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Ho CH, Chen CW, Su PY. Membranome-based identification of amino acid substitution in Haemophilus influenzae multidrug efflux pump HmrM for reduced chloramphenicol susceptibility. Arch Microbiol 2024; 206:298. [PMID: 38860999 DOI: 10.1007/s00203-024-04025-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2024] [Revised: 05/21/2024] [Accepted: 05/30/2024] [Indexed: 06/12/2024]
Abstract
A decreased chloramphenicol susceptibility in Haemophilus influenzae is commonly caused by the activity of chloramphenicol acetyltransferases (CATs). However, the involvement of membrane proteins in chloramphenicol susceptibility in H. influenzae remains unclear. In this study, chloramphenicol susceptibility testing, whole-genome sequencing, and analyses of membrane-related genes were performed in 51 H. influenzae isolates. Functional complementation assays and structure-based protein analyses were conducted to assess the effect of proteins with sequence substitutions on the minimum inhibitory concentration (MIC) of chloramphenicol in CAT-negative H. influenzae isolates. Six isolates were resistant to chloramphenicol and positive for type A-2 CATs. Of these isolates, A3256 had a similar level of CAT activity but a higher chloramphenicol MIC relative to the other resistant isolates; it also had 163 specific variations in 58 membrane genes. Regarding the CAT-negative isolates, logistic regression and receiver operator characteristic curve analyses revealed that 48T > G (Asn16Lys), 85 C > T (Leu29Phe), and 88 C > A (Leu30Ile) in HI_0898 (emrA), and 86T > G (Phe29Cys) and 141T > A (Ser47Arg) in HI_1177 (artM) were associated with enhanced chloramphenicol susceptibility, whereas 997G > A (Val333Ile) in HI_1612 (hmrM) was associated with reduced chloramphenicol susceptibility. Furthermore, the chloramphenicol MIC was lower in the CAT-negative isolates with EmrA-Leu29Phe/Leu30Ile or ArtM-Ser47Arg substitution and higher in those with HmrM-Val333Ile substitution, relative to their counterparts. The Val333Ile substitution was associated with enhanced HmrM protein stability and flexibility and increased chloramphenicol MICs in CAT-negative H. influenzae isolates. In conclusion, the substitution in H. influenzae multidrug efflux pump HmrM associated with reduced chloramphenicol susceptibility was characterised.
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Affiliation(s)
- Cheng-Hsun Ho
- Department of Medical Laboratory Science, College of Medical Science and Technology, I-Shou University, No.8, Yida Road, Jiaosu Village, Yanchao District, Kaohsiung, 82445, Taiwan.
| | - Chi-Wei Chen
- Graduate Degree Program of Smart Healthcare & Bioinformatics, College of Medical Science and Technology, I-Shou University, Kaohsiung, Taiwan
- Department of Biomedical Engineering, College of Medical Science and Technology, I-Shou University, Kaohsiung, Taiwan
| | - Pei-Yi Su
- Department of Laboratory Medicine, E-DA Hospital, Kaohsiung, Taiwan
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2
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Ho CH, Chen CJ, Hsieh CY, Su PY. Amino acid substitutions in the region between RpoB clusters II and III on rifampin susceptibility in Haemophilus influenzae. Eur J Clin Microbiol Infect Dis 2023; 42:1499-1509. [PMID: 37906391 DOI: 10.1007/s10096-023-04689-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2023] [Accepted: 10/18/2023] [Indexed: 11/02/2023]
Abstract
BACKGROUND Rifampin is a potent chemoprophylactic antibiotic for Haemophilus influenzae infection, and the resistance rate in H. influenzae is low. In this study, we assessed rifampin resistance-related genetic variations in H. influenzae. METHODS Rifampin susceptibility testing and whole-genome sequencing were performed in 51 H. influenzae isolates. Variations associated with rifampin resistance were identified using Fisher's exact tests. Functional assays were performed to evaluate the effect of RpoB substitutions on rifampin susceptibility. RESULTS Using the genome of the Rd KW20 H. influenzae strain as the reference, we detected 40 genetic variations in rpoB, which resulted in 39 deduced amino acid substitutions among the isolates. Isolate A0586 was resistant to rifampin, with a minimum inhibitory concentration (MIC) = 8 μg/mL. Phylogenetic analyses revealed that the RpoB sequence of isolate A0586 was distinct from other isolates. Five substitutions, including H526N located in cluster I and L623F, R628C, L645F, and L672F in the region between clusters II and III, were unique to isolate A0586. In two rifampin-susceptible H. influenzae isolates, RpoB-H526N alone and in combination with RpoB-L672F increased the MICs of rifampin to 4 and 8 μg/mL, respectively. RpoB-L672F did not affect cell growth and transcription in H. influenzae isolates. No amino acid substitutions in the AcrAB-TolC efflux pump or outer membrane proteins were found to be associated with rifampin resistance in H. influenzae. CONCLUSIONS Our findings indicate that L672F substitution in the region between RpoB clusters II and III has an aggravating effect on rifampin resistance in H. influenzae.
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Affiliation(s)
- Cheng-Hsun Ho
- Department of Medical Laboratory Science, College of Medical Science and Technology, I-Shou University, Kaohsiung, Taiwan.
| | - Chuan-Jung Chen
- Department of Medical Laboratory Science, College of Medical Science and Technology, I-Shou University, Kaohsiung, Taiwan
| | - Chia-Yun Hsieh
- Department of Medical Laboratory Science, College of Medical Science and Technology, I-Shou University, Kaohsiung, Taiwan
| | - Pei-Yi Su
- Department of Laboratory Medicine, E-DA Hospital, Kaohsiung, Taiwan
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3
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Abstract
Vibrio cholerae is a Gram-negative bacterium that causes the enteric disease cholera. V. cholerae colonization of the human intestine is dependent on the expression of both virulence genes and environmental adaptation genes involved in antimicrobial resistance. The expression of virulence genes, including the genes encoding for the main virulence factors cholera toxin (CT) and the toxin coregulated pilus (TCP), are coordinately regulated by the ToxR regulon. Tripartite transport systems belonging to the ATP binding cassette, major facilitator, and Resistance-Nodulation-Division families are critical for V. cholerae pathogenesis. Transport systems belonging to these families contribute to myriad phenotypes including protein secretion, antimicrobial resistance and virulence. TolC plays a central role in bacterial physiology by functioning as the outer membrane pore protein for tripartite transport systems. Consistent with this, V. cholerae tolC was previously found to be required for MARTX toxin secretion and antimicrobial resistance. Herein we investigated the contribution of TolC to V. cholerae virulence. We documented that tolC was required for CT and TCP production in O1 El Tor V. cholerae. This phenotype was linked to repression of the critical ToxR regulon transcription factor aphA. Decreased aphA transcription correlated with increased expression of the LysR-family transcription factor leuO. Deletion of leuO restored aphA expression, and CT and TCP production, in a tolC mutant. The collective results document that tolC is required for ToxR regulon expression and further suggest that tolC may participate in a efflux-dependent feedback circuit to regulate virulence gene expression.
