, Université Européenne de Bretagne, 2 avenue du Professeur Léon Bernard, 35043 Rennes, France
| | - Latifa Bousarghin
- Equipe Microbiologie, UPRES-EA 1254, Pontchaillou Teaching Hospital and Faculté des Sciences Pharmaceutiques et Biologiques, Université de Rennes I, Université Européenne de Bretagne, 2 avenue du Professeur Léon Bernard, 35043 Rennes, France
| | - Martine Bonnaure-Mallet
- Equipe Microbiologie, UPRES-EA 1254, Pontchaillou Teaching Hospital and Faculté des Sciences Pharmaceutiques et Biologiques, Université de Rennes I, Université Européenne de Bretagne, 2 avenue du Professeur Léon Bernard, 35043 Rennes, France
| | - Bernard Lobel
- Service d'Urologie, CHU Pontchaillou, 2 rue Henri Le Guilloux, 35033 Rennes cedex 9, France
| | - François Guillé
- Service d'Urologie, CHU Pontchaillou, 2 rue Henri Le Guilloux, 35033 Rennes cedex 9, France
| | - Claude-James Soussy
- Service de Bactériologie-Virologie-Hygiène, CHU Henri-Mondor, 51 avenue du Maréchal-de-Lattre-de-Tassigny, 94010 Créteil cedex, France
| | - Peter Tenke
- Department of Urology, Jahn Ferenc Del-Pesti Hospital, Koves ut 2, 1204 Budapest, Hungary
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186
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Vibrio cholerae triggers SOS and mutagenesis in response to a wide range of antibiotics: a route towards multiresistance. Antimicrob Agents Chemother 2011; 55:2438-41. [PMID: 21300836 DOI: 10.1128/aac.01549-10] [Citation(s) in RCA: 148] [Impact Index Per Article: 11.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Antibiotic resistance development has been linked to the bacterial SOS stress response. In Escherichia coli, fluoroquinolones are known to induce SOS, whereas other antibiotics, such as aminoglycosides, tetracycline, and chloramphenicol, do not. Here we address whether various antibiotics induce SOS in Vibrio cholerae. Reporter green fluorescent protein (GFP) fusions were used to measure the response of SOS-regulated promoters to subinhibitory concentrations of antibiotics. We show that unlike the situation with E. coli, all these antibiotics induce SOS in V. cholerae.
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187
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Soil Phage Ecology: Abundance, Distribution, and Interactions with Bacterial Hosts. SOIL BIOLOGY 2011. [DOI: 10.1007/978-3-642-14512-4_4] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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188
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Cohn MT, Kjelgaard P, Frees D, Penadés JR, Ingmer H. Clp-dependent proteolysis of the LexA N-terminal domain in Staphylococcus aureus. MICROBIOLOGY-SGM 2010; 157:677-684. [PMID: 21183573 DOI: 10.1099/mic.0.043794-0] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
The SOS response is governed by the transcriptional regulator LexA and is elicited in many bacterial species in response to DNA damaging conditions. Induction of the SOS response is mediated by autocleavage of the LexA repressor resulting in a C-terminal dimerization domain (CTD) and an N-terminal DNA-binding domain (NTD) known to retain some DNA-binding activity. The proteases responsible for degrading the LexA domains have been identified in Escherichia coli as ClpXP and Lon. Here, we show that in the human and animal pathogen Staphylococcus aureus, the ClpXP and ClpCP proteases contribute to degradation of the NTD and to a lesser degree the CTD. In the absence of the proteolytic subunit, ClpP, or one or both of the Clp ATPases, ClpX and ClpC, the LexA domains were stabilized after autocleavage. Production of a stabilized variant of the NTD interfered with mitomycin-mediated induction of sosA expression while leaving lexA unaffected, and also significantly reduced SOS-induced mutagenesis. Our results show that sequential proteolysis of LexA is conserved in S. aureus and that the NTD may differentially regulate a subset of genes in the SOS regulon.
