201
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Abstract
Extreme antibiotic resistance in bacteria is associated with the expression of powerful inactivating enzymes and other functions encoded in accessory genomic elements. The contribution of core genome processes to high-level resistance in such bacteria has been unclear. In the work reported here, we evaluated the relative importance of core and accessory functions for high-level resistance to the aminoglycoside tobramycin in the nosocomial pathogen Acinetobacter baumannii. Three lines of evidence establish the primacy of core functions in this resistance. First, in a genome scale mutant analysis using transposon sequencing and validation with 594 individual mutants, nearly all mutations reducing tobramycin resistance inactivated core genes, some with stronger phenotypes than those caused by the elimination of aminoglycoside-inactivating enzymes. Second, the core functions mediating resistance were nearly identical in the wild type and a deletion mutant lacking a genome resistance island that encodes the inactivating enzymes. Thus, most or all of the core resistance determinants important in the absence of the enzymes are also important in their presence. Third, reductions in tobramycin resistance caused by different core mutations were additive, and highly sensitive double and triple mutants (with 250-fold reductions in the MIC) that retained accessory resistance genes could be constructed. Core processes that contribute most strongly to intrinsic tobramycin resistance include phospholipid biosynthesis, phosphate regulation, and envelope homeostasis. The inexorable increase in bacterial antibiotic resistance threatens to undermine many of the procedures that transformed medicine in the last century. One strategy to meet the challenge antibiotic resistance poses is the development of drugs that undermine resistance. To identify potential targets for such adjuvants, we identified the functions underlying resistance to an important class of antibiotics for one of the most highly resistant pathogens known.
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202
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Wang Y, Mowla R, Ji S, Guo L, De Barros Lopes MA, Jin C, Song D, Ma S, Venter H. Design, synthesis and biological activity evaluation of novel 4-subtituted 2-naphthamide derivatives as AcrB inhibitors. Eur J Med Chem 2017; 143:699-709. [PMID: 29220791 DOI: 10.1016/j.ejmech.2017.11.102] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2017] [Revised: 11/14/2017] [Accepted: 11/29/2017] [Indexed: 10/18/2022]
Abstract
A novel series of 4-substituted 2-naphthamide derivatives were designed, synthesized and evaluated for their biological activity. In particular, the ability of the compounds to potentiate the action of antibiotics, to inhibit Nile Red efflux and to target AcrB specifically was investigated. The results indicated that most of the 4-substituted 2-naphthamide derivatives were able to synergize with the antibiotics tested, and inhibit Nile Red efflux by AcrB in the resistant phenotype. Subsequent exclusion of compounds with off target effects such as outer- or inner membrane permeabilization identified compounds 7c, 7g, 12c, 12i and 13g as efflux pump inhibitors (EPIs). Particularly, compounds 7c, 7g and 12i were found to be the most potent EPIs, which synergized with the two substrates tested at lower concentrations than that of parent A3, demonstrating an improvement in potency as compared to A3. Additionally, when the outer membrane of E. coli was permeabilized, compound 12c displayed a huge increase in efficacy and was able to synergize with erythromycin at a concentration that was 16 times lower than that of the parent A3. Hence we were able to design and synthesize compounds that displayed significant increase in efficacy as EPIs against AcrB.
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Affiliation(s)
- Yinhu Wang
- Department of Medicinal Chemistry, Key Laboratory of Chemical Biology (Ministry of Education), School of Pharmaceutical Sciences, Shandong University, 44 West Culture Road, Jinan 250012, China
| | - Rumana Mowla
- School of Pharmacy and Medical Sciences, Sansom Institute for Health Research, University of South Australia, Adelaide, SA 5000, Australia
| | - Shengli Ji
- ReaLi Tide Biological Technology (Weihai) Co. Ltd, Weihai 264207, China
| | - Liwei Guo
- Department of Medicinal Chemistry, Key Laboratory of Chemical Biology (Ministry of Education), School of Pharmaceutical Sciences, Shandong University, 44 West Culture Road, Jinan 250012, China
| | - Miguel A De Barros Lopes
- School of Pharmacy and Medical Sciences, Sansom Institute for Health Research, University of South Australia, Adelaide, SA 5000, Australia
| | - Chaobin Jin
- Department of Medicinal Chemistry, Key Laboratory of Chemical Biology (Ministry of Education), School of Pharmaceutical Sciences, Shandong University, 44 West Culture Road, Jinan 250012, China
| | - Di Song
- Department of Medicinal Chemistry, Key Laboratory of Chemical Biology (Ministry of Education), School of Pharmaceutical Sciences, Shandong University, 44 West Culture Road, Jinan 250012, China
| | - Shutao Ma
- Department of Medicinal Chemistry, Key Laboratory of Chemical Biology (Ministry of Education), School of Pharmaceutical Sciences, Shandong University, 44 West Culture Road, Jinan 250012, China.
| | - Henrietta Venter
- School of Pharmacy and Medical Sciences, Sansom Institute for Health Research, University of South Australia, Adelaide, SA 5000, Australia.
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203
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Briffotaux J, Huang W, Wang X, Gicquel B. MmpS5/MmpL5 as an efflux pump in Mycobacterium species. Tuberculosis (Edinb) 2017; 107:13-19. [DOI: 10.1016/j.tube.2017.08.001] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2017] [Revised: 07/31/2017] [Accepted: 08/03/2017] [Indexed: 10/19/2022]
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204
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López CA, Travers T, Pos KM, Zgurskaya HI, Gnanakaran S. Dynamics of Intact MexAB-OprM Efflux Pump: Focusing on the MexA-OprM Interface. Sci Rep 2017; 7:16521. [PMID: 29184094 PMCID: PMC5705723 DOI: 10.1038/s41598-017-16497-w] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2017] [Accepted: 10/30/2017] [Indexed: 11/30/2022] Open
Abstract
Antibiotic efflux is one of the most critical mechanisms leading to bacterial multidrug resistance. Antibiotics are effluxed out of the bacterial cell by a tripartite efflux pump, a complex machinery comprised of outer membrane, periplasmic adaptor, and inner membrane protein components. Understanding the mechanism of efflux pump assembly and its dynamics could facilitate discovery of novel approaches to counteract antibiotic resistance in bacteria. We built here an intact atomistic model of the Pseudomonas aeruginosa MexAB-OprM pump in a Gram-negative membrane model that contained both inner and outer membranes separated by a periplasmic space. All-atom molecular dynamics (MD) simulations confirm that the fully assembled pump is stable in the microsecond timescale. Using a combination of all-atom and coarse-grained MD simulations and sequence covariation analysis, we characterized the interface between MexA and OprM in the context of the entire efflux pump. These analyses suggest a plausible mechanism by which OprM is activated via opening of its periplasmic aperture through a concerted interaction with MexA.
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Affiliation(s)
- Cesar A López
- Theoretical Biology and Biophysics Group, Los Alamos National Laboratory, Los Alamos, New Mexico, 87545, United States
| | - Timothy Travers
- Theoretical Biology and Biophysics Group, Los Alamos National Laboratory, Los Alamos, New Mexico, 87545, United States.,Center for Nonlinear Sciences, Los Alamos National Laboratory, Los Alamos, New Mexico, 87545, United States
| | - Klaas M Pos
- Institute of Biochemistry, Goethe University, Frankfurt am Main, Germany.,Cluster of Excellence Frankfurt, Goethe University, Frankfurt am Main, Germany
| | - Helen I Zgurskaya
- Department of Chemistry and Biochemistry, University of Oklahoma, 101 Stephenson Parkway, Norman, Oklahoma, 73019, United States
| | - S Gnanakaran
- Theoretical Biology and Biophysics Group, Los Alamos National Laboratory, Los Alamos, New Mexico, 87545, United States.
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205
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Weston N, Sharma P, Ricci V, Piddock LJV. Regulation of the AcrAB-TolC efflux pump in Enterobacteriaceae. Res Microbiol 2017; 169:425-431. [PMID: 29128373 DOI: 10.1016/j.resmic.2017.10.005] [Citation(s) in RCA: 82] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2017] [Revised: 10/16/2017] [Accepted: 10/31/2017] [Indexed: 11/18/2022]
Abstract
Bacterial multidrug efflux systems are a major mechanism of antimicrobial resistance and are fundamental to the physiology of Gram-negative bacteria. The resistance-nodulation-division (RND) family of efflux pumps is the most clinically significant, as it is associated with multidrug resistance. Expression of efflux systems is subject to multiple levels of regulation, involving local and global transcriptional regulation as well as post-transcriptional and post-translational regulation. The best-characterised RND system is AcrAB-TolC, which is present in Enterobacteriaceae. This review describes the current knowledge and new data about the regulation of the acrAB and tolC genes in Escherichia coli and Salmonella enterica.
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Affiliation(s)
- Natasha Weston
- Institute of Microbiology and Infection, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - Prateek Sharma
- Institute of Microbiology and Infection, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - Vito Ricci
- Institute of Microbiology and Infection, University of Birmingham, Birmingham B15 2TT, United Kingdom
| | - Laura J V Piddock
- Institute of Microbiology and Infection, University of Birmingham, Birmingham B15 2TT, United Kingdom.
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206
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Praski Alzrigat L, Huseby DL, Brandis G, Hughes D. Fitness cost constrains the spectrum of marR mutations in ciprofloxacin-resistant Escherichia coli. J Antimicrob Chemother 2017; 72:3016-3024. [PMID: 28962020 PMCID: PMC5890708 DOI: 10.1093/jac/dkx270] [Citation(s) in RCA: 30] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2017] [Revised: 06/12/2017] [Accepted: 07/07/2017] [Indexed: 12/26/2022] Open
Abstract
OBJECTIVES To determine whether the spectrum of mutations in marR in ciprofloxacin-resistant clinical isolates of Escherichia coli shows evidence of selection bias, either to reduce fitness costs, or to increase drug resistance. MarR is a repressor protein that regulates, via MarA, expression of the Mar regulon, including the multidrug efflux pump AcrAB-TolC. METHODS Isogenic strains carrying 36 different marR alleles identified in resistant clinical isolates, or selected for resistance in vitro, were constructed. Drug susceptibility and relative fitness in growth competition assays were measured for all strains. The expression level of marA, and of various efflux pump components, as a function of specific mutations in marR, was measured by qPCR. RESULTS The spectrum of genetic alterations in marR in clinical isolates is strongly biased against inactivating mutations. In general, the alleles found in clinical isolates conferred a lower level of resistance and imposed a lower growth fitness cost than mutations selected in vitro. The level of expression of MarA correlated well with the MIC of ciprofloxacin. This supports the functional connection between mutations in marR and reduced susceptibility to ciprofloxacin. CONCLUSIONS Mutations in marR selected in ciprofloxacin-resistant clinical isolates are strongly biased against inactivating mutations. Selection favours mutant alleles that have the lowest fitness costs, even though these cause only modest reductions in drug susceptibility. This suggests that selection for high relative fitness is more important than selection for increased resistance in determining which alleles of marR will be selected in resistant clinical isolates.