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de Nies L, Lopes S, Busi SB, Galata V, Heintz-Buschart A, Laczny CC, May P, Wilmes P. PathoFact: a pipeline for the prediction of virulence factors and antimicrobial resistance genes in metagenomic data. MICROBIOME 2021; 9:49. [PMID: 33597026 PMCID: PMC7890817 DOI: 10.1186/s40168-020-00993-9] [Citation(s) in RCA: 67] [Impact Index Per Article: 22.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/21/2020] [Accepted: 12/29/2020] [Indexed: 05/24/2023]
Abstract
BACKGROUND Pathogenic microorganisms cause disease by invading, colonizing, and damaging their host. Virulence factors including bacterial toxins contribute to pathogenicity. Additionally, antimicrobial resistance genes allow pathogens to evade otherwise curative treatments. To understand causal relationships between microbiome compositions, functioning, and disease, it is essential to identify virulence factors and antimicrobial resistance genes in situ. At present, there is a clear lack of computational approaches to simultaneously identify these factors in metagenomic datasets. RESULTS Here, we present PathoFact, a tool for the contextualized prediction of virulence factors, bacterial toxins, and antimicrobial resistance genes with high accuracy (0.921, 0.832 and 0.979, respectively) and specificity (0.957, 0.989 and 0.994). We evaluate the performance of PathoFact on simulated metagenomic datasets and perform a comparison to two other general workflows for the analysis of metagenomic data. PathoFact outperforms all existing workflows in predicting virulence factors and toxin genes. It performs comparably to one pipeline regarding the prediction of antimicrobial resistance while outperforming the others. We further demonstrate the performance of PathoFact on three publicly available case-control metagenomic datasets representing an actual infection as well as chronic diseases in which either pathogenic potential or bacterial toxins are hypothesized to play a role. In each case, we identify virulence factors and AMR genes which differentiated between the case and control groups, thereby revealing novel gene associations with the studied diseases. CONCLUSION PathoFact is an easy-to-use, modular, and reproducible pipeline for the identification of virulence factors, bacterial toxins, and antimicrobial resistance genes in metagenomic data. Additionally, our tool combines the prediction of these pathogenicity factors with the identification of mobile genetic elements. This provides further depth to the analysis by considering the genomic context of the pertinent genes. Furthermore, PathoFact's modules for virulence factors, toxins, and antimicrobial resistance genes can be applied independently, thereby making it a flexible and versatile tool. PathoFact, its models, and databases are freely available at https://pathofact.lcsb.uni.lu . Video abstract.
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Affiliation(s)
- Laura de Nies
- Systems Ecology Research Group, Luxembourg Centre for Systems Biomedicine, Esch-sur-Alzette, Luxembourg
| | - Sara Lopes
- Systems Ecology Research Group, Luxembourg Centre for Systems Biomedicine, Esch-sur-Alzette, Luxembourg
| | - Susheel Bhanu Busi
- Systems Ecology Research Group, Luxembourg Centre for Systems Biomedicine, Esch-sur-Alzette, Luxembourg
| | - Valentina Galata
- Systems Ecology Research Group, Luxembourg Centre for Systems Biomedicine, Esch-sur-Alzette, Luxembourg
| | - Anna Heintz-Buschart
- Systems Ecology Research Group, Luxembourg Centre for Systems Biomedicine, Esch-sur-Alzette, Luxembourg
- Metagenomics Support Unit, German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Leipzig, Germany
- Department of Soil Ecology, Helmholtz Centre for Environmental Research GmbH-UFZ, Halle (Saale), Germany
| | - Cedric Christian Laczny
- Systems Ecology Research Group, Luxembourg Centre for Systems Biomedicine, Esch-sur-Alzette, Luxembourg
| | - Patrick May
- Bioinformatics Core, Luxembourg Centre for Systems Biomedicine, Esch-sur-Alzette, Luxembourg
| | - Paul Wilmes
- Systems Ecology Research Group, Luxembourg Centre for Systems Biomedicine, Esch-sur-Alzette, Luxembourg.
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Debroy R, Miryala SK, Naha A, Anbarasu A, Ramaiah S. Gene interaction network studies to decipher the multi-drug resistance mechanism in Salmonella enterica serovar Typhi CT18 reveal potential drug targets. Microb Pathog 2020; 142:104096. [PMID: 32097747 DOI: 10.1016/j.micpath.2020.104096] [Citation(s) in RCA: 38] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2020] [Revised: 02/21/2020] [Accepted: 02/21/2020] [Indexed: 01/13/2023]
Abstract
Salmonella enterica subsp. enterica serovar Typhi, a human enteric pathogen causing typhoid fever, developed resistance to multiple antibiotics over the years. The current study was dedicated to understand the multi-drug resistance (MDR) mechanism of S. enterica serovar Typhi CT18 and to identify potential drug targets that could be exploited for new drug discovery. We have employed gene interaction network analysis for 44 genes which had 275 interactions. Clustering analysis resulted in three highly interconnecting clusters (C1-C3). Functional enrichment analysis revealed the presence of drug target alteration and three different multi-drug efflux pumps in the bacteria that were associated with antibiotic resistance. We found seven genes (arnA,B,C,D,E,F,T) conferring resistance to Cationic Anti-Microbial Polypeptide (CAMP) molecules by membrane Lipopolysaccharide (LPS) modification, while macB was observed to be an essential controlling hub of the network and played a crucial role in MacAB-TolC efflux pump. Further, we identified five genes (mdtH, mdtM, mdtG, emrD and mdfA) which were involved in Major Facilitator Superfamily (MFS) efflux system and acrAB contributed towards AcrAB-TolC efflux pump. All three efflux pumps were seen to be highly dependent on tolC gene. The five genes, namely tolC, macB, acrA, acrB and mdfA which were involved in multiple resistance pathways, can act as potential drug targets for successful treatment strategies. Therefore, this study has provided profound insights into the MDR mechanism in S. Typhi CT18. Our results will be useful for experimental biologists to explore new leads for S. enterica.