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Affiliation(s)
- Marianne T Cohn
- Department of Veterinary Disease Biology, Faculty of Life Sciences, University of Copenhagen, Stigbøjlen 4, DK-1870 Frederiksberg C, Denmark
| | - Peter Kjelgaard
- Department of Veterinary Disease Biology, Faculty of Life Sciences, University of Copenhagen, Stigbøjlen 4, DK-1870 Frederiksberg C, Denmark
| | - Dorte Frees
- Department of Veterinary Disease Biology, Faculty of Life Sciences, University of Copenhagen, Stigbøjlen 4, DK-1870 Frederiksberg C, Denmark
| | - José R Penadés
- Departamento de Quimica, Bioquimica y Biologia Molecular, Universidad Cardenal Herrera-CEU, Moncada, Valencia 46113, Spain.,Centro Investigación y Tecnologia Animal, Instituto Valenciano de Investigaciones Agrarias (CITA-IVIA), Apdo 187, Segorbe, Castellón, Spain
| | - Hanne Ingmer
- Department of Veterinary Disease Biology, Faculty of Life Sciences, University of Copenhagen, Stigbøjlen 4, DK-1870 Frederiksberg C, Denmark
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189
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Spilman MS, Dearborn AD, Chang JR, Damle PK, Christie GE, Dokland T. A conformational switch involved in maturation of Staphylococcus aureus bacteriophage 80α capsids. J Mol Biol 2010; 405:863-76. [PMID: 21129380 DOI: 10.1016/j.jmb.2010.11.047] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/05/2010] [Revised: 11/22/2010] [Accepted: 11/23/2010] [Indexed: 10/18/2022]
Abstract
Bacteriophages are involved in many aspects of the spread and establishment of virulence factors in Staphylococcus aureus, including the mobilization of genetic elements known as S. aureus pathogenicity islands (SaPIs), which carry genes for superantigen toxins and other virulence factors. SaPIs are packaged into phage-like transducing particles using proteins supplied by the helper phage. We have used cryo-electron microscopy and icosahedral reconstruction to determine the structures of the procapsid and the mature capsid of 80α, a bacteriophage that can mobilize several different SaPIs. The 80α capsid has T=7 icosahedral symmetry with the capsid protein organized into pentameric and hexameric clusters that interact via prominent trimeric densities. The 80α capsid protein was modeled based on the capsid protein fold of bacteriophage HK97 and fitted into the 80α reconstructions. The models show that the trivalent interactions are mediated primarily by a 22-residue β hairpin structure called the P loop that is not found in HK97. Capsid expansion is associated with a conformational switch in the spine helix that is propagated throughout the subunit, unlike the domain rotation mechanism in phage HK97 or P22.
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Affiliation(s)
- Michael S Spilman
- Department of Microbiology, University of Alabama at Birmingham, Birmingham, AL 35294, USA
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190
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Christie GE, Matthews AM, King DG, Lane KD, Olivarez NP, Tallent SM, Gill SR, Novick RP. The complete genomes of Staphylococcus aureus bacteriophages 80 and 80α--implications for the specificity of SaPI mobilization. Virology 2010; 407:381-90. [PMID: 20869739 DOI: 10.1016/j.virol.2010.08.036] [Citation(s) in RCA: 62] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2010] [Revised: 08/22/2010] [Accepted: 08/31/2010] [Indexed: 11/19/2022]
Abstract
Staphylococcus aureus pathogenicity islands (SaPIs) are mobile elements that are induced by a helper bacteriophage to excise and replicate and to be encapsidated in phage-like particles smaller than those of the helper, leading to high-frequency transfer. SaPI mobilization is helper phage specific; only certain SaPIs can be mobilized by a particular helper phage. Staphylococcal phage 80α can mobilize every SaPI tested thus far, including SaPI1, SaPI2 and SaPIbov1. Phage 80, on the other hand, cannot mobilize SaPI1, and ϕ11 mobilizes only SaPIbov1. In order to better understand the relationship between SaPIs and their helper phages, the genomes of phages 80 and 80α were sequenced, compared with other staphylococcal phage genomes, and analyzed for unique features that may be involved in SaPI mobilization.
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Affiliation(s)
- G E Christie
- Department of Microbiology and Immunology, Virginia Commonwealth University School of Medicine, 1101 E Marshall Street; PO Box 980678, Richmond, VA 23298-0678, USA.
