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Sun J, Deng Z, Yan A. Bacterial multidrug efflux pumps: mechanisms, physiology and pharmacological exploitations. Biochem Biophys Res Commun 2014; 453:254-67. [PMID: 24878531 DOI: 10.1016/j.bbrc.2014.05.090] [Citation(s) in RCA: 432] [Impact Index Per Article: 43.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2014] [Accepted: 05/20/2014] [Indexed: 01/11/2023]
Abstract
Multidrug resistance (MDR) refers to the capability of bacterial pathogens to withstand lethal doses of structurally diverse drugs which are capable of eradicating non-resistant strains. MDR has been identified as a major threat to the public health of human being by the World Health Organization (WHO). Among the four general mechanisms that cause antibiotic resistance including target alteration, drug inactivation, decreased permeability and increased efflux, drug extrusion by the multidrug efflux pumps serves as an important mechanism of MDR. Efflux pumps not only can expel a broad range of antibiotics owing to their poly-substrate specificity, but also drive the acquisition of additional resistance mechanisms by lowering intracellular antibiotic concentration and promoting mutation accumulation. Over-expression of multidrug efflux pumps have been increasingly found to be associated with clinically relevant drug resistance. On the other hand, accumulating evidence has suggested that efflux pumps also have physiological functions in bacteria and their expression is subject tight regulation in response to various of environmental and physiological signals. A comprehensive understanding of the mechanisms of drug extrusion, and regulation and physiological functions of efflux pumps is essential for the development of anti-resistance interventions. In this review, we summarize the development of these research areas in the recent decades and present the pharmacological exploitation of efflux pump inhibitors as a promising anti-drug resistance intervention.
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Affiliation(s)
- Jingjing Sun
- School of Biological Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong Special Administrative Region
| | - Ziqing Deng
- School of Biological Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong Special Administrative Region
| | - Aixin Yan
- School of Biological Sciences, The University of Hong Kong, Pokfulam Road, Hong Kong Special Administrative Region.
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202
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Gomes F, Teixeira P, Oliveira R. Mini-review: Staphylococcus epidermidis as the most frequent cause of nosocomial infections: old and new fighting strategies. BIOFOULING 2014; 30:131-141. [PMID: 24283376 DOI: 10.1080/08927014.2013.848858] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/02/2023]
Abstract
Staphylococcus epidermidis is nowadays regarded as the most frequent cause of nosocomial infections and indwelling medical device-associated infections. One of the features that contributes to the success of this microorganism and which is elemental to the onset of pathogenesis is its ability to form biofilms. Cells in this mode of growth are inherently more resistant to antimicrobials. Seeking to treat staphylococcal-related infections and to prevent their side effects, such as the significant morbidity and health care costs, many efforts are being made to develop of new and effective antistaphylococcal drugs. Indeed, due to its frequency and extreme resistance to treatment, staphylococcal-associated infections represent a serious burden for the public health system. This review will provide an overview of some conventional and emerging anti-biofilm approaches in the management of medical device-associated infections related to this important nosocomial pathogen.
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Affiliation(s)
- F Gomes
- a Centre of Biological Engineering, IBB - Institute for Biotechnology and Bioengineering, University of Minho , Braga , Portugal
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203
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Mardanova AM, Bogomol’naya LM, Romanova YD, Sharipova MR. Efflux systems in Serratia marcescens. Microbiology (Reading) 2014. [DOI: 10.1134/s0026261714010093] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
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204
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Elucidating the genetic basis of crystalline biofilm formation in Proteus mirabilis. Infect Immun 2014; 82:1616-26. [PMID: 24470471 DOI: 10.1128/iai.01652-13] [Citation(s) in RCA: 37] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
Proteus mirabilis forms extensive crystalline biofilms on urethral catheters that occlude urine flow and frequently complicate the management of long-term-catheterized patients. Here, using random transposon mutagenesis in conjunction with in vitro models of the catheterized urinary tract, we elucidate the mechanisms underpinning the formation of crystalline biofilms by P. mirabilis. Mutants identified as defective in blockage of urethral catheters had disruptions in genes involved in nitrogen metabolism and efflux systems but were unaffected in general growth, survival in bladder model systems, or the ability to elevate urinary pH. Imaging of biofilms directly on catheter surfaces, along with quantification of levels of encrustation and biomass, confirmed that the mutants were attenuated specifically in the ability to form crystalline biofilms compared with that of the wild type. However, the biofilm-deficient phenotype of these mutants was not due to deficiencies in attachment to catheter biomaterials, and defects in later stages of biofilm development were indicated. For one blocking-deficient mutant, the disrupted gene (encoding a putative multidrug efflux pump) was also found to be associated with susceptibility to fosfomycin, and loss of this system or general inhibition of efflux pumps increased sensitivity to this antibiotic. Furthermore, homologues of this system were found to be widely distributed among other common pathogens of the catheterized urinary tract. Overall, our findings provide fundamental new insight into crystalline biofilm formation by P. mirabilis, including the link between biofilm formation and antibiotic resistance in this organism, and indicate a potential role for efflux pump inhibitors in the treatment or prevention of P. mirabilis crystalline biofilms.