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Affiliation(s)
- Reetika Debroy
- Medical and Biological Computing Laboratory, School of Bio-Sciences and Technology, Vellore Institute of Technology (VIT), Vellore, 632014, Tamil Nadu, India
| | - Sravan Kumar Miryala
- Medical and Biological Computing Laboratory, School of Bio-Sciences and Technology, Vellore Institute of Technology (VIT), Vellore, 632014, Tamil Nadu, India
| | - Aniket Naha
- Medical and Biological Computing Laboratory, School of Bio-Sciences and Technology, Vellore Institute of Technology (VIT), Vellore, 632014, Tamil Nadu, India
| | - Anand Anbarasu
- Medical and Biological Computing Laboratory, School of Bio-Sciences and Technology, Vellore Institute of Technology (VIT), Vellore, 632014, Tamil Nadu, India
| | - Sudha Ramaiah
- Medical and Biological Computing Laboratory, School of Bio-Sciences and Technology, Vellore Institute of Technology (VIT), Vellore, 632014, Tamil Nadu, India.
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Misawa K, Tarumoto N, Tamura S, Osa M, Hamamoto T, Yuki A, Kouzaki Y, Imai K, Ronald RL, Yamaguchi T, Murakami T, Maesaki S, Suzuki Y, Kawana A, Maeda T. Single nucleotide polymorphisms in genes encoding penicillin-binding proteins in β-lactamase-negative ampicillin-resistant Haemophilus influenzae in Japan. BMC Res Notes 2018; 11:53. [PMID: 29352811 PMCID: PMC5775570 DOI: 10.1186/s13104-018-3169-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/28/2017] [Accepted: 01/12/2018] [Indexed: 01/31/2023] Open
Abstract
Objective β-Lactamase-negative ampicillin-resistant Haemophilus influenzae is a common opportunistic pathogen of hospital- and community-acquired infections, harboring multiple single nucleotide polymorphisms in the ftsI gene, which codes for penicillin-binding protein-3. The objectives of this study were to perform comprehensive genetic analyses of whole regions of the penicillin-binding proteins in H. influenzae and to identify additional single nucleotide polymorphisms related to antibiotic resistance, especially to ampicillin and other cephalosporins. Results In this genome analysis of the ftsI gene in 27 strains of H. influenzae, 10 of 23 (43.5%) specimens of group III genotype β-lactamase-negative ampicillin-resistant H. influenzae were paradoxically classified as ampicillin-sensitive phenotypes. Unfortunately, we could not identify any novel mutations that were significantly associated with ampicillin minimum inhibitory concentrations in other regions of the penicillin-binding proteins, and we reconfirmed that susceptibility to β-lactam antibiotics was mainly defined by previously reported SNPs in the ftsI gene. We should also consider detailed changes in expression that lead to antibiotic resistance in the future because the acquisition of resistance to antimicrobials can be predicted by the expression levels of a small number of genes. Electronic supplementary material The online version of this article (10.1186/s13104-018-3169-0) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Kazuhisa Misawa
- Department of Infectious Diseases and Pulmonary Medicine, National Defense Medical College, Saitama, Japan
| | - Norihito Tarumoto
- Department of Infectious Disease and Infection Control, Saitama Medical University, Saitama, Japan.,Center for Clinical Infectious Diseases and Research, Saitama Medical University, Saitama, Japan
| | - Shinsuke Tamura
- Department of Pediatrics, National Defense Medical College, Saitama, Japan
| | - Morichika Osa
- Department of Infectious Diseases and Pulmonary Medicine, National Defense Medical College, Saitama, Japan
| | - Takaaki Hamamoto
- Department of Laboratory Medicine, National Defense Medical College Hospital, Saitama, Japan
| | - Atsushi Yuki
- Department of Laboratory Medicine, National Defense Medical College Hospital, Saitama, Japan
| | - Yuji Kouzaki
- Department of Infectious Diseases and Pulmonary Medicine, National Defense Medical College, Saitama, Japan
| | - Kazuo Imai
- Department of Infectious Diseases and Pulmonary Medicine, National Defense Medical College, Saitama, Japan
| | - Runtuwene Lucky Ronald
- Department of Computational Biology and Medical Science, Graduate School of Frontier Sciences, The University of Tokyo, Chiba, Japan
| | - Toshiyuki Yamaguchi
- Department of Infectious Disease and Infection Control, Saitama Medical University, Saitama, Japan.,Center for Clinical Infectious Diseases and Research, Saitama Medical University, Saitama, Japan
| | - Takashi Murakami
- Center for Clinical Infectious Diseases and Research, Saitama Medical University, Saitama, Japan.,Department of Microbiology, Saitama Medical University, 38 Morohongo, Moroyama-machi, Iruma-gun, Saitama, 350-0495, Japan
| | - Shigefumi Maesaki
- Department of Infectious Disease and Infection Control, Saitama Medical University, Saitama, Japan.,Center for Clinical Infectious Diseases and Research, Saitama Medical University, Saitama, Japan
| | - Yutaka Suzuki
- Department of Computational Biology and Medical Science, Graduate School of Frontier Sciences, The University of Tokyo, Chiba, Japan
| | - Akihiko Kawana
- Department of Infectious Diseases and Pulmonary Medicine, National Defense Medical College, Saitama, Japan
| | - Takuya Maeda
- Department of Laboratory Medicine, National Defense Medical College Hospital, Saitama, Japan. .,Department of Microbiology, Saitama Medical University, 38 Morohongo, Moroyama-machi, Iruma-gun, Saitama, 350-0495, Japan.