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191
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Malachowa N, DeLeo FR. Mobile genetic elements of Staphylococcus aureus. Cell Mol Life Sci 2010; 67:3057-71. [PMID: 20668911 PMCID: PMC2929429 DOI: 10.1007/s00018-010-0389-4] [Citation(s) in RCA: 328] [Impact Index Per Article: 23.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2010] [Revised: 04/06/2010] [Accepted: 04/26/2010] [Indexed: 01/30/2023]
Abstract
Bacteria such as Staphylococcus aureus are successful as commensal organisms or pathogens in part because they adapt rapidly to selective pressures imparted by the human host. Mobile genetic elements (MGEs) play a central role in this adaptation process and are a means to transfer genetic information (DNA) among and within bacterial species. Importantly, MGEs encode putative virulence factors and molecules that confer resistance to antibiotics, including the gene that confers resistance to beta-lactam antibiotics in methicillin-resistant S. aureus (MRSA). Inasmuch as MRSA infections are a significant problem worldwide and continue to emerge in epidemic waves, there has been significant effort to improve diagnostic assays and to develop new antimicrobial agents for treatment of disease. Our understanding of S. aureus MGEs and the molecules they encode has played an important role toward these ends and has provided detailed insight into the evolution of antimicrobial resistance mechanisms and virulence.
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Affiliation(s)
- Natalia Malachowa
- Laboratory of Human Bacterial Pathogenesis, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 903 South 4th Street, Hamilton, MT 59840 USA
| | - Frank R. DeLeo
- Laboratory of Human Bacterial Pathogenesis, Rocky Mountain Laboratories, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 903 South 4th Street, Hamilton, MT 59840 USA
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192
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Doyle M, Feuerbaum EA, Fox KR, Hinds J, Thurston DE, Taylor PW. Response of Staphylococcus aureus to subinhibitory concentrations of a sequence-selective, DNA minor groove cross-linking pyrrolobenzodiazepine dimer. J Antimicrob Chemother 2009; 64:949-59. [PMID: 19744983 PMCID: PMC2764867 DOI: 10.1093/jac/dkp325] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
OBJECTIVES ELB-21 is a pyrrolo[2,1-c][1,4]benzodiazepine dimer with potent antistaphylococcal activity; it binds covalently to guanine residues on opposing strands of duplex DNA, interfering with regulatory proteins and transcription elongation in a sequence-selective manner. Transcriptional and proteomic alterations induced by exposure of Staphylococcus aureus clinical isolate EMRSA-16 to ELB-21 were determined in order to define more precisely the bactericidal mechanism of the drug. METHODS DNase I footprinting was used to identify high-affinity DNA binding sites. Microarrays and gel electrophoresis were used to assess the ELB-21-induced phenotype. RESULTS High-affinity interstrand binding sites in which guanine residues were separated by 4 bp, and also some intrastrand cross-linking sites of variable length were identified. Exposure of EMRSA-16 to 0.015 mg/L ELB-21 elicited a 2-fold or greater up-regulation of 168 genes in logarithmic phase and 181 genes in stationary phase; the majority of genes affected were associated with resident prophages Sa2 and Sa3, pathogenicity island SaPI4 and DNA damage repair. ELB-21 induced a marked increase in the number of viable phage particles in culture supernatants. The expression of only a limited number of genes showed a >50% reduction. Sixteen extracellular and four intracellular proteins were differentially expressed during logarithmic and stationary phases, including RecA, proteins associated with staphylococcal pathogenesis (IsaA, CspA), cell division and wall synthesis. CONCLUSIONS ELB-21 kills S. aureus by forming multiple interstrand and intrastrand DNA cross-links, resulting in induction of the DNA damage response, derepression of resident prophages and modulation of a limited number of genes involved with cell wall synthesis.
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Affiliation(s)
- Marie Doyle
- School of Pharmacy, University of London, London WC1N 1AX UK
| | | | - Keith R. Fox
- School of Biological Sciences, University of Southampton, Southampton SO16 7PX, UK
| | - Jason Hinds
- Division of Cellular and Molecular Medicine, St. George’s, University of London, London SW17 0RE, UK
| | | | - Peter W. Taylor
- School of Pharmacy, University of London, London WC1N 1AX UK
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193
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Dwyer DJ, Kohanski MA, Collins JJ. Role of reactive oxygen species in antibiotic action and resistance. Curr Opin Microbiol 2009; 12:482-9. [PMID: 19647477 PMCID: PMC2761529 DOI: 10.1016/j.mib.2009.06.018] [Citation(s) in RCA: 313] [Impact Index Per Article: 20.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2009] [Revised: 06/26/2009] [Accepted: 06/30/2009] [Indexed: 12/21/2022]
Abstract
The alarming spread of bacterial strains exhibiting resistance to current antibiotic therapies necessitates that we elucidate the specific genetic and biochemical responses underlying drug-mediated cell killing, so as to increase the efficacy of available treatments and develop new antibacterials. Recent research aimed at identifying such cellular contributions has revealed that antibiotics induce changes in metabolism that promote the formation of reactive oxygen species, which play a role in cell death. Here we discuss the relationship between drug-induced oxidative stress, the SOS response and their potential combined contribution to resistance development. Additionally, we describe ways in which these responses are being taken advantage to combat bacterial infections and arrest the rise of resistant strains.