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Affiliation(s)
- Lisa Praski Alzrigat
- Department of Medical Biochemistry and Microbiology, Uppsala University, Biomedical Center Box 582, Husargatan 3, S-75123 Uppsala, Sweden
| | - Douglas L Huseby
- Department of Medical Biochemistry and Microbiology, Uppsala University, Biomedical Center Box 582, Husargatan 3, S-75123 Uppsala, Sweden
| | - Gerrit Brandis
- Department of Medical Biochemistry and Microbiology, Uppsala University, Biomedical Center Box 582, Husargatan 3, S-75123 Uppsala, Sweden
| | - Diarmaid Hughes
- Department of Medical Biochemistry and Microbiology, Uppsala University, Biomedical Center Box 582, Husargatan 3, S-75123 Uppsala, Sweden
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207
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Zwama M, Hayashi K, Sakurai K, Nakashima R, Kitagawa K, Nishino K, Yamaguchi A. Hoisting-Loop in Bacterial Multidrug Exporter AcrB Is a Highly Flexible Hinge That Enables the Large Motion of the Subdomains. Front Microbiol 2017; 8:2095. [PMID: 29118749 PMCID: PMC5661021 DOI: 10.3389/fmicb.2017.02095] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2017] [Accepted: 10/12/2017] [Indexed: 01/21/2023] Open
Abstract
The overexpression of RND-type exporters is one of the main causes of multidrug resistance (MDR) in Gram-negative pathogens. In RND transporters, such as Escherichia coli's main efflux pump AcrB, drug efflux occurs in the porter domain, while protons flow through the transmembrane domain: remote conformational coupling. At the border of a transmembrane helix (TM8) and subdomain PC2, there is a loop which makes a hoisting movement by a random-coil-to-α-helix change, and opens and closes a drug channel entrance. This loop is supposed to play a key role in the allosteric conformational coupling between the transmembrane and porter domain. Here we show the results of a series of flexibility loop-mutants of AcrB. We determined the crystal structure of a three amino acid truncated loop mutant, which is still a functional transporter, and show that the short α-helix between Cβ15 and the loop unwinds to a random coil in the access and binding monomers and in the extrusion monomer it makes a partially stretched coil-to-helix change. The loop has undergone compensatory conformational changes and still facilitates the opening and closing of the channel. In addition, more flexible mutated loops (proline mutated and significantly elongated) can still function during export. The flexibility in this region is however limited, as an even more truncated mutant (six amino acid deletion) becomes mostly inactive. We found that the hoisting-loop is a highly flexible hinge that enables the conformational energy transmission passively.
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Affiliation(s)
- Martijn Zwama
- Department of Cell Membrane Structural Biology, Institute of Scientific and Industrial Research, Osaka University, Osaka, Japan.,Department of Biomolecular Science and Regulation, Institute of Scientific and Industrial Research, Osaka University, Osaka, Japan.,Graduate School of Pharmaceutical Sciences, Osaka University, Osaka, Japan
| | - Katsuhiko Hayashi
- Department of Cell Membrane Structural Biology, Institute of Scientific and Industrial Research, Osaka University, Osaka, Japan.,Department of Biomolecular Science and Regulation, Institute of Scientific and Industrial Research, Osaka University, Osaka, Japan
| | - Keisuke Sakurai
- Department of Cell Membrane Structural Biology, Institute of Scientific and Industrial Research, Osaka University, Osaka, Japan
| | - Ryosuke Nakashima
- Department of Cell Membrane Structural Biology, Institute of Scientific and Industrial Research, Osaka University, Osaka, Japan
| | - Kimie Kitagawa
- Department of Cell Membrane Structural Biology, Institute of Scientific and Industrial Research, Osaka University, Osaka, Japan
| | - Kunihiko Nishino
- Department of Biomolecular Science and Regulation, Institute of Scientific and Industrial Research, Osaka University, Osaka, Japan
| | - Akihito Yamaguchi
- Department of Cell Membrane Structural Biology, Institute of Scientific and Industrial Research, Osaka University, Osaka, Japan
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208
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Mowla R, Wang Y, Ma S, Venter H. Kinetic analysis of the inhibition of the drug efflux protein AcrB using surface plasmon resonance. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2017; 1860:878-886. [PMID: 28890187 DOI: 10.1016/j.bbamem.2017.08.024] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2017] [Revised: 08/19/2017] [Accepted: 08/31/2017] [Indexed: 11/24/2022]
Abstract
Multidrug efflux protein complexes such as AcrAB-TolC from Escherichia coli are paramount in multidrug resistance in Gram-negative bacteria and are also implicated in other processes such as virulence and biofilm formation. Hence efflux pump inhibition, as a means to reverse antimicrobial resistance in clinically relevant pathogens, has gained increased momentum over the past two decades. Significant advances in the structural and functional analysis of AcrB have informed the selection of efflux pump inhibitors (EPIs). However, an accurate method to determine the kinetics of efflux pump inhibition was lacking. In this study we standardised and optimised surface plasmon resonance (SPR) to probe the binding kinetics of substrates and inhibitors to AcrB. The SPR method was also combined with a fluorescence drug binding method by which affinity of two fluorescent AcrB substrates were determined using the same conditions and controls as for SPR. Comparison of the results from the fluorescent assay to those of the SPR assay showed excellent correlation and provided validation for the methods and conditions used for SPR. The kinetic parameters of substrate (doxorubicin, novobiocin and minocycline) binding to AcrB were subsequently determined. Lastly, the kinetics of inhibition of AcrB were probed for two established inhibitors (phenylalanine arginyl β-naphthylamide and 1-1-naphthylmethyl-piperazine) and three novel EPIs: 4-isobutoxy-2-naphthamide (A2), 4-isopentyloxy-2-naphthamide (A3) and 4-benzyloxy-2-naphthamide (A9) have also been probed. The kinetic data obtained could be correlated with inhibitor efficacy and mechanism of action. This study is the first step in the quantitative analysis of the kinetics of inhibition of the clinically important RND-class of multidrug efflux pumps and will allow the design of improved and more potent inhibitors of drug efflux pumps. This article is part of a Special Issue entitled: Beyond the Structure-Function Horizon of Membrane Proteins edited by Ute Hellmich, Rupak Doshi and Benjamin McIlwain.
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Affiliation(s)
- Rumana Mowla
- School of Pharmacy and Medical Sciences, Sansom Institute for Health Research, University of South Australia, SA 5000, Australia
| | - Yinhu Wang
- Department of Medicinal Chemistry, Key Laboratory of Chemical Biology, School of Pharmaceutical Sciences, Shandong University, Jinan 250012, China
| | - Shutao Ma
- Department of Medicinal Chemistry, Key Laboratory of Chemical Biology, School of Pharmaceutical Sciences, Shandong University, Jinan 250012, China
| | - Henrietta Venter
- School of Pharmacy and Medical Sciences, Sansom Institute for Health Research, University of South Australia, SA 5000, Australia.
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209
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Fluoroquinolone structure and translocation flux across bacterial membrane. Sci Rep 2017; 7:9821. [PMID: 28851902 PMCID: PMC5575017 DOI: 10.1038/s41598-017-08775-4] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2017] [Accepted: 07/18/2017] [Indexed: 12/19/2022] Open
Abstract
Bacterial multidrug resistance is a worrying health issue. In Gram-negative antibacterial research, the challenge is to define the antibiotic permeation across the membranes. Passing through the membrane barrier to reach the inhibitory concentration inside the bacterium is a pivotal step for antibacterial molecules. A spectrofluorimetric methodology has been developed to detect fluoroquinolones in bacterial population and inside individual Gram-negative bacterial cells. In this work, we studied the antibiotic accumulation in cells expressing various levels of efflux pumps. The assays allow us to determine the intracellular concentration of the fluoroquinolones to study the relationships between the level of efflux activity and the antibiotic accumulation, and finally to evaluate the impact of fluoroquinolone structures in this process. This represents the first protocol to identify some structural parameters involved in antibiotic translocation and accumulation, and to illustrate the recently proposed “Structure Intracellular Concentration Activity Relationship” (SICAR) concept.
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210
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Cerminati S, Giri GF, Mendoza JI, Soncini FC, Checa SK. The CpxR/CpxA system contributes to Salmonella gold-resistance by controlling the GolS-dependent gesABC transcription. Environ Microbiol 2017. [PMID: 28631419 DOI: 10.1111/1462-2920.13837] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Several regulatory systems contribute to bacterial resistance to heavy metals controlling the expression of factors required to eliminate the intoxicant and/or to repair the damage caused by it. In Salmonella, the response to Au ions is mediated by the specific metalloregulator GolS that, among other genes, controls the expression of the RND-efflux pump GesABC. In this work, we demonstrate that CpxR/CpxA, a main cell-envelope stress-responding system, promotes gesABC transcription in the presence of Au ions at neutral pH. Deletion of either cpxA or cpxR, or mutation of the CpxR-binding site identified upstream of the GolS-operator in the gesABC promoter region reduces but does not abrogate the GolS- and Au-dependent activation of gesABC. Au also triggers the activation of the CpxR/CpxA system and deletion of the cpxRA operon severely reduces survival in the presence of the toxic metal. Our results indicate that the coordinated action of GolS and CpxR/CpxA contribute to protecting the cell from severe Au damage.