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205
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Characterization of a novel pyranopyridine inhibitor of the AcrAB efflux pump of Escherichia coli. Antimicrob Agents Chemother 2013; 58:722-33. [PMID: 24247144 DOI: 10.1128/aac.01866-13] [Citation(s) in RCA: 135] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Members of the resistance-nodulation-division (RND) family of efflux pumps, such as AcrAB-TolC of Escherichia coli, play major roles in multidrug resistance (MDR) in Gram-negative bacteria. A strategy for combating MDR is to develop efflux pump inhibitors (EPIs) for use in combination with an antibacterial agent. Here, we describe MBX2319, a novel pyranopyridine EPI with potent activity against RND efflux pumps of the Enterobacteriaceae. MBX2319 decreased the MICs of ciprofloxacin (CIP), levofloxacin, and piperacillin versus E. coli AB1157 by 2-, 4-, and 8-fold, respectively, but did not exhibit antibacterial activity alone and was not active against AcrAB-TolC-deficient strains. MBX2319 (3.13 μM) in combination with 0.016 μg/ml CIP (minimally bactericidal) decreased the viability (CFU/ml) of E. coli AB1157 by 10,000-fold after 4 h of exposure, in comparison with 0.016 μg/ml CIP alone. In contrast, phenyl-arginine-β-naphthylamide (PAβN), a known EPI, did not increase the bactericidal activity of 0.016 μg/ml CIP at concentrations as high as 100 μM. MBX2319 increased intracellular accumulation of the fluorescent dye Hoechst 33342 in wild-type but not AcrAB-TolC-deficient strains and did not perturb the transmembrane proton gradient. MBX2319 was broadly active against Enterobacteriaceae species and Pseudomonas aeruginosa. MBX2319 is a potent EPI with possible utility as an adjunctive therapeutic agent for the treatment of infections caused by Gram-negative pathogens.
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206
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Baugh S, Phillips CR, Ekanayaka AS, Piddock LJV, Webber MA. Inhibition of multidrug efflux as a strategy to prevent biofilm formation. J Antimicrob Chemother 2013; 69:673-81. [DOI: 10.1093/jac/dkt420] [Citation(s) in RCA: 109] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
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207
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Applying insights from biofilm biology to drug development — can a new approach be developed? Nat Rev Drug Discov 2013; 12:791-808. [DOI: 10.1038/nrd4000] [Citation(s) in RCA: 348] [Impact Index Per Article: 31.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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208
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Schindler BD, Jacinto P, Kaatz GW. Inhibition of drug efflux pumps in Staphylococcus aureus: current status of potentiating existing antibiotics. Future Microbiol 2013; 8:491-507. [PMID: 23534361 DOI: 10.2217/fmb.13.16] [Citation(s) in RCA: 71] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The emergence of multidrug-resistant Staphylococcus aureus coupled with a declining output of new antibiotic treatment options from the pharmaceutical industry is a growing worldwide healthcare problem. Multidrug efflux pumps are known to play a role in antibiotic and biocide resistance in S. aureus. These membrane transporters are capable of extruding drugs and other structurally unrelated compounds, hence decreasing intracellular concentration and increasing survival. Coadministration of efflux pump inhibitors (EPIs) with antibiotics that are pump substrates could increase intracellular drug levels, thus bringing renewed efficacy to existing antistaphylococcal agents. Numerous EPIs have been identified or synthesized over the past two decades; these include existing pharmacologic drugs, naturally occurring compounds, and synthetic derivatives thereof. This review describes the current progress in EPI development for use against S. aureus.
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Affiliation(s)
- Bryan D Schindler
- John D Dingell Veterans Affairs Medical Center, Wayne State University, Detroit, MI 48201, USA
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209
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Sabatini S, Gosetto F, Iraci N, Barreca ML, Massari S, Sancineto L, Manfroni G, Tabarrini O, Dimovska M, Kaatz GW, Cecchetti V. Re-evolution of the 2-Phenylquinolines: Ligand-Based Design, Synthesis, and Biological Evaluation of a Potent New Class of Staphylococcus aureus NorA Efflux Pump Inhibitors to Combat Antimicrobial Resistance. J Med Chem 2013; 56:4975-89. [DOI: 10.1021/jm400262a] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Stefano Sabatini
- Dipartimento di Chimica e Tecnologia
del Farmaco, Università degli Studi di Perugia, 06123 Perugia, Italy
| | - Francesca Gosetto
- Dipartimento di Chimica e Tecnologia
del Farmaco, Università degli Studi di Perugia, 06123 Perugia, Italy
| | - Nunzio Iraci
- Dipartimento di Chimica e Tecnologia
del Farmaco, Università degli Studi di Perugia, 06123 Perugia, Italy
| | - Maria Letizia Barreca
- Dipartimento di Chimica e Tecnologia
del Farmaco, Università degli Studi di Perugia, 06123 Perugia, Italy
| | - Serena Massari
- Dipartimento di Chimica e Tecnologia
del Farmaco, Università degli Studi di Perugia, 06123 Perugia, Italy
| | - Luca Sancineto
- Dipartimento di Chimica e Tecnologia
del Farmaco, Università degli Studi di Perugia, 06123 Perugia, Italy
| | - Giuseppe Manfroni
- Dipartimento di Chimica e Tecnologia
del Farmaco, Università degli Studi di Perugia, 06123 Perugia, Italy
| | - Oriana Tabarrini
- Dipartimento di Chimica e Tecnologia
del Farmaco, Università degli Studi di Perugia, 06123 Perugia, Italy
| | - Mirjana Dimovska
- John D. Dingell Department of
Veterans Affairs Medical Center and the Department of Internal Medicine,
Division of Infectious Diseases, School of Medicine, Wayne State University, Detroit, Michigan 48201, United
States
| | - Glenn W. Kaatz
- John D. Dingell Department of
Veterans Affairs Medical Center and the Department of Internal Medicine,
Division of Infectious Diseases, School of Medicine, Wayne State University, Detroit, Michigan 48201, United
States
| | - Violetta Cecchetti
- Dipartimento di Chimica e Tecnologia
del Farmaco, Università degli Studi di Perugia, 06123 Perugia, Italy
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210
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Cugini C, Klepac-Ceraj V, Rackaityte E, Riggs JE, Davey ME. Porphyromonas gingivalis: keeping the pathos out of the biont. J Oral Microbiol 2013; 5:19804. [PMID: 23565326 PMCID: PMC3617648 DOI: 10.3402/jom.v5i0.19804] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2012] [Revised: 02/18/2013] [Accepted: 02/18/2013] [Indexed: 01/21/2023] Open
Abstract
The primary goal of the human microbiome initiative has been to increase our understanding of the structure and function of our indigenous microbiota and their effects on human health and predisposition to disease. Because of its clinical importance and accessibility for in vivo study, the oral biofilm is one of the best-understood microbial communities associated with the human body. Studies have shown that there is a succession of select microbial interactions that directs the maturation of a defined community structure, generating the formation of dental plaque. Although the initiating factors that lead to disease development are not clearly defined, in many individuals there is a fundamental shift from a health-associated biofilm community to one that is pathogenic in nature and a central player in the pathogenic potential of this community is the presence of Porphyromonas gingivalis. This anaerobic bacterium is a natural member of the oral microbiome, yet it can become highly destructive (termed pathobiont) and proliferate to high cell numbers in periodontal lesions, which is attributed to its arsenal of specialized virulence factors. Hence, this organism is regarded as a primary etiologic agent of periodontal disease progression. In this review, we summarize some of the latest information regarding what is known about its role in periodontitis, including pathogenic potential as well as ecological and nutritional parameters that may shift this commensal to a virulent state. We also discuss parallels between the development of pathogenic biofilms and the human cellular communities that lead to cancer, specifically we frame our viewpoint in the context of 'wounds that fail to heal'.