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Affiliation(s)
- Daniel J Dwyer
- Howard Hughes Medical Institute, Department of Biomedical Engineering, Center for BioDynamics and Center for Advanced Biotechnology, Boston University, 44 Cummington Street, Boston, MA 02215, USA.
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194
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Wirtz C, Witte W, Wolz C, Goerke C. Transcription of the phage-encoded Panton-Valentine leukocidin of Staphylococcus aureus is dependent on the phage life-cycle and on the host background. MICROBIOLOGY-SGM 2009; 155:3491-3499. [PMID: 19661179 DOI: 10.1099/mic.0.032466-0] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Panton-Valentine leukocidin (PVL) is a pore-forming, bi-component toxin secreted by Staphylococcus aureus strains epidemiologically associated with diseases such as necrotizing pneumonia and skin and soft-tissue infections. Here we demonstrate that transcription of the phage-encoded PVL (encoded in the luk-PV operon) is dependent on two major determinants: the phage life-cycle and the host chromosomal background. Mitomycin C induction of PVL-encoding prophages from different community-acquired MRSA strains led to an increase in the amount of luk-PV mRNA as a result of read-through transcription from latent phage promoters and an increase in phage copy numbers. Failing prophage excision was reflected in a constant expression of luk-PV as in the case of strain USA300, suggesting that phi Sa2USA300 is a replication-defective prophage. Additionally, we could show that luk-PV transcription is influenced by the S. aureus global virulence regulators agr and sae. We found a strong impact of the host background on prophage induction and replication when analysing PVL phages in different S. aureus strains. For example phage phi Sa2mw was greatly induced by mitomycin C in its native host MW2 and in strain Newman but to a considerably lesser extent in strains 8325-4, RN6390 and ISP479c. This discrepancy was not linked to the SOS response of the bacteria since recA transcription did not vary between the strains. These results suggest a fine tuning between certain phages and their host, with major impact on the expression of phage-encoded virulence genes.
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Affiliation(s)
- Christiane Wirtz
- Institut für Medizinische Mikrobiologie und Hygiene, Universitätsklinikum Tübingen, Elfriede-Aulhorn-Str. 6, 72076 Tübingen, Germany
| | - Wolfgang Witte
- Robert-Koch-Institut Wernigerode, Burgstr. 37, 38855 Wernigerode, Germany
| | - Christiane Wolz
- Institut für Medizinische Mikrobiologie und Hygiene, Universitätsklinikum Tübingen, Elfriede-Aulhorn-Str. 6, 72076 Tübingen, Germany
| | - Christiane Goerke
- Institut für Medizinische Mikrobiologie und Hygiene, Universitätsklinikum Tübingen, Elfriede-Aulhorn-Str. 6, 72076 Tübingen, Germany
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195
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Santos SB, Carvalho CM, Sillankorva S, Nicolau A, Ferreira EC, Azeredo J. The use of antibiotics to improve phage detection and enumeration by the double-layer agar technique. BMC Microbiol 2009; 9:148. [PMID: 19627589 PMCID: PMC2728735 DOI: 10.1186/1471-2180-9-148] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2009] [Accepted: 07/23/2009] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND The Double-Layer Agar (DLA) technique is extensively used in phage research to enumerate and identify phages and to isolate mutants and new phages. Many phages form large and well-defined plaques that are easily observed so that they can be enumerated when plated by the DLA technique. However, some give rise to small and turbid plaques that are very difficult to detect and count. To overcome these problems, some authors have suggested the use of dyes to improve the contrast between the plaques and the turbid host lawns. It has been reported that some antibiotics stimulate bacteria to produce phages, resulting in an increase in final titer. Thus, antibiotics might contribute to increasing plaque size in solid media. RESULTS Antibiotics with different mechanisms of action were tested for their ability to enhance plaque morphology without suppressing phage development. Some antibiotics increased the phage plaque surface by up to 50-fold. CONCLUSION This work presents a modification of the DLA technique that can be used routinely in the laboratory, leading to a more accurate enumeration of phages that would be difficult or even impossible otherwise.