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Affiliation(s)
- Sebastián Cerminati
- Instituto de Biología Molecular y Celular de Rosario (IBR), Universidad Nacional de Rosario (UNR), CONICET y Departamento de Microbiología, Facultad de Ciencias Bioquímicas y Farmacéuticas, UNR, Ocampo y Esmeralda, Rosario, Argentina
| | - Germán F Giri
- Instituto de Biología Molecular y Celular de Rosario (IBR), Universidad Nacional de Rosario (UNR), CONICET y Departamento de Microbiología, Facultad de Ciencias Bioquímicas y Farmacéuticas, UNR, Ocampo y Esmeralda, Rosario, Argentina
| | - Julián I Mendoza
- Instituto de Biología Molecular y Celular de Rosario (IBR), Universidad Nacional de Rosario (UNR), CONICET y Departamento de Microbiología, Facultad de Ciencias Bioquímicas y Farmacéuticas, UNR, Ocampo y Esmeralda, Rosario, Argentina
| | - Fernando C Soncini
- Instituto de Biología Molecular y Celular de Rosario (IBR), Universidad Nacional de Rosario (UNR), CONICET y Departamento de Microbiología, Facultad de Ciencias Bioquímicas y Farmacéuticas, UNR, Ocampo y Esmeralda, Rosario, Argentina
| | - Susana K Checa
- Instituto de Biología Molecular y Celular de Rosario (IBR), Universidad Nacional de Rosario (UNR), CONICET y Departamento de Microbiología, Facultad de Ciencias Bioquímicas y Farmacéuticas, UNR, Ocampo y Esmeralda, Rosario, Argentina
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211
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Analysis of Shigella flexneri Resistance, Biofilm Formation, and Transcriptional Profile in Response to Bile Salts. Infect Immun 2017; 85:IAI.01067-16. [PMID: 28348056 DOI: 10.1128/iai.01067-16] [Citation(s) in RCA: 60] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2016] [Accepted: 03/23/2017] [Indexed: 01/07/2023] Open
Abstract
The Shigella species cause millions of cases of watery or bloody diarrhea each year, mostly in children in developing countries. While many aspects of Shigella colonic cell invasion are known, crucial gaps in knowledge regarding how the bacteria survive, transit, and regulate gene expression prior to infection remain. In this study, we define mechanisms of resistance to bile salts and build on previous research highlighting induced virulence in Shigella flexneri strain 2457T following exposure to bile salts. Typical growth patterns were observed within the physiological range of bile salts; however, growth was inhibited at higher concentrations. Interestingly, extended periods of exposure to bile salts led to biofilm formation, a conserved phenotype that we observed among members of the Enterobacteriaceae Characterization of S. flexneri 2457T biofilms determined that both bile salts and glucose were required for formation, dispersion was dependent upon bile salts depletion, and recovered bacteria displayed induced adherence to HT-29 cells. RNA-sequencing analysis verified an important bile salt transcriptional profile in S. flexneri 2457T, including induced drug resistance and virulence gene expression. Finally, functional mutagenesis identified the importance of the AcrAB efflux pump and lipopolysaccharide O-antigen synthesis for bile salt resistance. Our data demonstrate that S. flexneri 2457T employs multiple mechanisms to survive exposure to bile salts, which may have important implications for multidrug resistance. Furthermore, our work confirms that bile salts are important physiological signals to activate S. flexneri 2457T virulence. This work provides insights into how exposure to bile likely regulates Shigella survival and virulence during host transit and subsequent colonic infection.
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212
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Klahn P, Brönstrup M. Bifunctional antimicrobial conjugates and hybrid antimicrobials. Nat Prod Rep 2017; 34:832-885. [PMID: 28530279 DOI: 10.1039/c7np00006e] [Citation(s) in RCA: 119] [Impact Index Per Article: 17.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Covering: up to the end of 2016Novel antimicrobial drugs are continuously needed to counteract bacterial resistance development. An innovative molecular design strategy for novel antibiotic drugs is based on the hybridization of an antibiotic with a second functional entity. Such conjugates can be grouped into two major categories. In the first category (antimicrobial hybrids), both functional elements of the hybrid exert antimicrobial activity. Due to the dual targeting, resistance development can be significantly impaired, the pharmacokinetic properties can be superior compared to combination therapies with the single antibiotics, and the antibacterial potency is often enhanced in a synergistic manner. In the second category (antimicrobial conjugates), one functional moiety controls the accumulation of the other part of the conjugate, e.g. by mediating an active transport into the bacterial cell or blocking the efflux. This approach is mostly applied to translocate compounds across the cell envelope of Gram-negative bacteria through membrane-embedded transporters (e.g. siderophore transporters) that provide nutrition and signalling compounds to the cell. Such 'Trojan Horse' approaches can expand the antibacterial activity of compounds against Gram-negative pathogens, or offer new options for natural products that could not be developed as standalone antibiotics, e.g. due to their toxicity.
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Affiliation(s)
- P Klahn
- Department for Chemical Biology, Helmholtz Centre for Infection Research, Inhoffenstraße 7, 38124 Braunschweig, Germany. and Institute for Organic Chemistry, Technische Universität Braunschweig, Hagenring 30, 38106 Braunschweig, Germany.
| | - M Brönstrup
- Department for Chemical Biology, Helmholtz Centre for Infection Research, Inhoffenstraße 7, 38124 Braunschweig, Germany.
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213
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Cansizoglu MF, Toprak E. Fighting against evolution of antibiotic resistance by utilizing evolvable antimicrobial drugs. Curr Genet 2017; 63:973-976. [PMID: 28497241 DOI: 10.1007/s00294-017-0703-x] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/24/2017] [Revised: 05/03/2017] [Accepted: 05/05/2017] [Indexed: 12/24/2022]
Abstract
Antibiotic resistance is a worldwide public health problem (Bush et al. in Nat Rev Microbiol 9:894-896, 2011). The lack of effective therapies against resistant bacteria globally leads to prolonged treatments, increased mortality, and inflating health care costs (Oz et al. in Mol Biol Evol 31:2387-2401, 2014; Martinez in Science 321:365-367, 2008; Lipsitch et al. in Proc Natl Acad Sci USA 97:1938-1943, 2000; Taubes in Science 321:356-361, 2008; Laxminarayan et al. in Lancet, 2016; Laxminarayan et al. in Lancet Infect Dis 13:1057-1098, 2013). Current efforts towards a solution of this problem can be boiled down to two main strategies: (1) developing of new antimicrobial agents and (2) searching for smart strategies that can restore or preserve the efficacy of existing antimicrobial agents. In this short review article, we discuss the need for evolvable antimicrobial agents, focusing on a new antimicrobial technology that utilizes peptide-conjugated phosphorodiamidate morpholino oligomers to inhibit the growth of pathogenic bacteria by targeting bacterial genes.
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Affiliation(s)
- Mehmet Fatih Cansizoglu
- Green Center for Systems Biology, University of Texas Southwestern Medical Center, Dallas, TX, USA
| | - Erdal Toprak
- Green Center for Systems Biology, University of Texas Southwestern Medical Center, Dallas, TX, USA. .,Department of Pharmacology, University of Texas Southwestern Medical Center, Dallas, TX, USA.
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214
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Bruns MM, Kakarla P, Floyd JT, Mukherjee MM, Ponce RC, Garcia JA, Ranaweera I, Sanford LM, Hernandez AJ, Willmon TM, Tolson GL, Varela MF. Modulation of the multidrug efflux pump EmrD-3 from Vibrio cholerae by Allium sativum extract and the bioactive agent allyl sulfide plus synergistic enhancement of antimicrobial susceptibility by A. sativum extract. Arch Microbiol 2017; 199:1103-1112. [PMID: 28432381 DOI: 10.1007/s00203-017-1378-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2016] [Revised: 03/25/2017] [Accepted: 04/03/2017] [Indexed: 10/19/2022]
Abstract
The causative agent of cholera, Vibrio cholerae, is a public health concern. Multidrug-resistant V. cholerae variants may reduce chemotherapeutic efficacies of severe cholera. We previously reported that the multidrug efflux pump EmrD-3 from V. cholerae confers resistance to multiple structurally distinct antimicrobials. Medicinal plant compounds are potential candidates for EmrD-3 efflux pump modulation. The antibacterial activities of garlic Allium sativum, although poorly understood, predicts that a main bioactive component, allyl sulfide, modulates EmrD-3 efflux. Thus, we tested whether A. sativum extract acts in synergy with antimicrobials and that a main bioactive component allyl sulfide inhibits EmrD-3 efflux. We found that A. sativum extract and allyl sulfide inhibited ethidium bromide efflux in cells harboring EmrD-3 and that A. sativum lowered the MICs of multiple antibacterials. We conclude that A. sativum and allyl sulfide inhibit EmrD-3 and that A. sativum extract synergistically enhances antibacterial agents.
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Affiliation(s)
- Merissa M Bruns
- Department of Biology, Eastern New Mexico University, Portales, NM, 88130, USA
| | - Prathusha Kakarla
- Department of Biology, Eastern New Mexico University, Portales, NM, 88130, USA
| | - Jared T Floyd
- Department of Biology, Eastern New Mexico University, Portales, NM, 88130, USA
| | - Mun Mun Mukherjee
- Department of Biology, Eastern New Mexico University, Portales, NM, 88130, USA
| | - Robert C Ponce
- Department of Biology, Eastern New Mexico University, Portales, NM, 88130, USA
| | - John A Garcia
- Department of Biology, Eastern New Mexico University, Portales, NM, 88130, USA
| | - Indrika Ranaweera
- Department of Biology, Eastern New Mexico University, Portales, NM, 88130, USA
| | - Leslie M Sanford
- Department of Biology, Eastern New Mexico University, Portales, NM, 88130, USA
| | - Alberto J Hernandez
- Department of Biology, Eastern New Mexico University, Portales, NM, 88130, USA
| | - T Mark Willmon
- Department of Biology, Eastern New Mexico University, Portales, NM, 88130, USA
| | - Grace L Tolson
- Department of Biology, Eastern New Mexico University, Portales, NM, 88130, USA
| | - Manuel F Varela
- Department of Biology, Eastern New Mexico University, Portales, NM, 88130, USA.