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Affiliation(s)
- Carla Cugini
- Department of Microbiology, The Forsyth Institute, Cambridge, MA, USA ; Department of Oral Medicine Infection and Immunity, Harvard School of Dental Medicine, Boston, MA, USA
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211
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Soto SM. Role of efflux pumps in the antibiotic resistance of bacteria embedded in a biofilm. Virulence 2013; 4:223-9. [PMID: 23380871 PMCID: PMC3711980 DOI: 10.4161/viru.23724] [Citation(s) in RCA: 254] [Impact Index Per Article: 23.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2012] [Revised: 01/22/2013] [Accepted: 01/23/2013] [Indexed: 02/08/2023] Open
Abstract
Biofilms are complex microbial associations anchored to abiotic or biotic surfaces, embedded in extracellular matrix produced by the biofilms themselves where they interact with each other and the environment. One of the main properties of biofilms is their capacity to be more resistant to antimicrobial agents than planktonic cells. Efflux pumps have been reported as one of the mechanisms responsible for the antimicrobial resistance in biofilm structures. Evidence of the role of efflux pump in biofilm resistance has been found in several microorganisms such as Pseudomonas aeruginosa, Escherichia coli and Candida albicans. However, in spite of the studies on the importance of efflux pumps in biofilm growth and about their relevance in antimicrobial resistance forming biofilm, the exact role of these efflux systems has not been determined as yet.
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Affiliation(s)
- Sara M Soto
- Barcelona Centre for International Health Research (CRESIB, Hospital Clinic-University of Barcelona), Barcelona, Spain.
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212
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Fernando DM, Kumar A. Resistance-Nodulation-Division Multidrug Efflux Pumps in Gram-Negative Bacteria: Role in Virulence. Antibiotics (Basel) 2013; 2:163-81. [PMID: 27029297 PMCID: PMC4790303 DOI: 10.3390/antibiotics2010163] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/28/2012] [Revised: 03/05/2013] [Accepted: 03/11/2013] [Indexed: 01/13/2023] Open
Abstract
Resistance-Nodulation-Division (RND) efflux pumps are one of the most important determinants of multidrug resistance (MDR) in Gram-negative bacteria. With an ever increasing number of Gram-negative clinical isolates exhibiting MDR phenotypes as a result of the activity of RND pumps, it is clear that the design of novel effective clinical strategies against such pathogens must be grounded in a better understanding of these pumps, including their physiological roles. To this end, recent evidence suggests that RND pumps play an important role in the virulence of Gram-negative pathogens. In this review, we discuss the important role RND efflux pumps play in different facets of virulence including colonization, evasion of host defense mechanisms, and biofilm formation. These studies provide key insights that may ultimately be applied towards strategies used in the design of effective therapeutics against MDR Gram negative bacterial pathogens.
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Affiliation(s)
- Dinesh M Fernando
- Antimicrobial Resistance Research Group (ARRG), Applied Bioscience Program, Faculties of Health Sciences and Science, University of Ontario Institute of Technology, 2000 Simcoe Street N, Oshawa, ON L1H 7K4, Canada.
| | - Ayush Kumar
- Antimicrobial Resistance Research Group (ARRG), Applied Bioscience Program, Faculties of Health Sciences and Science, University of Ontario Institute of Technology, 2000 Simcoe Street N, Oshawa, ON L1H 7K4, Canada.
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213
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Chen YT, Peng HL, Shia WC, Hsu FR, Ken CF, Tsao YM, Chen CH, Liu CE, Hsieh MF, Chen HC, Tang CY, Ku TH. Whole-genome sequencing and identification of Morganella morganii KT pathogenicity-related genes. BMC Genomics 2012; 13 Suppl 7:S4. [PMID: 23282187 PMCID: PMC3521468 DOI: 10.1186/1471-2164-13-s7-s4] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND The opportunistic enterobacterium, Morganella morganii, which can cause bacteraemia, is the ninth most prevalent cause of clinical infections in patients at Changhua Christian Hospital, Taiwan. The KT strain of M. morganii was isolated during postoperative care of a cancer patient with a gallbladder stone who developed sepsis caused by bacteraemia. M. morganii is sometimes encountered in nosocomial settings and has been causally linked to catheter-associated bacteriuria, complex infections of the urinary and/or hepatobiliary tracts, wound infection, and septicaemia. M. morganii infection is associated with a high mortality rate, although most patients respond well to appropriate antibiotic therapy. To obtain insights into the genome biology of M. morganii and the mechanisms underlying its pathogenicity, we used Illumina technology to sequence the genome of the KT strain and compared its sequence with the genome sequences of related bacteria. RESULTS The 3,826,919-bp sequence contained in 58 contigs has a GC content of 51.15% and includes 3,565 protein-coding sequences, 72 tRNA genes, and 10 rRNA genes. The pathogenicity-related genes encode determinants of drug resistance, fimbrial adhesins, an IgA protease, haemolysins, ureases, and insecticidal and apoptotic toxins as well as proteins found in flagellae, the iron acquisition system, a type-3 secretion system (T3SS), and several two-component systems. Comparison with 14 genome sequences from other members of Enterobacteriaceae revealed different degrees of similarity to several systems found in M. morganii. The most striking similarities were found in the IS4 family of transposases, insecticidal toxins, T3SS components, and proteins required for ethanolamine use (eut operon) and cobalamin (vitamin B12) biosynthesis. The eut operon and the gene cluster for cobalamin biosynthesis are not present in the other Proteeae genomes analysed. Moreover, organisation of the 19 genes of the eut operon differs from that found in the other non-Proteeae enterobacterial genomes. CONCLUSIONS This is the first genome sequence of M. morganii, which is a clinically relevant pathogen. Comparative genome analysis revealed several pathogenicity-related genes and novel genes not found in the genomes of other members of Proteeae. Thus, the genome sequence of M. morganii provides important information concerning virulence and determinants of fitness in this pathogen.