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7
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Yamada T, Wajima T, Nakaminami H, Kobayashi K, Ikoshi H, Noguchi N. The modified Gingyo-san, a Chinese herbal medicine, has direct antibacterial effects against respiratory pathogens. BMC COMPLEMENTARY AND ALTERNATIVE MEDICINE 2016; 16:463. [PMID: 27842538 PMCID: PMC5109643 DOI: 10.1186/s12906-016-1431-3] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 09/21/2016] [Accepted: 10/27/2016] [Indexed: 11/10/2022]
Abstract
BACKGROUND Modified Gingyo-san (MGS) is empirically used to treat various respiratory infections. MGS has been reported to have antiinflammatory and antiviral activities; however, it is not known if it has an antibacterial activity. Therefore, in this study, we aimed to investigate the antimicrobial activity of MGS against respiratory pathogens. METHODS MGS, which is sold as an over-the-counter drug in Japan, was used for the study. Antimicrobial activity was evaluated using the disk diffusion method. Growth inhibitory activity was evaluated by measuring colony-forming units of the pathogens in the presence of MGS. RESULTS MGS inhibited the growth of Bacillus subtilis, Streptococcus pneumoniae, and Streptococcus pyogenes, which are gram-positive bacteria. Although the growth of most gram-negative bacteria was not inhibited by MGS, interestingly, the growth of Haemophilus influenzae was inhibited. MGS did not show any activity against Candida albicans or bacteriophage φX174. CONCLUSIONS In addition to the antiinflammatory and antiviral activities of MGS, which have already been reported, the data obtained from this study indicates that MGS has an antibacterial activity.
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8
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Seyama S, Wajima T, Nakaminami H, Noguchi N. Clarithromycin Resistance Mechanisms of Epidemic β-Lactamase-Nonproducing Ampicillin-Resistant Haemophilus influenzae Strains in Japan. Antimicrob Agents Chemother 2016; 60:3207-10. [PMID: 26953210 PMCID: PMC4862528 DOI: 10.1128/aac.00163-16] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/19/2016] [Accepted: 02/29/2016] [Indexed: 11/20/2022] Open
Abstract
The aim of this study was to clarify the clarithromycin resistance mechanisms of β-lactamase-nonproducing ampicillin-resistant Haemophilus influenzae strains. In all clarithromycin-resistant strains, the transcript level of acrB was significantly elevated, and these strains had a frameshift mutation in acrR Introduction of the acrR mutation into H. influenzae Rd generated a clarithromycin-resistant transformant with the same MIC as the donor strain. Our results indicate that the acrR mutation confers clarithromycin resistance by the increasing the transcription of acrB.
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Affiliation(s)
- Shoji Seyama
- Department of Microbiology, School of Pharmacy, Tokyo University of Pharmacy and Life Sciences, Tokyo, Japan
| | - Takeaki Wajima
- Department of Microbiology, School of Pharmacy, Tokyo University of Pharmacy and Life Sciences, Tokyo, Japan
| | - Hidemasa Nakaminami
- Department of Microbiology, School of Pharmacy, Tokyo University of Pharmacy and Life Sciences, Tokyo, Japan
| | - Norihisa Noguchi
- Department of Microbiology, School of Pharmacy, Tokyo University of Pharmacy and Life Sciences, Tokyo, Japan
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Li XZ, Plésiat P, Nikaido H. The challenge of efflux-mediated antibiotic resistance in Gram-negative bacteria. Clin Microbiol Rev 2015; 28:337-418. [PMID: 25788514 PMCID: PMC4402952 DOI: 10.1128/cmr.00117-14] [Citation(s) in RCA: 924] [Impact Index Per Article: 102.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023] Open
Abstract
The global emergence of multidrug-resistant Gram-negative bacteria is a growing threat to antibiotic therapy. The chromosomally encoded drug efflux mechanisms that are ubiquitous in these bacteria greatly contribute to antibiotic resistance and present a major challenge for antibiotic development. Multidrug pumps, particularly those represented by the clinically relevant AcrAB-TolC and Mex pumps of the resistance-nodulation-division (RND) superfamily, not only mediate intrinsic and acquired multidrug resistance (MDR) but also are involved in other functions, including the bacterial stress response and pathogenicity. Additionally, efflux pumps interact synergistically with other resistance mechanisms (e.g., with the outer membrane permeability barrier) to increase resistance levels. Since the discovery of RND pumps in the early 1990s, remarkable scientific and technological advances have allowed for an in-depth understanding of the structural and biochemical basis, substrate profiles, molecular regulation, and inhibition of MDR pumps. However, the development of clinically useful efflux pump inhibitors and/or new antibiotics that can bypass pump effects continues to be a challenge. Plasmid-borne efflux pump genes (including those for RND pumps) have increasingly been identified. This article highlights the recent progress obtained for organisms of clinical significance, together with methodological considerations for the characterization of MDR pumps.
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Affiliation(s)
- Xian-Zhi Li
- Human Safety Division, Veterinary Drugs Directorate, Health Products and Food Branch, Health Canada, Ottawa, Ontario, Canada
| | - Patrick Plésiat
- Laboratoire de Bactériologie, Faculté de Médecine-Pharmacie, Centre Hospitalier Régional Universitaire, Université de Franche-Comté, Besançon, France
| | - Hiroshi Nikaido
- Department of Molecular and Cell Biology, University of California, Berkeley, California, USA
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10
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Yoshida T, Nasu H, Namba E, Ubukata O, Yamashita M. Discovery of a compound which acts as a bacterial UMP kinase PyrH inhibitor. FEMS Microbiol Lett 2012; 330:121-6. [PMID: 22428584 DOI: 10.1111/j.1574-6968.2012.02546.x] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2012] [Revised: 02/28/2012] [Accepted: 03/01/2012] [Indexed: 11/29/2022] Open
Abstract
PyrH is a member of the UMP kinase family that catalyses the conversion of UMP to UDP, an essential step in the pyrimidine metabolic pathway in a variety of bacteria including those causing community-acquired respiratory tract infections (RTIs). In this study, we have developed a luminescence-based kinase assay of PyrH and evaluated the inhibitory activity of PYRH-1 (sodium {3-[4-tert-butyl-3-(9H-xanthen-9-ylacetylamino)phenyl]-1-cyclohexylmethylpropoxycarbonyloxy}acetate). PYRH-1 inhibits PyrH derived from both Streptococcus pneumoniae and Haemophilus influenzae with IC(50) (concentration of inhibitor giving a 50% decrease in enzyme activity) values of 48 and 75 μM, respectively, whose inhibitory activity against S. pneumoniae PyrH was far higher compared with that of UTP (IC(50) = 710 μM), an allosteric PyrH inhibitor. The molecular interaction analysis by surface plasmon resonance suggested that PYRH-1 directly interacts with S. pneumoniae PyrH at one-to-one molar ratio. Finally, PYRH-1 was shown to have antimicrobial activity against several different bacteria causing RTIs, such as S. pneumoniae, Staphylococcus aureus, H. influenzae (acrA knockout strain), suggesting that PYRH-1 is a prototype chemical compound that can be harnessed as an antimicrobial drug with a novel mode of action by targeting bacterial PyrH.