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215
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Computational modelling of efflux pumps and their inhibitors. Essays Biochem 2017; 61:141-156. [PMID: 28258237 DOI: 10.1042/ebc20160065] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2016] [Revised: 12/13/2016] [Accepted: 12/19/2016] [Indexed: 11/17/2022]
Abstract
Antimicrobial resistance is based on the multifarious strategies that bacteria adopt to face antibiotic therapies, making it a key public health concern of our era. Among these strategies, efflux pumps (EPs) contribute significantly to increase the levels and profiles of resistance by expelling a broad range of unrelated compounds - buying time for the organisms to develop specific resistance. In Gram-negative bacteria, many of these chromosomally encoded transporters form multicomponent 'pumps' that span both inner and outer membranes and are driven energetically by a primary or secondary transporter component.One of the strategies to reinvigorate the efficacy of antimicrobials is by joint administration with EP inhibitors (EPI), which either block the substrate binding and/or hinder any of the transport-dependent steps of the pump. In this review, we provide an overview of multidrug-resistance EPs, their inhibition strategies and the relevant findings from the various computational simulation studies reported to date with respect to deciphering the mechanism of action of inhibitors with the purpose of improving their rational design.
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216
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Intrinsic, adaptive and acquired antimicrobial resistance in Gram-negative bacteria. Essays Biochem 2017; 61:49-59. [DOI: 10.1042/ebc20160063] [Citation(s) in RCA: 96] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2016] [Revised: 01/18/2017] [Accepted: 01/23/2017] [Indexed: 12/31/2022]
Abstract
Gram-negative bacteria are responsible for a large proportion of antimicrobial-resistant infections in humans and animals. Among this class of bacteria are also some of the most successful environmental organisms. Part of this success is their adaptability to a variety of different niches, their intrinsic resistance to antimicrobial drugs and their ability to rapidly acquire resistance mechanisms. These mechanisms of resistance are not exclusive and the interplay of several mechanisms causes high levels of resistance. In this review, we explore the molecular mechanisms underlying resistance in Gram-negative organisms and how these different mechanisms enable them to survive many different stress conditions.
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217
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Tan Z, Black W, Yoon JM, Shanks JV, Jarboe LR. Improving Escherichia coli membrane integrity and fatty acid production by expression tuning of FadL and OmpF. Microb Cell Fact 2017; 16:38. [PMID: 28245829 PMCID: PMC5331629 DOI: 10.1186/s12934-017-0650-8] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2016] [Accepted: 02/22/2017] [Indexed: 11/26/2022] Open
Abstract
Background Construction of microbial biocatalysts for the production of biorenewables at economically viable yields and titers is frequently hampered by product toxicity. Membrane damage is often deemed as the principal mechanism of this toxicity, particularly in regards to decreased membrane integrity. Previous studies have attempted to engineer the membrane with the goal of increasing membrane integrity. However, most of these works focused on engineering of phospholipids and efforts to identify membrane proteins that can be targeted to improve fatty acid production have been unsuccessful. Results Here we show that deletion of outer membrane protein ompF significantly increased membrane integrity, fatty acid tolerance and fatty acid production, possibly due to prevention of re-entry of short chain fatty acids. In contrast, deletion of fadL resulted in significantly decreased membrane integrity and fatty acid production. Consistently, increased expression of fadL remarkably increased membrane integrity and fatty acid tolerance while also increasing the final fatty acid titer. This 34% increase in the final fatty acid titer was possibly due to increased membrane lipid biosynthesis. Tuning of fadL expression showed that there is a positive relationship between fadL abundance and fatty acid production. Combinatorial deletion of ompF and increased expression of fadL were found to have an additive role in increasing membrane integrity, and was associated with a 53% increase the fatty acid titer, to 2.3 g/L. Conclusions These results emphasize the importance of membrane proteins for maintaining membrane integrity and production of biorenewables, such as fatty acids, which expands the targets for membrane engineering. Electronic supplementary material The online version of this article (doi:10.1186/s12934-017-0650-8) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Zaigao Tan
- 4134 Biorenewables Research Laboratory, Department of Chemical and Biological Engineering, Iowa State University, Ames, IA, 50011, USA
| | - William Black
- 4134 Biorenewables Research Laboratory, Department of Chemical and Biological Engineering, Iowa State University, Ames, IA, 50011, USA.,Department of Chemical Engineering and Materials Sciences, University of California, 916 Engineering Tower Irvine, Irvine, CA, 92697-2575, USA
| | - Jong Moon Yoon
- 4134 Biorenewables Research Laboratory, Department of Chemical and Biological Engineering, Iowa State University, Ames, IA, 50011, USA
| | - Jacqueline V Shanks
- 4134 Biorenewables Research Laboratory, Department of Chemical and Biological Engineering, Iowa State University, Ames, IA, 50011, USA
| | - Laura R Jarboe
- 4134 Biorenewables Research Laboratory, Department of Chemical and Biological Engineering, Iowa State University, Ames, IA, 50011, USA.
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218
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The Impact of Efflux Pump Inhibitors on the Activity of Selected Non-Antibiotic Medicinal Products against Gram-Negative Bacteria. Molecules 2017; 22:molecules22010114. [PMID: 28085074 PMCID: PMC6155833 DOI: 10.3390/molecules22010114] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2016] [Revised: 12/12/2016] [Accepted: 01/04/2017] [Indexed: 11/22/2022] Open
Abstract
The potential role of non-antibiotic medicinal products in the treatment of multidrug-resistant Gram-negative bacteria has recently been investigated. It is highly likely that the presence of efflux pumps may be one of the reasons for the weak activity of non-antibiotics, as in the case of some non-steroidal anti-inflammatory drugs (NSAIDs), against Gram-negative rods. The activity of eight drugs of potential non-antibiotic activity, active substance standards, and relevant medicinal products were analysed with and without of efflux pump inhibitors against 180 strains of five Gram-negative rod species by minimum inhibitory concentration (MIC) value determination in the presence of 1 mM MgSO4. Furthermore, the influence of non-antibiotics on the susceptibility of clinical strains to quinolones with or without PAβN (Phe-Arg-β-naphthylamide) was investigated. The impacts of PAβN on the susceptibility of bacteria to non-antibiotics suggests that amitriptyline, alendronate, nicergoline, and ticlopidine are substrates of efflux pumps in Gram-negative rods. Amitriptyline/Amitriptylinum showed the highest direct antibacterial activity, with MICs ranging 100–800 mg/L against all studied species. Significant decreases in the MIC values of other active substances (acyclovir, atorvastatin, and famotidine) tested with pump inhibitors were not observed. The investigated non-antibiotic medicinal products did not alter the MICs of quinolones in the absence and in the presence of PAβN to the studied clinical strains of five groups of species.
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219
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Beyond Antimicrobial Resistance: Evidence for a Distinct Role of the AcrD Efflux Pump in Salmonella Biology. mBio 2016; 7:mBio.01916-16. [PMID: 27879336 PMCID: PMC5120143 DOI: 10.1128/mbio.01916-16] [Citation(s) in RCA: 30] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022] Open
Abstract
For over 20 years, bacterial multidrug resistance (MDR) efflux pumps have been studied because of their impact on resistance to antimicrobials. However, critical questions remain, including why produce efflux pumps under non-antimicrobial treatment conditions, and why have multiple pumps if their only purpose is antimicrobial efflux? Salmonella spp. possess five efflux pump families, including the resistance-nodulation-division (RND) efflux pumps. Notably, the RND efflux pump AcrD has a unique substrate profile, distinct from other Salmonella efflux pumps. Here we show that inactivation of acrD results in a profoundly altered transcriptome and modulation of pathways integral to Salmonella biology. The most significant transcriptome changes were central metabolism related, with additional changes observed in pathogenicity, environmental sensing, and stress response pathway expression. The extent of tricarboxylic acid cycle and fumarate metabolism expression changes led us to hypothesize that acrD inactivation may result in motility defects due to perturbation of metabolite concentrations, such as fumarate, for which a role in motility has been established. Despite minimal detectable changes in flagellar gene expression, we found that an acrD mutant Salmonella enterica serovar Typhimurium isolate was significantly impaired for swarming motility, which was restored by addition of fumarate. The acrD mutant outcompeted the wild type in fitness experiments. The results of these diverse experiments provide strong evidence that the AcrD efflux pump is not simply a redundant system providing response resilience, but also has distinct physiological functions. Together, these data indicate that the AcrD efflux pump has a significant and previously underappreciated impact on bacterial biology, despite only minor perturbations of antibiotic resistance profiles. Efflux pumps in Gram-negative bacteria are studied because of their important contributions to antimicrobial resistance. However, the role of these pumps in bacterial biology has remained surprisingly elusive. Here, we provide evidence that loss of the AcrD efflux pump significantly impacts the physiology of Salmonella enterica serovar Typhimurium. Inactivation of acrD led to changes in the expression of 403 genes involved in fundamental processes, including basic metabolism, virulence, and stress responses. Pathways such as these allow Salmonella to grow, survive in the environment, and cause disease. Indeed, our data show that the acrD mutant is more fit than wild-type Salmonella under standard lab conditions. We hypothesized that inactivation of acrD would alter levels of bacterial metabolites, impacting traits such as swarming motility. We demonstrated this by exogenous addition of the metabolite fumarate, which partially restored the acrD mutant’s swarming defect. This work extends our understanding of the role of bacterial efflux pumps.
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220
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Li Y, Cao S, Zhang L, Lau GW, Wen Y, Wu R, Zhao Q, Huang X, Yan Q, Huang Y, Wen X. A TolC-Like Protein of Actinobacillus pleuropneumoniae Is Involved in Antibiotic Resistance and Biofilm Formation. Front Microbiol 2016; 7:1618. [PMID: 27822201 PMCID: PMC5075564 DOI: 10.3389/fmicb.2016.01618] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2016] [Accepted: 09/28/2016] [Indexed: 11/13/2022] Open
Abstract
Actinobacillus pleuropneumoniae is the etiologic agent of porcine contagious pleuropneumonia, a significant disease that causes serious economic losses to the swine industry worldwide. Persistent infections caused by bacterial biofilms are recalcitrant to treat because of the particular drug resistance of biofilm-dwelling cells. TolC, a key component of multidrug efflux pumps, are responsible for multidrug resistance (MDR) in many Gram-negative bacteria. In this study, we identified two TolC-like proteins, TolC1 and TolC2, in A. pleuropneumoniae. Deletion of tolC1, but not tolC2, caused a significant reduction in biofilm formation, as well as increased drug sensitivity of both planktonic and biofilm cells. The genetic-complementation of the tolC1 mutation restored the competent biofilm and drug resistance. Besides, biofilm formation was inhibited and drug sensitivity was increased by the addition of phenylalanine-arginine beta-naphthylamide (PAβN), a well-known efflux pump inhibitor (EPI), suggesting a role for EPI in antibacterial strategies toward drug tolerance of A. pleuropneumoniae. Taken together, TolC1 is required for biofilm formation and is a part of the MDR machinery of both planktonic and biofilm cells, which could supplement therapeutic strategies for resistant bacteria and biofilm-related infections of A. pleuropneumoniae clinical isolate SC1516.