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Affiliation(s)
- Yu-Tin Chen
- Department of Computer Science, National Tsing Hua University, 101, Section 2, Kuang-Fu Rd., Hsinchu, Taiwan
| | - Hwei-Ling Peng
- Department of Biological Science and Technology, National Chiao Tung University, 1001, University Road, Hsinchu, Taiwan
| | - Wei-Chung Shia
- Cancer Research Center, Changhua Christian Hospital, 135, Nanhsiao St., Changhua, Taiwan
| | - Fang-Rong Hsu
- Master's Program in Biomedical Informatics and Biomedical Engineering, Feng Chia University, 100 Wenhwa Rd., Taichung, Taiwan
- Department of Information Engineering and Computer Sciences, Feng Chia University, 100 Wenhwa Rd., Taichung, Taiwan
| | - Chuian-Fu Ken
- Institute of Biotechnology, National Changhua University of Education, 2 Shi-Da Rd., Changhua, Taiwan
| | - Yu-Ming Tsao
- Department of Anesthesiology, Changhua Christian Hospital, 135, Nanhsiao St., Changhua, Taiwan
| | - Chang-Hua Chen
- The Division of Infectious Diseases, Department of Internal Medicine, Changhua Christian Hospital, 135, Nanhsiao St., Changhua, Taiwan
| | - Chun-Eng Liu
- The Division of Infectious Diseases, Department of Internal Medicine, Changhua Christian Hospital, 135, Nanhsiao St., Changhua, Taiwan
| | - Ming-Feng Hsieh
- Department of Computer Science, National Tsing Hua University, 101, Section 2, Kuang-Fu Rd., Hsinchu, Taiwan
| | - Huang-Chi Chen
- Division of Critical Care Medicine, Department of Internal Medicine, Changhua Christian Hospital, 135, Nanhsiao St., Changhua, Taiwan
| | - Chuan-Yi Tang
- Department of Computer Science, National Tsing Hua University, 101, Section 2, Kuang-Fu Rd., Hsinchu, Taiwan
- Department of Computer Science, Providence University, 200, Chung-Chi Rd., Taichung, Taiwan
| | - Tien-Hsiung Ku
- Department of Anesthesiology, Changhua Christian Hospital, 135, Nanhsiao St., Changhua, Taiwan
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216
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Ciofu O, Mandsberg LF, Wang H, Høiby N. Phenotypes selected during chronic lung infection in cystic fibrosis patients: implications for the treatment ofPseudomonas aeruginosabiofilm infections. ACTA ACUST UNITED AC 2012; 65:215-25. [DOI: 10.1111/j.1574-695x.2012.00983.x] [Citation(s) in RCA: 67] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2011] [Revised: 04/23/2012] [Accepted: 04/24/2012] [Indexed: 12/18/2022]
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217
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Baugh S, Ekanayaka AS, Piddock LJV, Webber MA. Loss of or inhibition of all multidrug resistance efflux pumps of Salmonella enterica serovar Typhimurium results in impaired ability to form a biofilm. J Antimicrob Chemother 2012; 67:2409-17. [PMID: 22733653 DOI: 10.1093/jac/dks228] [Citation(s) in RCA: 129] [Impact Index Per Article: 10.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
OBJECTIVES To investigate the contribution of multidrug efflux pump systems of Salmonella enterica serovar Typhimurium to the formation of a competent biofilm. METHODS Biofilm formation by a wild-type strain and 10 efflux mutant strains was quantified using crystal violet biofilm assays and visualized using scanning electron microscopy. Curli expression was investigated qualitatively and quantitatively by measuring binding of the dye Congo red to polymerized curli and by comparative RT-PCR. RESULTS All efflux mutants of Salmonella Typhimurium were compromised in their ability to form biofilms. Scanning electron microscopy images showed that the mutants were able to adhere to a surface but were unable to form a complex three-dimensional biofilm. Congo red assays demonstrated an inability of the efflux mutants to produce curli, a proteinaceous filament present on the cell surface and an essential component of the Salmonella biofilm extracellular matrix. Mutants expressed significantly less csgB or csgD than wild-type. Chemical inactivation of efflux in wild-type Salmonella Typhimurium with the efflux inhibitors (EIs) phenyl-arginine-β-naphthylamide, carbonyl cyanide m-chlorophenylhydrazone and chlorpromazine also repressed biofilm formation. CONCLUSIONS Our data demonstrates a link between all efflux systems of Salmonella Typhimurium and biofilm formation. Loss of functional efflux gives rise to a lack of curli expression. Biofilm formation was also inhibited by addition of a variety of EIs with differing mechanisms of action, suggesting a novel role for EIs as anti-biofilm compounds.