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Affiliation(s)
- Tatsuhiko Yoshida
- Biological Research Laboratories IV, Daiichi Sankyo Co., Ltd, Tokyo, Japan.
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Zgurskaya HI, Krishnamoorthy G, Ntreh A, Lu S. Mechanism and Function of the Outer Membrane Channel TolC in Multidrug Resistance and Physiology of Enterobacteria. Front Microbiol 2011; 2:189. [PMID: 21954395 PMCID: PMC3174397 DOI: 10.3389/fmicb.2011.00189] [Citation(s) in RCA: 154] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2011] [Accepted: 08/25/2011] [Indexed: 01/18/2023] Open
Abstract
TolC is an archetypal member of the outer membrane efflux protein (OEP) family. These proteins are involved in export of small molecules and toxins across the outer membrane of Gram-negative bacteria. Genomes of some bacteria such as Pseudomonas species contain multiple copies of OEPs. In contrast, enterobacteria contain a single tolC gene, the product of which functions with multiple transporters. Inactivation of tolC has a major impact on enterobacterial physiology and virulence. Recent studies suggest that the role of TolC in physiology of enterobacteria is very broad and affects almost all aspects of cell adaptation to adverse environments. We review the current state of understanding TolC structure and present an integrated view of TolC function in enterobacteria. We propose that seemingly unrelated phenotypes of tolC mutants are linked together by a single most common condition – an oxidative damage to membranes.
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Affiliation(s)
- Helen I Zgurskaya
- Department of Chemistry and Biochemistry, University of Oklahoma Norman, OK, USA
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12
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Fmt bypass in Pseudomonas aeruginosa causes induction of MexXY efflux pump expression. Antimicrob Agents Chemother 2009; 53:5015-21. [PMID: 19786597 DOI: 10.1128/aac.00253-09] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The intrinsic resistance of P. aeruginosa PAO1 to the peptide deformylase inhibitor (PDF-I) LBM415 was mediated by the MexAB-OprM and MexXY-OprM efflux pumps, the latter of which was strongly induced by LBM415. Single-step exposure of PAO1 deleted for mexAB-oprM (therefore lacking both MexAB-OprM and MexXY-OprM functions) to PDF-Is selected for nfxB mutants, which express the MexCD-OprJ efflux pump, indicating that these compounds are also substrates for this pump. Selection of resistant mutants by use of levels of LBM415 greater than that accommodated by efflux yielded two additional groups of mutations, in the methionyl-tRNA(fmet) formyltransferase (fmt) and folD genes. Both mechanisms are known to impose an in vitro growth deficit (also observed here), presumably due to impairment of protein synthesis. We surmised that this inherent impairment of protein synthesis would upregulate expression of mexXY in a fashion similar to upregulation by LBM415 or by ribosome inhibitory compounds. Transcriptional profiling and/or mexX::lux promoter fusion analysis revealed that fmt and folD mutants were strongly upregulated for mexXY and another gene known to be required for upregulation of the pump, PA5471. Complementation of the fmt mutation in trans reversed this constitutive expression. This supports the notion that MexXY has a natural physiological function responding to impairment of ribosome function or protein synthesis and that fmt mutation (Fmt bypass) and folD mutation generate the intracellular mexXY-inducing signal.
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Abstract
Drug efflux pumps play a key role in drug resistance and also serve other functions in bacteria. There has been a growing list of multidrug and drug-specific efflux pumps characterized from bacteria of human, animal, plant and environmental origins. These pumps are mostly encoded on the chromosome, although they can also be plasmid-encoded. A previous article in this journal provided a comprehensive review regarding efflux-mediated drug resistance in bacteria. In the past 5 years, significant progress has been achieved in further understanding of drug resistance-related efflux transporters and this review focuses on the latest studies in this field since 2003. This has been demonstrated in multiple aspects that include but are not limited to: further molecular and biochemical characterization of the known drug efflux pumps and identification of novel drug efflux pumps; structural elucidation of the transport mechanisms of drug transporters; regulatory mechanisms of drug efflux pumps; determining the role of the drug efflux pumps in other functions such as stress responses, virulence and cell communication; and development of efflux pump inhibitors. Overall, the multifaceted implications of drug efflux transporters warrant novel strategies to combat multidrug resistance in bacteria.
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Affiliation(s)
- Xian-Zhi Li
- Human Safety Division, Veterinary Drugs Directorate, Health Products and Food Branch, Health Canada, Ottawa, Ontario K1A OK9, Canada
| | - Hiroshi Nikaido
- Department of Molecular and Cell Biology, University of California, Berkeley, California 94720-3202, USA
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14
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Characterization of TolC efflux pump proteins from Pasteurella multocida. Antimicrob Agents Chemother 2008; 52:4166-71. [PMID: 18725450 DOI: 10.1128/aac.00245-08] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Two TolC homologs, PM0527 and PM1980, were identified for Pasteurella multocida. A pm0527 mutant displayed increased susceptibility to a range of chemicals, including rifampin (512-fold) and acridine orange (128-fold). A pm1980 mutant showed increased susceptibility to rifampin, ceftazidime, and vancomycin.
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15
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Ohkoshi Y, Yokota SI, Sato K, Hayashi T, Matsuda K, Kuwahara O, Akizawa H, Fujii N. Antibiotic susceptibility of Haemophilus influenzae strains isolated from various clinical sources in Hokkaido Prefecture, Japan. J Infect Chemother 2008; 14:93-8. [PMID: 18622670 DOI: 10.1007/s10156-007-0583-y] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2007] [Accepted: 11/10/2007] [Indexed: 10/22/2022]
Abstract
Any increase in beta-lactam-resistant Haemophilus influenzae is a serious problem in respiratory and otolaryngology medicine. In this study, we examined the antibiotic susceptibility and genotype of 457 clinical Haemophilus influenzae strains isolated in Hokkaido Prefecture, Japan. Strains with beta-lactam-resistant mutations in gene encoding penicillin-binding protein 3 were more frequently found in lower respiratory tract specimens (sputa) than in upper respiratory tract specimens, such as rhinorrhea. The existence of the TEM-1 beta-lactamase gene occurred more frequently in adult patients than in pediatric patients. The results suggest that beta-lactam-resistant or nonsusceptible strains are more prevalent in adult patients with respiratory diseases. We observed only a very few strains which were nonsuscpetible to third-generation cephalosporins (CEPs) and carbapenems. However, 12%-13% of the strains were shown to be resistant to penicillins and second-generation CEPs, and approximately 4% of the strains were shown to be nonsusceptible to fourth-generation CEPs. In addition, we identified tetracycline-resistant (2.8%), chloramphenicol-resistant (0.6%), clarithromycin-resistant (2.6%), and fluoroquinolone-nonsusceptible (approximately 2%) H. influenzae strains.