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Affiliation(s)
- Sílvio B Santos
- Institute for Biotechnology and Bioengineering, Centre of Biological Engineering, Universidade do Minho, Campus de Gualtar, 4700-057 Braga, Portugal
| | - Carla M Carvalho
- Institute for Biotechnology and Bioengineering, Centre of Biological Engineering, Universidade do Minho, Campus de Gualtar, 4700-057 Braga, Portugal
| | - Sanna Sillankorva
- Institute for Biotechnology and Bioengineering, Centre of Biological Engineering, Universidade do Minho, Campus de Gualtar, 4700-057 Braga, Portugal
| | - Ana Nicolau
- Institute for Biotechnology and Bioengineering, Centre of Biological Engineering, Universidade do Minho, Campus de Gualtar, 4700-057 Braga, Portugal
| | - Eugénio C Ferreira
- Institute for Biotechnology and Bioengineering, Centre of Biological Engineering, Universidade do Minho, Campus de Gualtar, 4700-057 Braga, Portugal
| | - Joana Azeredo
- Institute for Biotechnology and Bioengineering, Centre of Biological Engineering, Universidade do Minho, Campus de Gualtar, 4700-057 Braga, Portugal
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196
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Abstract
Investigations of antibiotic resistance from an environmental prospective shed new light on a problem that was traditionally confined to a subset of clinically relevant antibiotic-resistant bacterial pathogens. It is clear that the environmental microbiota, even in apparently antibiotic-free environments, possess an enormous number and diversity of antibiotic resistance genes, some of which are very similar to the genes circulating in pathogenic microbiota. It is difficult to explain the role of antibiotics and antibiotic resistance in natural environments from an anthropocentric point of view, which is focused on clinical aspects such as the efficiency of antibiotics in clearing infections and pathogens that are resistant to antibiotic treatment. A broader overview of the role of antibiotics and antibiotic resistance in nature from the evolutionary and ecological prospective suggests that antibiotics have evolved as another way of intra- and inter-domain communication in various ecosystems. This signalling by non-clinical concentrations of antibiotics in the environment results in adaptive phenotypic and genotypic responses of microbiota and other members of the community. Understanding the complex picture of evolution and ecology of antibiotics and antibiotic resistance may help to understand the processes leading to the emergence and dissemination of antibiotic resistance and also help to control it, at least in relation to the newer antibiotics now entering clinical practice.
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Affiliation(s)
- Rustam I Aminov
- University of Aberdeen, Rowett Institute of Nutrition and Health, Greenburn Road, Aberdeen AB21 9SB, UK.
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197
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Cuirolo A, Plata K, Rosato AE. Development of homogeneous expression of resistance in methicillin-resistant Staphylococcus aureus clinical strains is functionally associated with a beta-lactam-mediated SOS response. J Antimicrob Chemother 2009; 64:37-45. [PMID: 19457930 DOI: 10.1093/jac/dkp164] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
OBJECTIVES One of the main characteristics of methicillin-resistant Staphylococcus aureus (MRSA) from both hospitals and community is their heterogeneous expression of resistance. Recently, we reported new heterogeneous MRSA isolates phenotypically susceptible to oxacillin despite being mecA positive. These low-level mecA-mediated resistance MRSA strains are very heterogeneous in expression (HeR) and are likely to be clinically relevant since exposure of such isolates to beta-lactams can result in high-level homotypic resistance (HoR). We hypothesized that HeR to HoR selection in these clinically relevant strains may be determined by the pre-existence of a hypermutable population that favours its selection in the presence of oxacillin. METHODS Using established procedures, SA13011 HeR to HoR selection was performed by using subinhibitory concentrations of oxacillin and examined for mutability. Real-time RT-PCR and transcriptional profiling by DNA microarray were used to compare gene expression between both populations and related genetically modified SA13011 strain. RESULTS We found that HeR/HoR selection by oxacillin was associated with increased mutation rate and oxacillin-mediated SOS response. We determined increased expression of both mecA and SOS response lexA/recA regulators. Mutational inactivation of lexA repressor resulted in a significant decrease in both mutation rate and oxacillin resistance in the HoR cells. Complementation of the lexA mutant strain restored oxacillin resistance to the high levels observed in the corresponding HoR wild-type strain. CONCLUSIONS The present results support the notion that SOS response is mechanistically involved in generating mutations that, in addition to mecA induction, allow the selection of a highly oxacillin-resistant population.