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Affiliation(s)
- Stephanie Baugh
- School of Immunity and Infection, College of Medical and Dental Sciences, University of Birmingham, Edgbaston, Birmingham B15 2TT, UK
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218
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Schweizer HP. Understanding efflux in Gram-negative bacteria: opportunities for drug discovery. Expert Opin Drug Discov 2012; 7:633-42. [PMID: 22607346 DOI: 10.1517/17460441.2012.688949] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
Abstract
INTRODUCTION Bacteria evolved an arsenal of mechanisms to deal with toxic compounds and metabolic stresses, including antimicrobial agents. Efflux pumps are major players in the multidrug resistance of Gram-negative bacteria and pose major hurdles in the drug discovery process. However, recent advances in our understanding of efflux in these bacteria provide opportunities and assets for drug discovery. AREAS COVERED This review provides an overview of drug efflux in Gram-negative bacteria and its role in antimicrobial resistance, stress responses and other biological processes such as biofilm formation, and virulence. The discussion includes comments on the significance of synergy between a low-permeability outer membrane and efflux, notably the role of porins and lipopolysaccharide. The author then summarizes efforts aimed at inhibiting efflux pumps as a means to extend the utility of clinically useful antibiotics. This includes highlights of identification and characterization of small molecule efflux pump inhibitors (EPIs) from natural and synthetic sources, as well as novel strategies such as gene silencing and inhibitory antibodies. EXPERT OPINION Options for treating infections caused by multidrug-resistant bacteria are limited. Given the attractiveness of the therapeutic potential of efflux pump inhibition, further studies exploring novel strategies to interfere with efflux pump expression and function are warranted. This includes rational EPI design facilitated by pump structure information, exploitation of genetically defined efflux-proficient and efflux-compromised strain panels and non-traditional approaches such as pump inhibition by gene silencing, antibodies and perhaps even phage.
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Affiliation(s)
- Herbert P Schweizer
- Colorado State University, IDRC at Foothills Campus, Department of Microbiology, Immunology and Pathology, Fort Collins, CO 80523-0922, USA.
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219
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The response regulator RcsB activates expression of Mat fimbriae in meningitic Escherichia coli. J Bacteriol 2012; 194:3475-85. [PMID: 22522901 DOI: 10.1128/jb.06596-11] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The common colonization factor of Escherichia coli, the Mat (also termed ECP) fimbria, functions to advance biofilm formation on inert surfaces as well as bacterial adherence to epithelial cells and subsequent colonization. We used global mini-Tn5 transposon mutagenesis to identify novel regulators of biofilm formation by the meningitic E. coli isolate IHE 3034. Of the 4,418 transformants, we found 17 that were impaired in biofilm formation. Most of these mutants were affected in lipopolysaccharide synthesis and were reduced in growth but not in Mat fimbria expression. In contrast, two mutants grew well but did not express Mat fimbria. The insertions in these two mutants were located at different sites of the rcsB gene, which encodes a DNA-binding response regulator of the Rcs response regulon. The mutations abrogated temperature-dependent biofilm formation by IHE 3034, and the phenotype correlated with loss of mat expression. The defect in biofilm formation in the rcsB mutant was reversed upon complementation with rcsB as well as by overexpression of structural mat genes but not by overexpression of the fimbria-specific activator gene matA. Monitoring of the mat operon promoter activity with chromosomal reporter fusions showed that the RcsB protein and an RcsAB box in the mat regulatory region, but not RcsC, RcsD, AckA, and Pta, are essential for initiation of mat transcription. Gel retardation assays showed that RcsB specifically binds to the mat promoter DNA, which enables its function in promoting biofilm formation by E. coli.
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220
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Tegos GP, Haynes M, Strouse JJ, Khan MMT, Bologa CG, Oprea TI, Sklar LA. Microbial efflux pump inhibition: tactics and strategies. Curr Pharm Des 2011; 17:1291-302. [PMID: 21470111 DOI: 10.2174/138161211795703726] [Citation(s) in RCA: 91] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2011] [Accepted: 03/21/2011] [Indexed: 11/22/2022]
Abstract
Traditional antimicrobials are increasingly suffering from the emergence of multidrug resistance among pathogenic microorganisms. To overcome these deficiencies, a range of novel approaches to control microbial infections are under investigation as potential alternative treatments. Multidrug efflux is a key target of these efforts. Efflux mechanisms are broadly recognized as major components of resistance to many classes of chemotherapeutic agents as well as antimicrobials. Efflux occurs due to the activity of membrane transporter proteins widely known as Multidrug Efflux Systems (MES). They are implicated in a variety of physiological roles other than efflux and identifying natural substrates and inhibitors is an active and expanding research discipline. One plausible alternative is the combination of conventional antimicrobial agents/antibiotics with small molecules that block MES known as multidrug efflux pump inhibitors (EPIs). An array of approaches in academic and industrial research settings, varying from high-throughput screening (HTS) ventures to bioassay guided purification and determination, have yielded a number of promising EPIs in a series of pathogenic systems. This synergistic discovery platform has been exploited in translational directions beyond the potentiation of conventional antimicrobial treatments. This venture attempts to highlight different tactical elements of this platform, identifying the need for highly informative and comprehensive EPI-discovery strategies. Advances in assay development genomics, proteomics as well as the accumulation of bioactivity and structural information regarding MES facilitates the basis for a new discovery era. This platform is expanding drastically. A combination of chemogenomics and chemoinformatics approaches will integrate data mining with virtual and physical HTS ventures and populate the chemical-biological interface with a plethora of novel chemotypes. This comprehensive step will expedite the preclinical development of lead EPIs.
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Affiliation(s)
- George P Tegos
- Center for Molecular Discovery, University of New Mexico, Albuquerque, NM 87131, USA.