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Affiliation(s)
- Yasuo Ohkoshi
- Department of Microbiology, Sapporo Medical University School of Medicine, Sapporo, 060-8556, Japan
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16
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Robertson GT, Doyle TB, Du Q, Duncan L, Mdluli KE, Lynch AS. A Novel indole compound that inhibits Pseudomonas aeruginosa growth by targeting MreB is a substrate for MexAB-OprM. J Bacteriol 2007; 189:6870-81. [PMID: 17644596 PMCID: PMC2045200 DOI: 10.1128/jb.00805-07] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Drug efflux systems contribute to the intrinsic resistance of Pseudomonas aeruginosa to many antibiotics and biocides and hamper research focused on the discovery and development of new antimicrobial agents targeted against this important opportunistic pathogen. Using a P. aeruginosa PAO1 derivative bearing deletions of opmH, encoding an outer membrane channel for efflux substrates, and four efflux pumps belonging to the resistance nodulation/cell division class including mexAB-oprM, we identified a small-molecule indole-class compound (CBR-4830) that is inhibitory to growth of this efflux-compromised strain. Genetic studies established MexAB-OprM as the principal pump for CBR-4830 and revealed MreB, a prokaryotic actin homolog, as the proximal cellular target of CBR-4830. Additional studies establish MreB as an essential protein in P. aeruginosa, and efflux-compromised strains treated with CBR-4830 transition to coccoid shape, consistent with MreB inhibition or depletion. Resistance genetics further suggest that CBR-4830 interacts with the putative ATP-binding pocket in MreB and demonstrate significant cross-resistance with A22, a structurally unrelated compound that has been shown to promote rapid dispersion of MreB filaments in vivo. Interestingly, however, ATP-dependent polymerization of purified recombinant P. aeruginosa MreB is blocked in vitro in a dose-dependent manner by CBR-4830 but not by A22. Neither compound exhibits significant inhibitory activity against mutant forms of MreB protein that bear mutations identified in CBR-4830-resistant strains. Finally, employing the strains and reagents prepared and characterized during the course of these studies, we have begun to investigate the ability of analogues of CBR-4830 to inhibit the growth of both efflux-proficient and efflux-compromised P. aeruginosa through specific inhibition of MreB function.
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Affiliation(s)
- Gregory T Robertson
- Cumbre Pharmaceuticals, Inc., 1502 Viceroy Drive, Dallas, TX 75235-2304, USA
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17
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Cerquetti M, Giufrè M, Cardines R, Mastrantonio P. First characterization of heterogeneous resistance to imipenem in invasive nontypeable Haemophilus influenzae isolates. Antimicrob Agents Chemother 2007; 51:3155-61. [PMID: 17620383 PMCID: PMC2043221 DOI: 10.1128/aac.00335-07] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
This study describes the first two reported invasive nontypeable Haemophilus influenzae (NTHI) isolates (strains 183 and 184) with heterogeneous resistance to imipenem. For both isolates, Etest showed imipenem MICs of > or =32 microg/ml. When the two strains were examined by the quantitative method of population analysis, both strain populations were heterogeneously resistant to imipenem and contained subpopulations growing in the presence of up to 32 microg of imipenem/ml at frequencies of 1.7 x 10(-5) and 1.5 x 10(-7), respectively. By pulsed-field gel electrophoresis analysis, the two isolates appeared to be genetically closely related. The sequencing of the ftsI gene encoding penicillin-binding protein 3 (PBP 3) and comparison with the sequence of the imipenem-susceptible H. influenzae strain Rd identified a pattern of six amino acid substitutions shared between strains 183 and 184; an additional change was unique to strain 183. No relationship between mutations in the dacB gene encoding PBP 4 and imipenem resistance was found. The replacement of the ftsI gene in the imipenem-susceptible strain Rd (for which the MIC of imipenem is 0.38 to 1 microg/ml) with ftsI from strain 183 resulted in a transformant for which the MIC of imipenem ranged from 4 to 8 microg/ml as determined by Etest. The Rd/183 transformant population showed heterogeneous resistance to imipenem; it contained subpopulations growing in the presence of up to 32 mug of imipenem/ml at a frequency of 3.3 x10(-8). The presence of additional resistance mechanisms, such as the overexpression of the AcrAB efflux pump, was investigated and does not seem to be involved. These data indicate that the heterogeneous imipenem resistance phenotype of our NTHI clone depends largely on the PBP 3 amino acid substitutions. We speculated that bacterial regulatory networks may play a role in the control of the heterogeneous expression of the resistance phenotype.
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Affiliation(s)
- Marina Cerquetti
- Department of Infectious, Parasitic and Immune-Mediated Diseases, Istituto Superiore di Sanità, Viale Regina Elena 299, 00161 Roma, Italy.
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18
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Dastidar V, Mao W, Lomovskaya O, Zgurskaya HI. Drug-induced conformational changes in multidrug efflux transporter AcrB from Haemophilus influenzae. J Bacteriol 2007; 189:5550-8. [PMID: 17526713 PMCID: PMC1951822 DOI: 10.1128/jb.00471-07] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
In gram-negative bacteria, transporters belonging to the resistance-nodulation-cell division (RND) superfamily of proteins are responsible for intrinsic multidrug resistance. Haemophilus influenzae, a gram-negative pathogen causing respiratory diseases in humans and animals, constitutively produces the multidrug efflux transporter AcrB (AcrB(HI)). Similar to other RND transporters AcrB(HI) associates with AcrA(HI), the periplasmic membrane fusion protein, and the outer membrane channel TolC(HI). Here, we report that AcrAB(HI) confers multidrug resistance when expressed in Escherichia coli and requires for its activity the E. coli TolC (TolC(EC)) protein. To investigate the intracellular dynamics of AcrAB(HI), single cysteine mutations were constructed in AcrB(HI) in positions previously identified as important for substrate recognition. The accessibility of these strategically positioned cysteines to the hydrophilic thiol-reactive fluorophore fluorescein-5-maleimide (FM) was studied in vivo in the presence of various substrates of AcrAB(HI) and in the presence or absence of AcrA(HI) and TolC(EC). We report that the reactivity of specific cysteines with FM is affected by the presence of some but not all substrates. Our results suggest that substrates induce conformational changes in AcrB(HI).