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Affiliation(s)
- Ying Li
- Research Center of Swine Diseases, College of Veterinary Medicine, Sichuan Agricultural University Chengdu, China
| | - Sanjie Cao
- Research Center of Swine Diseases, College of Veterinary Medicine, Sichuan Agricultural University Chengdu, China
| | - Luhua Zhang
- Research Center of Swine Diseases, College of Veterinary Medicine, Sichuan Agricultural UniversityChengdu, China; Department of Pathobiology, University of Illinois at Urbana-ChampaignUrbana, IL, USA
| | - Gee W Lau
- Department of Pathobiology, University of Illinois at Urbana-Champaign Urbana, IL, USA
| | - Yiping Wen
- Research Center of Swine Diseases, College of Veterinary Medicine, Sichuan Agricultural University Chengdu, China
| | - Rui Wu
- Research Center of Swine Diseases, College of Veterinary Medicine, Sichuan Agricultural University Chengdu, China
| | - Qin Zhao
- Research Center of Swine Diseases, College of Veterinary Medicine, Sichuan Agricultural University Chengdu, China
| | - Xiaobo Huang
- Research Center of Swine Diseases, College of Veterinary Medicine, Sichuan Agricultural University Chengdu, China
| | - Qigui Yan
- Research Center of Swine Diseases, College of Veterinary Medicine, Sichuan Agricultural University Chengdu, China
| | - Yong Huang
- Research Center of Swine Diseases, College of Veterinary Medicine, Sichuan Agricultural University Chengdu, China
| | - Xintian Wen
- Research Center of Swine Diseases, College of Veterinary Medicine, Sichuan Agricultural University Chengdu, China
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221
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Fyfe C, Grossman TH, Kerstein K, Sutcliffe J. Resistance to Macrolide Antibiotics in Public Health Pathogens. Cold Spring Harb Perspect Med 2016; 6:a025395. [PMID: 27527699 PMCID: PMC5046686 DOI: 10.1101/cshperspect.a025395] [Citation(s) in RCA: 115] [Impact Index Per Article: 14.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Macrolide resistance mechanisms can be target-based with a change in a 23S ribosomal RNA (rRNA) residue or a mutation in ribosomal protein L4 or L22 affecting the ribosome's interaction with the antibiotic. Alternatively, mono- or dimethylation of A2058 in domain V of the 23S rRNA by an acquired rRNA methyltransferase, the product of an erm (erythromycin ribosome methylation) gene, can interfere with antibiotic binding. Acquired genes encoding efflux pumps, most predominantly mef(A) + msr(D) in pneumococci/streptococci and msr(A/B) in staphylococci, also mediate resistance. Drug-inactivating mechanisms include phosphorylation of the 2'-hydroxyl of the amino sugar found at position C5 by phosphotransferases and hydrolysis of the macrocyclic lactone by esterases. These acquired genes are regulated by either translation or transcription attenuation, largely because cells are less fit when these genes, especially the rRNA methyltransferases, are highly induced or constitutively expressed. The induction of gene expression is cleverly tied to the mechanism of action of macrolides, relying on antibiotic-bound ribosomes stalled at specific sequences of nascent polypeptides to promote transcription or translation of downstream sequences.
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Affiliation(s)
- Corey Fyfe
- Tetraphase Pharmaceuticals, Watertown, Massachusetts 02472
| | | | - Kathy Kerstein
- Tetraphase Pharmaceuticals, Watertown, Massachusetts 02472
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222
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Emergence of a Potent Multidrug Efflux Pump Variant That Enhances Campylobacter Resistance to Multiple Antibiotics. mBio 2016; 7:mBio.01543-16. [PMID: 27651364 PMCID: PMC5030363 DOI: 10.1128/mbio.01543-16] [Citation(s) in RCA: 80] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
UNLABELLED Bacterial antibiotic efflux pumps are key players in antibiotic resistance. Although their role in conferring multidrug resistance is well documented, the emergence of "super" efflux pump variants that enhance bacterial resistance to multiple drugs has not been reported. Here, we describe the emergence of a resistance-enhancing variant (named RE-CmeABC) of the predominant efflux pump CmeABC in Campylobacter, a major zoonotic pathogen whose resistance to antibiotics is considered a serious antibiotic resistance threat in the United States. Compared to the previously characterized CmeABC transporters, RE-CmeABC is much more potent in conferring Campylobacter resistance to antibiotics, which was shown by increased MICs and reduced intracellular accumulation of antibiotics. Structural modeling suggests that sequence variations in the drug-binding pocket of CmeB possibly contribute to the enhanced efflux function. Additionally, RE-CmeABC expands the mutant selection window of ciprofloxacin, enhances the emergence of antibiotic-resistant mutants, and confers exceedingly high-level resistance to fluoroquinolones, an important class of antibiotics for clinical therapy of campylobacteriosis. Furthermore, RE-CmeABC is horizontally transferable, shifts antibiotic MIC distribution among clinical isolates, and is increasingly prevalent in Campylobacter jejuni isolates, suggesting that it confers a fitness advantage under antimicrobial selection. These findings reveal a new mechanism for enhanced multidrug resistance and an effective strategy utilized by bacteria for adaptation to selection from multiple antibiotics. IMPORTANCE Bacterial antibiotic efflux pumps are ubiquitously present in bacterial organisms and protect bacteria from the antibacterial effects of antimicrobials and other toxic compounds by extruding them out of cells. Thus, these efflux transporters represent an important mechanism for antibiotic resistance. In this study, we discovered the emergence and increasing prevalence of a unique efflux pump variant that is much more powerful in the efflux of antibiotics and confers multidrug resistance in Campylobacter, which is a major foodborne pathogen transmitted to humans via the food chain. Unlike other specific resistance determinants that only allow bacteria to resist a particular antimicrobial, the acquisition of a functionally enhanced efflux pump will empower bacteria with simultaneous resistance to multiple classes of antibiotics. These findings reveal a previously undescribed mechanism for enhanced multidrug resistance and open a new direction for us to understand how bacteria adapt to antibiotic treatment.
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223
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Saleem HGM, Seers CA, Sabri AN, Reynolds EC. Dental plaque bacteria with reduced susceptibility to chlorhexidine are multidrug resistant. BMC Microbiol 2016; 16:214. [PMID: 27629863 PMCID: PMC5024456 DOI: 10.1186/s12866-016-0833-1] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2015] [Accepted: 06/16/2016] [Indexed: 10/30/2022] Open
Abstract
BACKGROUND Chlorhexidine (CHX) is used in oral care products to help control dental plaque. In this study dental plaque bacteria were grown on media containing 2 μg/ml chlorhexidine gluconate to screen for bacteria with reduced CHX susceptibility. The isolates were characterized by 16S rRNA gene sequencing and antibiotic resistance profiles were determined using the disc diffusion method. RESULTS The isolates were variably resistant to multiple drugs including ampicillin, kanamycin, gentamicin and tetracycline. Two species, Chryseobacterium culicis and Chryseobacterium indologenes were able to grow planktonically and form biofilms in the presence of 32 μg/ml CHX. In the CHX and multidrug resistant C. indologenes we demonstrated a 19-fold up-regulation of expression of the HlyD-like periplasmic adaptor protein of a tripartite efflux pump upon exposure to 16 μg/ml CHX suggesting that multidrug resistance may be mediated by this system. Exposure of biofilms of these resistant species to undiluted commercial CHX mouthwash for intervals from 5 to 60 s indicated that the mouthwash was unlikely to eliminate them from dental plaque in vivo. CONCLUSIONS The study highlights the requirement for increased vigilance of the presence of multidrug resistant bacteria in dental plaque and raises a potential risk of long-term use of oral care products containing antimicrobial agents for the control of dental plaque.
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Affiliation(s)
- Hafiz Ghulam Murtaza Saleem
- Department of Microbiology and Molecular Genetics, University of the Punjab Quaid-e-Azam Campus, Lahore, Pakistan.,Oral Health Cooperative Research Centre, Melbourne Dental School, and The Bio21 Institute, The University of Melbourne, Melbourne, VIC, 3010, Australia
| | - Christine Ann Seers
- Oral Health Cooperative Research Centre, Melbourne Dental School, and The Bio21 Institute, The University of Melbourne, Melbourne, VIC, 3010, Australia
| | - Anjum Nasim Sabri
- Department of Microbiology and Molecular Genetics, University of the Punjab Quaid-e-Azam Campus, Lahore, Pakistan
| | - Eric Charles Reynolds
- Oral Health Cooperative Research Centre, Melbourne Dental School, and The Bio21 Institute, The University of Melbourne, Melbourne, VIC, 3010, Australia.
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224
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Sequence-Specific Targeting of Bacterial Resistance Genes Increases Antibiotic Efficacy. PLoS Biol 2016; 14:e1002552. [PMID: 27631336 PMCID: PMC5025249 DOI: 10.1371/journal.pbio.1002552] [Citation(s) in RCA: 56] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2016] [Accepted: 08/16/2016] [Indexed: 12/20/2022] Open
Abstract
The lack of effective and well-tolerated therapies against antibiotic-resistant bacteria is a global public health problem leading to prolonged treatment and increased mortality. To improve the efficacy of existing antibiotic compounds, we introduce a new method for strategically inducing antibiotic hypersensitivity in pathogenic bacteria. Following the systematic verification that the AcrAB-TolC efflux system is one of the major determinants of the intrinsic antibiotic resistance levels in Escherichia coli, we have developed a short antisense oligomer designed to inhibit the expression of acrA and increase antibiotic susceptibility in E. coli. By employing this strategy, we can inhibit E. coli growth using 2- to 40-fold lower antibiotic doses, depending on the antibiotic compound utilized. The sensitizing effect of the antisense oligomer is highly specific to the targeted gene's sequence, which is conserved in several bacterial genera, and the oligomer does not have any detectable toxicity against human cells. Finally, we demonstrate that antisense oligomers improve the efficacy of antibiotic combinations, allowing the combined use of even antagonistic antibiotic pairs that are typically not favored due to their reduced activities.