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Affiliation(s)
- Arabela Cuirolo
- Department of Internal Medicine, Division of Infectious Diseases, Virginia Commonwealth University, Richmond, VA 23298, USA
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198
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Kelly B, Vespermann A, Bolton D. The role of horizontal gene transfer in the evolution of selected foodborne bacterial pathogens. Food Chem Toxicol 2009; 47:951-68. [DOI: 10.1016/j.fct.2008.02.006] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2007] [Revised: 02/04/2008] [Accepted: 02/06/2008] [Indexed: 10/22/2022]
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199
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Horizontal gene transfer of virulence determinants in selected bacterial foodborne pathogens. Food Chem Toxicol 2009; 47:969-77. [DOI: 10.1016/j.fct.2008.02.007] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2007] [Revised: 02/07/2008] [Accepted: 02/07/2008] [Indexed: 11/19/2022]
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200
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Rolain JM, François P, Hernandez D, Bittar F, Richet H, Fournous G, Mattenberger Y, Bosdure E, Stremler N, Dubus JC, Sarles J, Reynaud-Gaubert M, Boniface S, Schrenzel J, Raoult D. Genomic analysis of an emerging multiresistant Staphylococcus aureus strain rapidly spreading in cystic fibrosis patients revealed the presence of an antibiotic inducible bacteriophage. Biol Direct 2009; 4:1. [PMID: 19144117 PMCID: PMC2629466 DOI: 10.1186/1745-6150-4-1] [Citation(s) in RCA: 66] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2009] [Accepted: 01/13/2009] [Indexed: 02/08/2023] Open
Abstract
Background Staphylococcus aureus is a major human pathogen responsible for a variety of nosocomial and community-acquired infections. Recent reports show that the prevalence of Methicillin-Resistant S. aureus (MRSA) infections in cystic fibrosis (CF) patients is increasing. In 2006 in Marseille, France, we have detected an atypical MRSA strain with a specific antibiotic susceptibility profile and a unique growth phenotype. Because of the clinical importance of the spread of such strain among CF patients we decided to sequence the genome of one representative isolate (strain CF-Marseille) to compare this to the published genome sequences. We also conducted a retrospective epidemiological analysis on all S. aureus isolated from 2002 to 2007 in CF patients from our institution. Results CF-Marseille is multidrug resistant, has a hetero-Glycopeptide-Intermediate resistance S. aureus phenotype, grows on Cepacia agar with intense orange pigmentation and has a thickened cell wall. Phylogenetic analyses using Complete Genome Hybridization and Multi Locus VNTR Assay showed that CF-Marseille was closely related to strain Mu50, representing vancomycin-resistant S. aureus. Analysis of CF-Marseille shows a similar core genome to that of previously sequenced MRSA strains but with a different genomic organization due to the presence of specific mobile genetic elements i.e. a new SCCmec type IV mosaic cassette that has integrated the pUB110 plasmid, and a new phage closely related to phiETA3. Moreover this phage could be seen by electron microscopy when mobilized with several antibiotics commonly used in CF patients including, tobramycin, ciprofloxacin, cotrimoxazole, or imipenem. Phylogenetic analysis of phenotypically similar h-GISA in our study also suggests that CF patients are colonized by polyclonal populations of MRSA that represents an incredible reservoir for lateral gene transfer. Conclusion In conclusion, we demonstrated the emergence and spreading of a new isolate of MRSA in CF patients in Marseille, France, that has probably been selected in the airways by antibiotic pressure. Antibiotic-mediated phage induction may result in high-frequency transfer and the unintended consequence of promoting the spread of virulence and/or antibiotic resistance determinants. The emergence of well-adapted MRSA is worrying in such population chronically colonized and receiving many antibiotics and represents a model for emergence of uncontrollable super bugs in a specific niche. Reviewers This article was reviewed by Eric Bapteste, Pierre Pontarotti, and Igor Zhulin. For the full reviews, please go to the Reviewers' comments section.
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Affiliation(s)
- Jean-Marc Rolain
- URMITE CNRS-IRD UMR 6236, Faculté de Médecine et de Pharmacie, Université de la Méditerranée, 27 Boulevard Jean Moulin, 13385 Marseille Cedex 05, France.
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