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Affiliation(s)
- Vishakha Dastidar
- Department of Chemistry and Biochemistry, 620 Parrington Oval, Norman, OK 73019, USA
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19
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Polleichtner G, Andersen C. The channel-tunnel HI1462 of Haemophilus influenzae reveals differences to Escherichia coli TolC. Microbiology (Reading) 2006; 152:1639-1647. [PMID: 16735727 DOI: 10.1099/mic.0.28805-0] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Efflux pumps play a major role in multidrug resistance of pathogenic bacteria. The TolC homologue HI1462 was identified as the single channel-tunnel in Haemophilus influenzae required to form a functional multidrug efflux pump. The outer-membrane protein was expressed in Escherichia coli, purified and reconstituted in black lipid membranes. It exhibited a comparatively small single-channel conductance of 43 pS in 1 M KCl and is the first known TolC homologue which is anion-selective. The HI1462 structure was modelled and an arginine residue lining the tunnel entrance was identified. The channel-tunnel of a mutant with the arginine substituted by an alanine residue was cation-selective and had a sevenfold higher single-channel conductance compared to wild-type. These results confirm that the arginine is responsible for anion selectivity and forms a salt bridge with a glutamate residue of the adjacent monomer, establishing a circular network, which keeps the tunnel entrance in a tightly closed conformation. In in vivo experiments, both the wild-type HI1462 and the mutant were able to substitute for E. coli TolC in the haemolysin secretion system, but not in the AcrAB/TolC multidrug efflux pump. The structure–function relationship of HI1462 is discussed in the context of the well-studied TolC channel-tunnel of E. coli.
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Affiliation(s)
- Georg Polleichtner
- Universität Würzburg, Lehrstuhl für Biotechnologie, Biozentrum der Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany
| | - Christian Andersen
- Universität Würzburg, Lehrstuhl für Biotechnologie, Biozentrum der Universität Würzburg, Am Hubland, D-97074 Würzburg, Germany
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21
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Bogdanovich T, Bozdogan B, Appelbaum PC. Effect of efflux on telithromycin and macrolide susceptibility in Haemophilus influenzae. Antimicrob Agents Chemother 2006; 50:893-8. [PMID: 16495248 PMCID: PMC1426444 DOI: 10.1128/aac.50.3.893-898.2006] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
This study investigated the presence of telithromycin and azithromycin efflux in 58 clinical strains of Haemophilus influenzae with various susceptibilities to macrolides, azalides, and ketolides. Efflux pumps were studied by measuring accumulation of radioactive [3H]telithromycin and [N-methyl-3H]azithromycin in the presence and absence of carbonyl m-chlorophenylhydrazone (CCCP), a protonophore. In 17 strains for which the telithromycin MICs were 0.06 to 0.5 microg/ml (azithromycin MICs, < or = 0.06 to 0.125 microg/ml; clarithromycin MICs, < or = 0.06 to 2 microg/ml), telithromycin and azithromycin accumulations were high without CCCP and not affected by its addition, which indicates absence of efflux. In 22 strains for which the telithromycin MICs were 0.25 to 4 microg/ml (azithromycin MICs, 0.25 to 1 microg/ml; clarithromycin MICs, 1 to 8 microg/ml), initially low levels of telithromycin accumulation became higher after addition of CCCP, indicating a functioning efflux pump. Nineteen strains for which the telithromycin MICs were > or = 2 microg/ml had efflux as well as various mutations in ribosomal proteins L4, L22, and/or 23S rRNA (domains II and V). Of these 19 strains, the telithromycin MICs (> or = 8 microg/ml) for 17 of them were significantly raised (azithromycin, MICs 4 to >32 microg/ml; clarithromycin MICs, 8 to >32 microg/ml). From these results we conclude that telithromycin efflux with or without additional ribosomal alterations is present in all H. influenzae strains, except for those for which the telithromycin MICs were very low.
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Affiliation(s)
- Tatiana Bogdanovich
- Department of Pathology, Hershey Medical Center, P.O. Box 850, Hershey, Pennsylvania 17033, USA
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22
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Song KH, Jung SJ, Seo YR, Kang SW, Han SS. Identification of up-regulated proteins in the hemolymph of immunized Bombyx mori larvae. COMPARATIVE BIOCHEMISTRY AND PHYSIOLOGY D-GENOMICS & PROTEOMICS 2006; 1:260-6. [PMID: 20483257 DOI: 10.1016/j.cbd.2006.01.001] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/04/2005] [Revised: 01/12/2006] [Accepted: 01/16/2006] [Indexed: 10/24/2022]
Abstract
Insects defend themselves against foreign invaders via both a cellular response and a humoral response. The objective of this study was to identify proteins which were differently regulated in the immunized Bombyx mori larvae. Heat-inactivated bacteria (Bacillus megaterium) were injected into B. mori larvae, 4 days after final ecdysis. After 6 h, we identified the immune proteins in the hemolymph which had been differentially regulated in the immune-challenged larvae, using two-dimensional polyacrylamide gel electrophoresis (2-D PAGE) and quadrupole time-of-flight (Q-TOF) tandem mass spectrometry (MS). After the bacterial injection, more than 30 spots determined to have been up-regulated, and 11 spots were down-regulated. The heat shock 70 kDa protein cognate was one of the up-regulated hemocytic proteins, and peptidoglycan recognition protein, antichymotrypsin precursor, and gloverin-like protein 1 approximately 4 were newly synthesized in the plasma. Antennal binding protein 7 was up-regulated in the plasma. Our results indicated that these immune response proteins were involved with the carrying out of innate immune responses.