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225
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Abstract
Bacterial multidrug resistance (MDR) efflux pumps are an important mechanism of antibiotic resistance and are required for many pathogens to cause infection. They are also being harnessed to improve microbial biotechnological processes, including biofuel production. Therefore, scientists of many specialties must be able to accurately measure efflux activity. However, myriad methodologies have been described and the most appropriate method is not always clear. Within the scientific literature, many methods are misused or data arising are misinterpreted. The methods for measuring efflux activity can be split into two groups, (i) those that directly measure efflux and (ii) those that measure the intracellular accumulation of a substrate, which is then used to infer efflux activity. Here, we review the methods for measuring efflux and explore the most recent advances in this field, including single-cell or cell-free technologies and mass spectrometry, that are being used to provide more detailed information about efflux pump activity.
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226
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Hernando-Amado S, Blanco P, Alcalde-Rico M, Corona F, Reales-Calderón JA, Sánchez MB, Martínez JL. Multidrug efflux pumps as main players in intrinsic and acquired resistance to antimicrobials. Drug Resist Updat 2016; 28:13-27. [PMID: 27620952 DOI: 10.1016/j.drup.2016.06.007] [Citation(s) in RCA: 103] [Impact Index Per Article: 12.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/18/2016] [Revised: 05/31/2016] [Accepted: 06/23/2016] [Indexed: 12/31/2022]
Abstract
Multidrug efflux pumps constitute a group of transporters that are ubiquitously found in any organism. In addition to other functions with relevance for the cell physiology, efflux pumps contribute to the resistance to compounds used for treating different diseases, including resistance to anticancer drugs, antibiotics or antifungal compounds. In the case of antimicrobials, efflux pumps are major players in both intrinsic and acquired resistance to drugs currently in use for the treatment of infectious diseases. One important aspect not fully explored of efflux pumps consists on the identification of effectors able to induce their expression. Indeed, whereas the analysis of clinical isolates have shown that mutants overexpressing these resistance elements are frequently found, less is known on the conditions that may trigger expression of efflux pumps, hence leading to transient induction of resistance in vivo, a situation that is barely detectable using classical susceptibility tests. In the current article we review the structure and mechanisms of regulation of the expression of bacterial and fungal efflux pumps, with a particular focus in those for which a role in clinically relevant resistance has been reported.
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Affiliation(s)
- Sara Hernando-Amado
- Departamento de Biotecnología Microbiana, Centro Nacional de Biotecnología, CSIC, Darwin 3, Cantoblanco, 28049 Madrid, Spain
| | - Paula Blanco
- Departamento de Biotecnología Microbiana, Centro Nacional de Biotecnología, CSIC, Darwin 3, Cantoblanco, 28049 Madrid, Spain
| | - Manuel Alcalde-Rico
- Departamento de Biotecnología Microbiana, Centro Nacional de Biotecnología, CSIC, Darwin 3, Cantoblanco, 28049 Madrid, Spain
| | - Fernando Corona
- Departamento de Biotecnología Microbiana, Centro Nacional de Biotecnología, CSIC, Darwin 3, Cantoblanco, 28049 Madrid, Spain
| | - Jose A Reales-Calderón
- Departamento de Biotecnología Microbiana, Centro Nacional de Biotecnología, CSIC, Darwin 3, Cantoblanco, 28049 Madrid, Spain
| | - María B Sánchez
- Departamento de Biotecnología Microbiana, Centro Nacional de Biotecnología, CSIC, Darwin 3, Cantoblanco, 28049 Madrid, Spain
| | - José L Martínez
- Departamento de Biotecnología Microbiana, Centro Nacional de Biotecnología, CSIC, Darwin 3, Cantoblanco, 28049 Madrid, Spain.
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227
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Bailey SF, Bataillon T. Can the experimental evolution programme help us elucidate the genetic basis of adaptation in nature? Mol Ecol 2016; 25:203-18. [PMID: 26346808 PMCID: PMC5019151 DOI: 10.1111/mec.13378] [Citation(s) in RCA: 58] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2015] [Revised: 08/26/2015] [Accepted: 09/04/2015] [Indexed: 02/04/2023]
Abstract
There have been a variety of approaches taken to try to characterize and identify the genetic basis of adaptation in nature, spanning theoretical models, experimental evolution studies and direct tests of natural populations. Theoretical models can provide formalized and detailed hypotheses regarding evolutionary processes and patterns, from which experimental evolution studies can then provide important proofs of concepts and characterize what is biologically reasonable. Genetic and genomic data from natural populations then allow for the identification of the particular factors that have and continue to play an important role in shaping adaptive evolution in the natural world. Further to this, experimental evolution studies allow for tests of theories that may be difficult or impossible to test in natural populations for logistical and methodological reasons and can even generate new insights, suggesting further refinement of existing theories. However, as experimental evolution studies often take place in a very particular set of controlled conditions--that is simple environments, a small range of usually asexual species, relatively short timescales--the question remains as to how applicable these experimental results are to natural populations. In this review, we discuss important insights coming from experimental evolution, focusing on four key topics tied to the evolutionary genetics of adaptation, and within those topics, we discuss the extent to which the experimental work compliments and informs natural population studies. We finish by making suggestions for future work in particular a need for natural population genomic time series data, as well as the necessity for studies that combine both experimental evolution and natural population approaches.
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Affiliation(s)
- Susan F. Bailey
- Bioinformatics Research CentreAarhus UniversityC.F. Møllers Allé 8DK‐8000Aarhus CDenmark
| | - Thomas Bataillon
- Bioinformatics Research CentreAarhus UniversityC.F. Møllers Allé 8DK‐8000Aarhus CDenmark
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228
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Klahn P, Brönstrup M. New Structural Templates for Clinically Validated and Novel Targets in Antimicrobial Drug Research and Development. Curr Top Microbiol Immunol 2016; 398:365-417. [PMID: 27704270 DOI: 10.1007/82_2016_501] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
Abstract
The development of bacterial resistance against current antibiotic drugs necessitates a continuous renewal of the arsenal of efficacious drugs. This imperative has not been met by the output of antibiotic research and development of the past decades for various reasons, including the declining efforts of large pharma companies in this area. Moreover, the majority of novel antibiotics are chemical derivatives of existing structures that represent mostly step innovations, implying that the available chemical space may be exhausted. This review negates this impression by showcasing recent achievements in lead finding and optimization of antibiotics that have novel or unexplored chemical structures. Not surprisingly, many of the novel structural templates like teixobactins, lysocin, griselimycin, or the albicidin/cystobactamid pair were discovered from natural sources. Additional compounds were obtained from the screening of synthetic libraries and chemical synthesis, including the gyrase-inhibiting NTBI's and spiropyrimidinetrione, the tarocin and targocil inhibitors of wall teichoic acid synthesis, or the boronates and diazabicyclo[3.2.1]octane as novel β-lactamase inhibitors. A motif that is common to most clinically validated antibiotics is that they address hotspots in complex biosynthetic machineries, whose functioning is essential for the bacterial cell. Therefore, an introduction to the biological targets-cell wall synthesis, topoisomerases, the DNA sliding clamp, and membrane-bound electron transport-is given for each of the leads presented here.
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Affiliation(s)
- Philipp Klahn
- Department of Chemical Biology, Helmholtz Centre for Infection Research, Inhoffenstrasse 7, 38124, Braunschweig, Germany.
| | - Mark Brönstrup
- Department of Chemical Biology, Helmholtz Centre for Infection Research, Inhoffenstrasse 7, 38124, Braunschweig, Germany.
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229
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Antibiotic resistance breakers: can repurposed drugs fill the antibiotic discovery void? Nat Rev Drug Discov 2015; 14:821-32. [DOI: 10.1038/nrd4675] [Citation(s) in RCA: 227] [Impact Index Per Article: 25.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2022]
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230
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Zhou G, Shi QS, Huang XM, Xie XB. The Three Bacterial Lines of Defense against Antimicrobial Agents. Int J Mol Sci 2015; 16:21711-33. [PMID: 26370986 PMCID: PMC4613276 DOI: 10.3390/ijms160921711] [Citation(s) in RCA: 49] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2015] [Revised: 08/21/2015] [Accepted: 08/31/2015] [Indexed: 01/06/2023] Open
Abstract
Antimicrobial agents target a range of extra- and/or intracellular loci from cytoplasmic wall to membrane, intracellular enzymes and genetic materials. Meanwhile, many resistance mechanisms employed by bacteria to counter antimicrobial agents have been found and reported in the past decades. Based on their spatially distinct sites of action and distribution of location, antimicrobial resistance mechanisms of bacteria were categorized into three groups, coined the three lines of bacterial defense in this review. The first line of defense is biofilms, which can be formed by most bacteria to overcome the action of antimicrobial agents. In addition, some other bacteria employ the second line of defense, the cell wall, cell membrane, and encased efflux pumps. When antimicrobial agents permeate the first two lines of defense and finally reach the cytoplasm, many bacteria will make use of the third line of defense, including alterations of intracellular materials and gene regulation to protect themselves from harm by bactericides. The presented three lines of defense theory will help us to understand the bacterial resistance mechanisms against antimicrobial agents and design efficient strategies to overcome these resistances.
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Affiliation(s)
- Gang Zhou
- Guangdong Institute of Microbiology, Guangzhou 510070, Guangdong, China.
- State Key Laboratory of Applied Microbiology Southern China, Guangzhou 510070, Guangdong, China.
- Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, Guangzhou 510070, Guangdong, China.
| | - Qing-Shan Shi
- Guangdong Institute of Microbiology, Guangzhou 510070, Guangdong, China.
- State Key Laboratory of Applied Microbiology Southern China, Guangzhou 510070, Guangdong, China.
- Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, Guangzhou 510070, Guangdong, China.
| | - Xiao-Mo Huang
- Guangdong Institute of Microbiology, Guangzhou 510070, Guangdong, China.
- State Key Laboratory of Applied Microbiology Southern China, Guangzhou 510070, Guangdong, China.
- Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, Guangzhou 510070, Guangdong, China.
| | - Xiao-Bao Xie
- Guangdong Institute of Microbiology, Guangzhou 510070, Guangdong, China.
- State Key Laboratory of Applied Microbiology Southern China, Guangzhou 510070, Guangdong, China.
- Guangdong Provincial Key Laboratory of Microbial Culture Collection and Application, Guangzhou 510070, Guangdong, China.
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231
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Brugger D, Windisch WM. Environmental responsibilities of livestock feeding using trace mineral supplements. ANIMAL NUTRITION (ZHONGGUO XU MU SHOU YI XUE HUI) 2015; 1:113-118. [PMID: 29767146 PMCID: PMC5945946 DOI: 10.1016/j.aninu.2015.08.005] [Citation(s) in RCA: 37] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Accepted: 08/14/2015] [Indexed: 11/18/2022]
Abstract
Trace elements are essential dietary components for livestock species. However, they also exhibit a strong toxic potential. Therefore, their fluxes through the animal organism are tightly regulated by a complex molecular machinery that controls the rate of absorption from the gut lumen as well as the amount of excretion via faeces, urine and products (e.g., milk) in order to maintain an internal equilibrium. When supplemented in doses above the gross requirement trace elements accumulate in urine and faeces and, hence, manure. Thereby, trace element emissions represent a potential threat to the environment. This fact is of particular importance in regard to the widely distributed feeding practice of pharmacological zinc and copper doses for the purpose of performance enhancement. Adverse environmental effects have been described, like impairment of plant production, accumulation in edible animal products and the water supply chain as well as the correlation between increased trace element loads and antimicrobial resistance. In the light of discussions about reducing the allowed upper limits for trace element loads in feed and manure from livestock production in the European Union excessive dosing needs to be critically reconsidered. Moreover, the precision in trace element feeding has to be increased in order to avoid unnecessary supplementation and, thereby, heavy metal emissions from livestock production.
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Affiliation(s)
- Daniel Brugger
- Chair of Animal Nutrition, TUM School of Life Sciences, Technical University of Munich (TUM), Freising 85354, Germany
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232
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Malloci G, Vargiu AV, Serra G, Bosin A, Ruggerone P, Ceccarelli M. A Database of Force-Field Parameters, Dynamics, and Properties of Antimicrobial Compounds. Molecules 2015; 20:13997-4021. [PMID: 26247924 PMCID: PMC6332394 DOI: 10.3390/molecules200813997] [Citation(s) in RCA: 44] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2015] [Accepted: 07/28/2015] [Indexed: 02/01/2023] Open
Abstract
We present an on-line database of all-atom force-field parameters and molecular properties of compounds with antimicrobial activity (mostly antibiotics and some beta-lactamase inhibitors). For each compound, we provide the General Amber Force Field parameters for the major species at physiological pH, together with an analysis of properties of interest as extracted from µs-long molecular dynamics simulations in explicit water solution. The properties include number and population of structural clusters, molecular flexibility, hydrophobic and hydrophilic molecular surfaces, the statistics of intraand inter-molecular H-bonds, as well as structural and dynamical properties of solvent molecules within first and second solvation shells. In addition, the database contains several key molecular parameters, such as energy of the frontier molecular orbitals, vibrational properties, rotational constants, atomic partial charges and electric dipole moment, computed by Density Functional Theory. The present database (to our knowledge the first extensive one including dynamical properties) is part of a wider project aiming to build-up a database containing structural, physico-chemical and dynamical properties of medicinal compounds using different force-field parameters with increasing level of complexity and reliability. The database is freely accessible at http://www.dsf.unica.it/translocation/db/.
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Affiliation(s)
- Giuliano Malloci
- Dipartimento di Fisica, Università degli studi di Cagliari, Cittadella Universitaria, I-09042 Monserrato (Cagliari), Italy.
| | - Attilio Vittorio Vargiu
- Dipartimento di Fisica, Università degli studi di Cagliari, Cittadella Universitaria, I-09042 Monserrato (Cagliari), Italy.
| | - Giovanni Serra
- Dipartimento di Fisica, Università degli studi di Cagliari, Cittadella Universitaria, I-09042 Monserrato (Cagliari), Italy.
| | - Andrea Bosin
- Dipartimento di Fisica, Università degli studi di Cagliari, Cittadella Universitaria, I-09042 Monserrato (Cagliari), Italy.
| | - Paolo Ruggerone
- Dipartimento di Fisica, Università degli studi di Cagliari, Cittadella Universitaria, I-09042 Monserrato (Cagliari), Italy.
| | - Matteo Ceccarelli
- Dipartimento di Fisica, Università degli studi di Cagliari, Cittadella Universitaria, I-09042 Monserrato (Cagliari), Italy.
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233
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Dreier J, Ruggerone P. Interaction of antibacterial compounds with RND efflux pumps in Pseudomonas aeruginosa. Front Microbiol 2015; 6:660. [PMID: 26217310 PMCID: PMC4495556 DOI: 10.3389/fmicb.2015.00660] [Citation(s) in RCA: 105] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2015] [Accepted: 06/16/2015] [Indexed: 01/14/2023] Open
Abstract
Pseudomonas aeruginosa infections are becoming increasingly difficult to treat due to intrinsic antibiotic resistance and the propensity of this pathogen to accumulate diverse resistance mechanisms. Hyperexpression of efflux pumps of the Resistance-Nodulation-Cell Division (RND)-type multidrug efflux pumps (e.g., MexAB-OprM), chromosomally encoded by mexAB-oprM, mexCD-oprJ, mexEF-oprN, and mexXY (-oprA) is often detected in clinical isolates and contributes to worrying multi-drug resistance phenotypes. Not all antibiotics are affected to the same extent by the aforementioned RND efflux pumps. The impact of efflux on antibiotic activity varies not only between different classes of antibiotics but also between members of the same family of antibiotics. Subtle differences in physicochemical features of compound-pump and compound-solvent interactions largely determine how compounds are affected by efflux activity. The combination of different high-resolution techniques helps to gain insight into the functioning of these molecular machineries. This review discusses substrate recognition patterns based on experimental evidence and computer simulations with a focus on MexB, the pump subunit of the main RND transporter in P. aeruginosa.
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Affiliation(s)
- Jürg Dreier
- Basilea Pharmaceutica International Ltd.,Basel, Switzerland
| | - Paolo Ruggerone
- Dipartimento di Fisica, Università di Cagliari – Cittadella UniversitariaMonserrato, Italy
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234
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Piddock LJV. Teixobactin, the first of a new class of antibiotics discovered by iChip technology? J Antimicrob Chemother 2015; 70:2679-80. [DOI: 10.1093/jac/dkv175] [Citation(s) in RCA: 61] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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235
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Symmons MF, Marshall RL, Bavro VN. Architecture and roles of periplasmic adaptor proteins in tripartite efflux assemblies. Front Microbiol 2015; 6:513. [PMID: 26074901 PMCID: PMC4446572 DOI: 10.3389/fmicb.2015.00513] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2015] [Accepted: 05/08/2015] [Indexed: 12/12/2022] Open
Abstract
Recent years have seen major advances in the structural understanding of the different components of tripartite efflux assemblies, which encompass the multidrug efflux (MDR) pumps and type I secretion systems. The majority of these investigations have focused on the role played by the inner membrane transporters and the outer membrane factor (OMF), leaving the third component of the system – the Periplasmic Adaptor Proteins (PAPs) – relatively understudied. Here we review the current state of knowledge of these versatile proteins which, far from being passive linkers between the OMF and the transporter, emerge as active architects of tripartite assemblies, and play diverse roles in the transport process. Recognition between the PAPs and OMFs is essential for pump assembly and function, and targeting this interaction may provide a novel avenue for combating multidrug resistance. With the recent advances elucidating the drug efflux and energetics of the tripartite assemblies, the understanding of the interaction between the OMFs and PAPs is the last piece remaining in the complete structure of the tripartite pump assembly puzzle.
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Affiliation(s)
- Martyn F Symmons
- Department of Veterinary Medicine, University of Cambridge Cambridge, UK
| | - Robert L Marshall
- Institute of Microbiology and Infection, University of Birmingham Birmingham, UK
| | - Vassiliy N Bavro
- Institute of Microbiology and Infection, University of Birmingham Birmingham, UK
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236
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Friedman M. Antibiotic-resistant bacteria: prevalence in food and inactivation by food-compatible compounds and plant extracts. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2015; 63:3805-3822. [PMID: 25856120 DOI: 10.1021/acs.jafc.5b00778] [Citation(s) in RCA: 69] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
Foodborne antibiotic-resistant pathogenic bacteria such as Campylobacter jejuni, Bacillus cereus, Clostridium perfringens, Escherichia coli, Salmonella enterica, Staphylococcus aureus, Vibrio cholerae, and Vibrio parahemolyticus can adversely affect animal and human health, but a better understanding of the factors involved in their pathogenesis is needed. To help meet this need, this overview surveys and interprets much of our current knowledge of antibiotic (multidrug)-resistant bacteria in the food chain and the implications for microbial food safety and animal and human health. Topics covered include the origin and prevalence of resistant bacteria in the food chain (dairy, meat, poultry, seafood, and herbal products, produce, and eggs), their inactivation by different classes of compounds and plant extracts and by the use of chlorine and physicochemical methods (heat, UV light, pulsed electric fields, and high pressure), the synergistic antimicrobial effects of combinations of natural antimicrobials with medicinal antibiotics, and mechanisms of antimicrobial activities and resistant effects. Possible areas for future research are suggested. Plant-derived and other safe natural antimicrobial compounds have the potential to control the prevalence of both susceptible and resistant pathogens in various environments. The collated information and suggested research will hopefully contribute to a better understanding of approaches that could be used to minimize the presence of resistant pathogens in animal feed and human food, thus reducing adverse effects, improving microbial food safety, and helping to prevent or treat animal and human infections.