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221
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Evidence of significant synergism between antibiotics and the antipsychotic, antimicrobial drug flupenthixol. Eur J Clin Microbiol Infect Dis 2011; 31:1243-50. [PMID: 21997771 DOI: 10.1007/s10096-011-1435-3] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2011] [Accepted: 09/20/2011] [Indexed: 10/16/2022]
Abstract
Previously, the antipsychotic, non-antibiotic compound flupenthixol dihydrochloride (Fp) was shown to exhibit distinct in vitro antibacterial activity against Gram-positive and Gram-negative bacteria and to significantly protect Swiss albino mice challenged with a known mouse virulent salmonella. The present study was designed to ascertain whether this drug could efficiently augment the action of an antibiotic or a non-antibiotic when tested in combination. A total of 12 bacterial strains belonging to various genera were selected for this study and were sensitive to the antibiotics penicillin (Pc), ampicillin, chloramphenicol, tetracycline, streptomycin, gentamicin, erythromycin, ciprofloxacin, and to the non-antibiotics methdilazine, triflupromazine, promethazine, and Fp. Pronounced and statistically significant synergism (p < 0.01) was observed when Fp was combined with Pc following the disc diffusion assay system. With the help of the checkerboard method, the fractional inhibitory concentration (FIC) index of this pair was found to be 0.375, confirming synergism. This pair of Fp+ Pc was then subjected to in vivo experiments in mice challenged with Salmonella enterica serovar Typhimurium NCTC 74. Statistical analysis of the mouse protection test suggested that this combination was highly synergistic (p < 0.001, Chi-squared analysis). Fp also revealed augmentation of its antimicrobial property when combined with streptomycin, gentamicin, ciprofloxacin, and the non-antibiotic methdilazine. The results of this study may provide alternatives for the therapy of problematic infections such as those associated with Salmonella spp.
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222
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Role of Efflux Pump Inhibitors on the Antibiofilm Efficacy of Calcium Hydroxide, Chitosan Nanoparticles, and Light-activated Disinfection. J Endod 2011; 37:1422-6. [DOI: 10.1016/j.joen.2011.06.017] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2011] [Revised: 06/10/2011] [Accepted: 06/23/2011] [Indexed: 01/08/2023]
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223
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Bridier A, Briandet R, Thomas V, Dubois-Brissonnet F. Resistance of bacterial biofilms to disinfectants: a review. BIOFOULING 2011; 27:1017-32. [PMID: 22011093 DOI: 10.1080/08927014.2011.626899] [Citation(s) in RCA: 525] [Impact Index Per Article: 40.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/10/2023]
Abstract
A biofilm can be defined as a community of microorganisms adhering to a surface and surrounded by a complex matrix of extrapolymeric substances. It is now generally accepted that the biofilm growth mode induces microbial resistance to disinfection that can lead to substantial economic and health concerns. Although the precise origin of such resistance remains unclear, different studies have shown that it is a multifactorial process involving the spatial organization of the biofilm. This review will discuss the mechanisms identified as playing a role in biofilm resistance to disinfectants, as well as novel anti-biofilm strategies that have recently been explored.
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Affiliation(s)
- A Bridier
- AgroParisTech, UMR MICALIS, F-91300 Massy, France
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224
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Matsumura K, Furukawa S, Ogihara H, Morinaga Y. Roles of multidrug efflux pumps on the biofilm formation of Escherichia coli K-12. Biocontrol Sci 2011; 16:69-72. [PMID: 21719992 DOI: 10.4265/bio.16.69] [Citation(s) in RCA: 81] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022]
Abstract
We genetically analyzed the roles of multidrug efflux pumps on the biofilm formation of Escherichia coli K-12 BW25113. We used 22 mutants missing various genes related to the multidrug efflux pumps and found that the biofilm formation of emrD, emrE, emrK, acrD, acre and mdtE-deleted mutants was extremely decreased. These results indicate that some multidrug efflux pumps significantly contribute to the biofilm formation of E. coli.
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Affiliation(s)
- Kayo Matsumura
- Department of Food Bioscience and Biotechnology, College of Bioresource Science, Nihon University, Kameino, Fujisawa, Japan.
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225
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Sabatini S, Gosetto F, Manfroni G, Tabarrini O, Kaatz GW, Patel D, Cecchetti V. Evolution from a Natural Flavones Nucleus to Obtain 2-(4-Propoxyphenyl)quinoline Derivatives As Potent Inhibitors of the S. aureus NorA Efflux Pump. J Med Chem 2011; 54:5722-36. [DOI: 10.1021/jm200370y] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Affiliation(s)
- Stefano Sabatini
- Dipartimento di Chimica e Tecnologia del Farmaco, Università degli Studi di Perugia, 06123 Perugia, Italy
| | - Francesca Gosetto
- Dipartimento di Chimica e Tecnologia del Farmaco, Università degli Studi di Perugia, 06123 Perugia, Italy
| | - Giuseppe Manfroni
- Dipartimento di Chimica e Tecnologia del Farmaco, Università degli Studi di Perugia, 06123 Perugia, Italy
| | - Oriana Tabarrini
- Dipartimento di Chimica e Tecnologia del Farmaco, Università degli Studi di Perugia, 06123 Perugia, Italy
| | - Glenn W. Kaatz
- Department of Internal Medicine, Division of Infectious Diseases, School of Medicine, Wayne State University, and the John D. Dingell Department of Veteran Affairs Medical Center, Detroit, Michigan 48201, United States
| | - Diixa Patel
- Department of Internal Medicine, Division of Infectious Diseases, School of Medicine, Wayne State University, and the John D. Dingell Department of Veteran Affairs Medical Center, Detroit, Michigan 48201, United States
| | - Violetta Cecchetti
- Dipartimento di Chimica e Tecnologia del Farmaco, Università degli Studi di Perugia, 06123 Perugia, Italy
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226
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227
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Bordi C, de Bentzmann S. Hacking into bacterial biofilms: a new therapeutic challenge. Ann Intensive Care 2011; 1:19. [PMID: 21906350 PMCID: PMC3224501 DOI: 10.1186/2110-5820-1-19] [Citation(s) in RCA: 83] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2011] [Accepted: 06/13/2011] [Indexed: 02/07/2023] Open
Abstract
Microbiologists have extensively worked during the past decade on a particular phase of the bacterial cell cycle known as biofilm, in which single-celled individuals gather together to form a sedentary but dynamic community within a complex structure, displaying spatial and functional heterogeneity. In response to the perception of environmental signals by sensing systems, appropriate responses are triggered, leading to biofilm formation. This process involves various molecular systems that enable bacteria to identify appropriate surfaces on which to anchor themselves, to stick to those surfaces and to each other, to construct multicellular communities several hundreds of micrometers thick, and to detach from the community. The biofilm microbial community is a unique, highly competitive, and crowded environment facilitating microevolutionary processes and horizontal gene transfer between distantly related microorganisms. It is governed by social rules, based on the production and use of "public" goods, with actors and recipients. Biofilms constitute a unique shield against external aggressions, including drug treatment and immune reactions. Biofilm-associated infections in humans have therefore generated major problems for the diagnosis and treatment of diseases. Improvements in our understanding of biofilms have led to innovative research designed to interfere with this process.