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Affiliation(s)
- Kyung Han Song
- School of Life Science and Biotechnology, Korea University, Seoul 136-701, South Korea
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23
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Lynch AS. Efflux systems in bacterial pathogens: An opportunity for therapeutic intervention? An industry view. Biochem Pharmacol 2006; 71:949-56. [PMID: 16290174 DOI: 10.1016/j.bcp.2005.10.021] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/26/2005] [Revised: 10/05/2005] [Accepted: 10/11/2005] [Indexed: 11/19/2022]
Abstract
The efflux systems of bacteria protect cells from antibiotics and biocides by actively transporting compounds out of the cytoplasm and/or periplasm and thereby limit their steady-state accumulation at their site(s) of action. The impact of efflux systems on the efficacy of antibiotics used in human medicine and animal husbandry is becoming increasingly apparent from the characterization of drug-resistant strains with altered drug efflux properties. In most instances, efflux-mediated antibiotic resistance arises from mutational events that result in their elevated expression and, in the case of efflux pumps with broad substrate specificity, can confer multi-drug resistance (MDR) to structurally unrelated antibiotics. Knowledge of the role of efflux systems in conferring antibiotic resistance has now been successfully exploited in the pharmaceutical industry and contributed, in part, to the development of new members of the macrolide and tetracycline classes of antibiotics that circumvent the efflux-based resistance mechanisms that have limited the clinical utility of their progenitors. The therapeutic utility of compounds that inhibit bacterial drug efflux pumps and therein potentiate the activity of a co-administered antibiotic agent remains to be validated in the clinical setting, but the approach holds promise for the future in improving the efficacy and/or extending the clinical utility of existing antibiotics. This review discusses the potential of further exploiting the knowledge of efflux-mediated antibiotic resistance in bacteria toward the discovery and development of new chemotherapeutic agents.
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Affiliation(s)
- A Simon Lynch
- Cumbre Inc., 1502 Viceroy Drive, Dallas, TX 75235-2304, USA.
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Dean CR, Narayan S, Daigle DM, Dzink-Fox JL, Puyang X, Bracken KR, Dean KE, Weidmann B, Yuan Z, Jain R, Ryder NS. Role of the AcrAB-TolC efflux pump in determining susceptibility of Haemophilus influenzae to the novel peptide deformylase inhibitor LBM415. Antimicrob Agents Chemother 2005; 49:3129-35. [PMID: 16048914 PMCID: PMC1196275 DOI: 10.1128/aac.49.8.3129-3135.2005] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Haemophilus influenzae isolates vary widely in their susceptibilities to the peptide deformylase inhibitor LBM415 (MIC range, 0.06 to 32 microg/ml); however, on average, they are less susceptible than gram-positive organisms, such as Staphylococcus aureus and Streptococcus pneumoniae. Insertional inactivation of the H. influenzae acrB or tolC gene in strain NB65044 (Rd strain KW20) increased susceptibility to LBM415, confirming a role for the AcrAB-TolC pump in determining resistance. Consistent with this, sequencing of a PCR fragment generated with primers flanking the acrRA region from an LBM415-hypersusceptible H. influenzae clinical isolate revealed a genetic deletion of acrA. Inactivation of acrB or tolC in several clinical isolates with atypically reduced susceptibility to LBM415 (MIC of 16 microg/ml or greater) significantly increased susceptibility, confirming that the pump is also a determinant of decreased susceptibility in these clinical isolates. Examination of acrR, encoding the putative repressor of pump gene expression, from several of these strains revealed mutations introducing frameshifts, stop codons, and amino acid changes relative to the published sequence, suggesting that loss of pump repression leads to decreased susceptibility. Supporting this, NB65044 acrR mutants selected by exposure to LBM415 at 8 microg/ml had susceptibilities to LBM415 and other pump substrates comparable to the least sensitive clinical isolates and showed increased expression of pump genes.
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Affiliation(s)
- Charles R Dean
- Infectious Diseases, Novartis Institute for Biomedical Research, Inc., 100 Technology Square, Cambridge, MA 02139, USA.
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van Amsterdam K, Bart A, van der Ende A. A Helicobacter pylori TolC efflux pump confers resistance to metronidazole. Antimicrob Agents Chemother 2005; 49:1477-82. [PMID: 15793129 PMCID: PMC1068630 DOI: 10.1128/aac.49.4.1477-1482.2005] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
In Helicobacter pylori, the contribution of efflux proteins to antibiotic resistance is not well established. As translocases that act in parallel may have overlapping substrate specificities, the loss of function of one such translocase may be compensated for by that of another translocase with no effect on susceptibilities to antibiotics. The genome of H. pylori 26695 was assessed for the presence of putative translocases and outer membrane efflux or TolC-like proteins which could interact to form efflux systems involved in drug resistance. Twenty-seven translocases were identified, of which HP1184 was the sole representative of the multidrug and toxic compound extrusion family of translocases and which could thus have a unique substrate specificity. In addition, four TolC-like proteins (HP0605, HP0971, HP1327, and HP1489) were identified. Thus, it is feasible that inactivation of a TolC-like protein would affect the functions of multiple translocases. We aimed to determine whether efflux systems contribute to antimicrobial susceptibility by evaluation of the susceptibility profiles of an HP1184-knockout mutant, four mutants in which one of the four TolC homologs was inactivated, as well as a mutant in which both HP0605 and HP0971 were inactivated. The HP1184- and HP1489-knockout mutants both showed increased susceptibilities to ethidium bromide, while the HP0605-knockout mutant exhibited increased susceptibilities to novobiocin and sodium deoxycholate. The HP0605 and HP0971 double-knockout mutant was also more susceptible to metronidazole, in addition to being susceptible to novobiocin and sodium deoxycholate. Thus, active efflux is an eminent means of resistance to antimicrobials in H. pylori and resembles the situation in other bacteria.
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Affiliation(s)
- Karin van Amsterdam
- Department of Medical Microbiology, Academic Medical Center, P.O. Box 22660, 1100 DD Amsterdam, The Netherlands
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Trepod CM, Mott JE. Elucidation of essential and nonessential genes in the Haemophilus influenzae Rd cell wall biosynthetic pathway by targeted gene disruption. Antimicrob Agents Chemother 2005; 49:824-6. [PMID: 15673779 PMCID: PMC547210 DOI: 10.1128/aac.49.2.824-826.2005] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Targeted gene disruption by in vitro transposon mutagenesis has been used to identify the genes required for biosynthesis of the Haemophilus influenzae Rd cell wall under standard cultivation conditions. Of the 28 genes known to be associated with the cell wall biosynthetic pathway, 14 were determined to be essential.
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