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Affiliation(s)
- Mendel Friedman
- Western Regional Research Center, Agricultural Research Service, U.S. Department of Agriculture, Albany, California 94710, United States
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237
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Yamaguchi A, Nakashima R, Sakurai K. Structural basis of RND-type multidrug exporters. Front Microbiol 2015; 6:327. [PMID: 25941524 PMCID: PMC4403515 DOI: 10.3389/fmicb.2015.00327] [Citation(s) in RCA: 111] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2015] [Accepted: 04/01/2015] [Indexed: 12/29/2022] Open
Abstract
Bacterial multidrug exporters are intrinsic membrane transporters that act as cellular self-defense mechanism. The most notable characteristics of multidrug exporters is that they export a wide range of drugs and toxic compounds. The overexpression of these exporters causes multidrug resistance. Multidrug-resistant pathogens have become a serious problem in modern chemotherapy. Over the past decade, investigations into the structure of bacterial multidrug exporters have revealed the multidrug recognition and export mechanisms. In this review, we primarily discuss RND-type multidrug exporters particularly AcrAB-TolC, major drug exporter in Gram-negative bacteria. RND-type drug exporters are tripartite complexes comprising a cell membrane transporter, an outer membrane channel and an adaptor protein. Cell membrane transporters and outer membrane channels are homo-trimers; however, there is no consensus on the number of adaptor proteins in these tripartite complexes. The three monomers of a cell membrane transporter have varying conformations (access, binding, and extrusion) during transport. Drugs are exported following an ordered conformational change in these three monomers, through a functional rotation mechanism coupled with the proton relay cycle in ion pairs, which is driven by proton translocation. Multidrug recognition is based on a multisite drug-binding mechanism, in which two voluminous multidrug-binding pockets in cell membrane exporters recognize a wide range of substrates as a result of permutations at numerous binding sites that are specific for the partial structures of substrate molecules. The voluminous multidrug-binding pocket may have numerous binding sites even for a single substrate, suggesting that substrates may move between binding sites during transport, an idea named as multisite-drug-oscillation hypothesis. This hypothesis is consistent with the apparently broad substrate specificity of cell membrane exporters and their highly efficient ejection of drugs from the cell. Substrates are transported through dual multidrug-binding pockets via the peristaltic motion of the substrate translocation channel. Although there are no clinically available inhibitors of bacterial multidrug exporters, efforts to develop inhibitors based on structural information are underway.
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Affiliation(s)
- Akihito Yamaguchi
- Laboratory of Cell Membrane Structural Biology, Institute of Scientific and Industrial Research, Osaka University Ibaraki, Japan
| | - Ryosuke Nakashima
- Laboratory of Cell Membrane Structural Biology, Institute of Scientific and Industrial Research, Osaka University Ibaraki, Japan
| | - Keisuke Sakurai
- Laboratory of Cell Membrane Structural Biology, Institute of Scientific and Industrial Research, Osaka University Ibaraki, Japan
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238
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Narrow-spectrum inhibitors of Campylobacter jejuni flagellar expression and growth. Antimicrob Agents Chemother 2015; 59:3880-6. [PMID: 25870073 DOI: 10.1128/aac.04926-14] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2014] [Accepted: 04/09/2015] [Indexed: 01/16/2023] Open
Abstract
Campylobacter jejuni is a major cause of food-borne illness due to its ability to reside within the gastrointestinal tracts of chickens. Multiple studies have identified the flagella of C. jejuni as a major determinant of chicken colonization. An inhibitor screen of approximately 147,000 small molecules was performed to identify compounds that are able to inhibit flagellar expression in a reporter strain of C. jejuni. Several compounds that modestly inhibited motility of wild-type C. jejuni in standard assays were identified, as were a number of small molecules that robustly inhibited C. jejuni growth, in vitro. Examination of similar bacterial screens found that many of these small molecules inhibited only the growth of C. jejuni. Follow-up assays demonstrated inhibition of other strains of C. jejuni and Campylobacter coli but no inhibition of the closely related Helicobacter pylori. The compounds were determined to be bacteriostatic and nontoxic to eukaryotic cells. Preliminary results from a day-of-hatch chick model of colonization suggest that at least one of the compounds demonstrates promise for reducing Campylobacter colonization loads in vivo, although further medicinal chemistry may be required to enhance bioavailability.
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239
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Contribution of resistance-nodulation-cell division efflux systems to antibiotic resistance and biofilm formation in Acinetobacter baumannii. mBio 2015; 6:mBio.00309-15. [PMID: 25805730 PMCID: PMC4453527 DOI: 10.1128/mbio.00309-15] [Citation(s) in RCA: 136] [Impact Index Per Article: 15.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Acinetobacter baumannii is a nosocomial pathogen of increasing importance due to its multiple resistance to antibiotics and ability to survive in the hospital environment linked to its capacity to form biofilms. To fully characterize the contribution of AdeABC, AdeFGH, and AdeIJK resistance-nodulation-cell division (RND)-type efflux systems to acquired and intrinsic resistance, we constructed, from an entirely sequenced susceptible A. baumannii strain, a set of isogenic mutants overexpressing each system following introduction of a point mutation in their cognate regulator or a deletion for the pump by allelic replacement. Pairwise comparison of every derivative with the parental strain indicated that AdeABC and AdeFGH are tightly regulated and contribute to acquisition of antibiotic resistance when overproduced. AdeABC had a broad substrate range, including β-lactams, fluoroquinolones, tetracyclines-tigecycline, macrolides-lincosamides, and chloramphenicol, and conferred clinical resistance to aminoglycosides. Importantly, when combined with enzymatic resistance to carbapenems and aminoglycosides, this pump contributed in a synergistic fashion to the level of resistance of the host. In contrast, AdeIJK was expressed constitutively and was responsible for intrinsic resistance to the same major drug classes as AdeABC as well as antifolates and fusidic acid. Surprisingly, overproduction of AdeABC and AdeIJK altered bacterial membrane composition, resulting in decreased biofilm formation but not motility. Natural transformation and plasmid transfer were diminished in recipients overproducing AdeABC. It thus appears that alteration in the expression of efflux systems leads to multiple changes in the relationship between the host and its environment, in addition to antibiotic resistance. Increased expression of chromosomal genes for RND-type efflux systems plays a major role in bacterial multidrug resistance. Acinetobacter baumannii has recently emerged as an important human pathogen responsible for epidemics of hospital-acquired infections. Besides its remarkable ability to horizontally acquire resistance determinants, it has a broad intrinsic resistance due to low membrane permeability, endogenous resistance genes, and antibiotic efflux. The study of isogenic mutants from a susceptible A. baumannii clinical isolate overproducing or deleted for each of the three major RND-type pumps demonstrated their major contribution to intrinsic resistance and to the synergism between overproduction of an efflux system and acquisition of a resistance gene. We have also shown that modulation of expression of the structural genes for the efflux systems results in numerous alterations in membrane-associated cellular functions, in particular, in a decrease in biofilm formation and resistance gene acquisition.
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240
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AcrB drug-binding pocket substitution confers clinically relevant resistance and altered substrate specificity. Proc Natl Acad Sci U S A 2015; 112:3511-6. [PMID: 25737552 DOI: 10.1073/pnas.1419939112] [Citation(s) in RCA: 118] [Impact Index Per Article: 13.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023] Open
Abstract
The incidence of multidrug-resistant bacterial infections is increasing globally and the need to understand the underlying mechanisms is paramount to discover new therapeutics. The efflux pumps of Gram-negative bacteria have a broad substrate range and transport antibiotics out of the bacterium, conferring intrinsic multidrug resistance (MDR). The genomes of pre- and posttherapy MDR clinical isolates of Salmonella Typhimurium from a patient that failed antibacterial therapy and died were sequenced. In the posttherapy isolate we identified a novel G288D substitution in AcrB, the resistance-nodulation division transporter in the AcrAB-TolC tripartite MDR efflux pump system. Computational structural analysis suggested that G288D in AcrB heavily affects the structure, dynamics, and hydration properties of the distal binding pocket altering specificity for antibacterial drugs. Consistent with this hypothesis, recreation of the mutation in standard Escherichia coli and Salmonella strains showed that G288D AcrB altered substrate specificity, conferring decreased susceptibility to the fluoroquinolone antibiotic ciprofloxacin by increased efflux. At the same time, the substitution increased susceptibility to other drugs by decreased efflux. Information about drug transport is vital for the discovery of new antibacterials; the finding that one amino acid change can cause resistance to some drugs, while conferring increased susceptibility to others, could provide a basis for new drug development and treatment strategies.
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241
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Lin X, Lin L, Yao Z, Li W, Sun L, Zhang D, Luo J, Lin W. An integrated quantitative and targeted proteomics reveals fitness mechanisms of Aeromonas hydrophila under oxytetracycline stress. J Proteome Res 2015; 14:1515-25. [PMID: 25621997 DOI: 10.1021/pr501188g] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
To date, above ten thousand tons of antibiotics are used in aquaculture each year that lead to the deterioration of natural resources. However, knowledge is limited on the molecular biological behavior of common aquatic pathogens against antibiotics stress. In this study, proteomics profiles of Aeromonas hydrophila, which were exposed to different levels of oxytetracycline (OXY) stress, were displayed and compared using iTRAQ labeling and SWATH-MS based LC-MS/MS methods. A total 1383 proteins were identified by SWATH-MS method, and 2779 proteins were identified from iTRAQ labeling samples. There are 152 up-regulated and 52 down-regulated proteins overlapped in 5 μg/mL OXY stress and both 83 up- and down-regulated proteins overlapped in 10 μg/mL OXY stress in both methods, respectively. Results show that many protein synthesis and translation related proteins increased, while energy generation related proteins decreased in OXY stress. The varieties of selected proteins involved in both pathways were further validated by sMRM(HR), q-PCR, and enzyme activity assay. Furthermore, the concentrations of NAD+ and NADH were measured to verify the characteristic of energy generation process in OXY stress and OXY resistance strain. We demonstrate that the down-regulation of energy generation related metabolic pathways and up-regulation of translation may play an important role in antibiotics fitness or resistance of aquatic pathogens.
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Affiliation(s)
- Xiangmin Lin
- Fujian Provincial Key Laboratory of Agroecological Processing and Safety Monitoring, School of Life Sciences, Fujian Agriculture and Forestry University , Fuzhou 350002, PR China
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