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Affiliation(s)
- Christophe Bordi
- Laboratoire d'Ingénierie des Systèmes Macromoléculaires, UPR9027 CNRS - Aix Marseille Université, Institut de Microbiologie de la Méditerranée, 31 Chemin Joseph Aiguier, 13402 Marseille, France.
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228
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Hancock V, Witsø IL, Klemm P. Biofilm formation as a function of adhesin, growth medium, substratum and strain type. Int J Med Microbiol 2011; 301:570-6. [PMID: 21646046 DOI: 10.1016/j.ijmm.2011.04.018] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2011] [Revised: 04/05/2011] [Accepted: 04/20/2011] [Indexed: 12/21/2022] Open
Abstract
Biofilm formation is involved in the majority of bacterial infections. Comparing six Escherichia coli and Klebsiella pneumoniae isolates revealed significant differences in biofilm formation depending on the growth medium. Fimbriae are known to be involved in biofilm formation, and type 1, F1C and P fimbriae were seen to influence biofilm formation significantly different depending on strain background, growth media and aeration as well as surface material. Altogether, this report clearly demonstrates that biofilm formation of a given strain is highly dependent on experimental design and that specific mechanisms involved in biofilm formation such as fimbrial expression only play a role under certain environmental conditions. This study underscores the importance of careful selection of experimental conditions when investigating bacterial biofilm formation and to take great precaution/care when comparing results from different biofilm studies.
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Affiliation(s)
- Viktoria Hancock
- Microbial Adhesion Group, DTU Food, Technical University of Denmark, Lyngby, Denmark.
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229
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Abstract
Bile acid resistance by Lactococcus lactis depends on the ABC-type multidrug transporter LmrCD. Upon deletion of the lmrCD genes, cells can reacquire bile acid resistance upon prolonged exposure to cholate, yielding the ΔlmrCD(r) strain. The resistance mechanism in this strain is non-transporter based. Instead, cells show a high tendency to flocculate, suggesting cell surface alterations. Contact angle measurements demonstrate that the ΔlmrCD(r) cells are equipped with an increased cell surface hydrophilicity compared to those of the parental and wild-type strains, while the surface hydrophilicity is reduced in the presence of cholate. ΔlmrCD(r) cells are poor in biofilm formation on a hydrophobic polystyrene surface, but in the presence of subinhibitory concentrations of cholate, biofilm formation is strongly stimulated. Biofilm cells show an enhanced extracellular polymeric substance production and are highly resistant to bile acids. These data suggest that non-transporter-based cholate resistance in L. lactis is due to alterations in the cell surface that stimulate cells to form resistant biofilms.
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230
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Li L, Li Z, Guo N, Jin J, Du R, Liang J, Wu X, Wang X, Liu M, Jin Q, Yu L. Synergistic activity of 1-(1-naphthylmethyl)-piperazine with ciprofloxacin against clinically resistant Staphylococcus aureus, as determined by different methods. Lett Appl Microbiol 2011; 52:372-8. [DOI: 10.1111/j.1472-765x.2011.03010.x] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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231
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A transcriptional regulator and ABC transporters link stress tolerance, (p)ppGpp, and genetic competence in Streptococcus mutans. J Bacteriol 2010; 193:862-74. [PMID: 21148727 DOI: 10.1128/jb.01257-10] [Citation(s) in RCA: 53] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Streptococcus mutans, a primary agent of dental caries, has three (p)ppGpp synthases: RelA, which is required for a mupirocin-induced stringent response; RelP, which produces (p)ppGpp during exponential growth and is regulated by the RelRS two-component system; and RelQ. Transcription of relPRS and a gene cluster (SMu0835 to SMu0837) located immediately upstream was activated in cells grown with aeration and during a stringent response, respectively. Bioinformatic analysis predicted that SMu0836 and SMu0837 encode ABC exporters, which we designated rcrPQ (rel competence-related) genes, respectively. SMu0835 (rcrR) encodes a MarR family transcriptional regulator. Reverse transcriptase PCR (RT-PCR) and quantitative RT-PCR analysis showed that RcrR functions as an autogenous negative regulator of the expression of the rcrRPQ operon. A mutant in which a polar insertion replaced the SMu836 gene (Δ836polar) grew more slowly and had final yields that were lower than those of the wild-type strain. Likewise, the Δ836polar strain had an impaired capacity to form biofilms, grew poorly at pH 5.5, and was more sensitive to oxidative stressors. Optimal expression of rcrPQ required RelP and vice versa. Replacement of rcrR with a nonpolar antibiotic resistance marker (Δ835np), which leads to overexpression of rcrPQ, yielded a strain that was not transformable with exogenous DNA. Transcriptional analysis revealed that the expression of comYA and comX was dramatically altered in the Δ835np and Δ836polar mutants. Collectively, the data support the suggestion that the rcrRPQ gene products play a critical role in physiologic homeostasis and stress tolerance by linking (p)ppGpp metabolism, acid and oxidative stress tolerance, and genetic competence.
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232
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Kishen A, Upadya M, Tegos GP, Hamblin MR. Efflux pump inhibitor potentiates antimicrobial photodynamic inactivation of Enterococcus faecalis biofilm. Photochem Photobiol 2010; 86:1343-9. [PMID: 20860692 DOI: 10.1111/j.1751-1097.2010.00792.x] [Citation(s) in RCA: 78] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Microbial biofilm architecture contains numerous protective features, including extracellular polymeric material that render biofilms impermeable to conventional antimicrobial agents. This study evaluated the efficacy of antimicrobial photodynamic inactivation (aPDI) of Enterococcus faecalis biofilms. The ability of a cationic, phenothiazinium photosensitizer, methylene blue (MB) and an anionic, xanthene photosensitizer, rose bengal (RB) to inactivate biofilms of E. faecalis (OG1RF and FA 2-2) and disrupt the biofilm structure was evaluated. Bacterial cells were tested as planktonic suspensions, intact biofilms and biofilm-derived suspensions obtained by the mechanical disruption of biofilms. The role of a specific microbial efflux pump inhibitor (EPI), verapamil hydrochloride in the MB-mediated aPDI of E. faecalis biofilms was also investigated. The results showed that E. faecalis biofilms exhibited significantly higher resistance to aPDI when compared with E. faecalis in suspension (P < 0.001). aPDI with cationic MB produced superior inactivation of E. faecalis strains in a biofilm along with significant destruction of biofilm structure when compared with anionic RB (P < 0.05). The ability to inactivate biofilm bacteria was further enhanced when the EPI was used with MB (P < 0.001). These experiments demonstrated the advantage of a cationic phenothiazinium photosensitizer combined with an EPI to inactivate biofilm bacteria and disrupt biofilm structure.
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Affiliation(s)
- Anil Kishen
- Endodontics, Faculty of Dentistry, University of Toronto, Toronto, Canada
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233
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Hancock V, Dahl M, Vejborg RM, Klemm P. Dietary plant components ellagic acid and tannic acid inhibit Escherichia coli biofilm formation. J Med Microbiol 2009; 59:496-498. [PMID: 19959627 DOI: 10.1099/jmm.0.013680-0] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Affiliation(s)
- Viktoria Hancock
- Microbial Genomics Group, Center for Biological Sequence Analysis, Departmentof Systems Biology, Technical University of Denmark, Lyngby, Denmark
| | - Malin Dahl
- Microbial Genomics Group, Center for Biological Sequence Analysis, Departmentof Systems Biology, Technical University of Denmark, Lyngby, Denmark
| | - Rebecca Munk Vejborg
- Microbial Genomics Group, Center for Biological Sequence Analysis, Departmentof Systems Biology, Technical University of Denmark, Lyngby, Denmark
| | - Per Klemm
- Microbial Genomics Group, Center for Biological Sequence Analysis, Departmentof Systems Biology, Technical University of Denmark, Lyngby, Denmark
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234
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Glover WA, Yang Y, Zhang Y. Insights into the molecular basis of L-form formation and survival in Escherichia coli. PLoS One 2009; 4:e7316. [PMID: 19806199 PMCID: PMC2752164 DOI: 10.1371/journal.pone.0007316] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2009] [Accepted: 09/02/2009] [Indexed: 11/30/2022] Open
Abstract
L-forms have been shown to occur among many species of bacteria and are suspected to be involved in persistent infections. Since their discovery in 1935, numerous studies characterizing L-form morphology, growth, and pathogenic potential have been conducted. However, the molecular mechanisms underlying the formation and survival of L-forms remain unknown. Using unstable L-form colonies of Escherichia coli as a model, we performed genome-wide transcriptome analysis and screened a deletion mutant library to study the molecular mechanisms involved in formation and survival of L-forms. Microarray analysis of L-form versus classical colonies revealed many up-regulated genes of unknown function as well as multiple over-expressed stress pathways shared in common with persister cells and biofilms. Mutant screens identified three groups of mutants which displayed varying degrees of defects in L-form colony formation. Group 1 mutants, which showed the strongest defect in L-form colony formation, belonged to pathways involved in cell envelope stress, DNA repair, iron homeostasis, outer membrane biogenesis, and drug efflux/ABC transporters. Four (Group 1) mutants, rcsB, a positive response regulator of colanic acid capsule synthesis, ruvA, a recombinational junction binding protein, fur, a ferric uptake regulator and smpA a small membrane lipoprotein were selected for complementation. Complementation of the mutants using a high-copy overexpression vector failed, while utilization of a low-copy inducible vector successfully restored L-form formation. This work represents the first systematic genetic evaluation of genes and pathways involved in the formation and survival of unstable L-form bacteria. Our findings provide new insights into the molecular mechanisms underlying L-form formation and survival and have implications for understanding the emergence of antibiotic resistance, bacterial persistence and latent infections and designing novel drugs and vaccines.
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Affiliation(s)
- William A. Glover
- Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Yanqin Yang
- Bioinformatics Core, The Wilmer Eye Institute, School of Medicine, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Ying Zhang
- Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland, United States of America
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235
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Induction of multidrug resistance mechanism in Escherichia coli biofilms by interplay between tetracycline and ampicillin resistance genes. Antimicrob Agents Chemother 2009; 53:4628-39. [PMID: 19721076 DOI: 10.1128/aac.00454-09] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Biofilms gain resistance to various antimicrobial agents, and the presence of antibiotic resistance genes is thought to contribute to a biofilm-mediated antibiotic resistance. Here we showed the interplay between the tetracycline resistance efflux pump TetA(C) and the ampicillin resistance gene (bla(TEM-1)) in biofilms of Escherichia coli harboring pBR322 in the presence of the mixture of ampicillin and tetracycline. E. coli in the biofilms could obtain the high-level resistance to ampicillin, tetracycline, penicillin, erythromycin, and chloramphenicol during biofilm development and maturation as a result of the interplay between the marker genes on the plasmids, the increase of plasmid copy number, and consequently the induction of the efflux systems on the bacterial chromosome, especially the EmrY/K and EvgA/S pumps. In addition, we characterized the overexpression of the TetA(C) pump that contributed to osmotic stress response and was involved in the induction of capsular colanic acid production, promoting formation of mature biofilms. However, this investigated phenomenon was highly dependent on the addition of the subinhibitory concentrations of antibiotic mixture, and the biofilm resistance behavior was limited to aminoglycoside antibiotics. Thus, marker genes on plasmids played an important role in both resistance of biofilm cells to antibiotics and in formation of mature biofilms, as they could trigger specific chromosomal resistance mechanisms to confer a high-level resistance during biofilm formation.
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