scholarly journals Triclosan Can Select for an AdeIJK-Overexpressing Mutant of Acinetobacter baumannii ATCC 17978 That Displays Reduced Susceptibility to Multiple Antibiotics

2014 ◽  
Vol 58 (11) ◽  
pp. 6424-6431 ◽  
Author(s):  
Dinesh M. Fernando ◽  
Wayne Xu ◽  
Peter C. Loewen ◽  
George G. Zhanel ◽  
Ayush Kumar
Keyword(s):  
Acinetobacter Baumannii ◽  
Efflux Pump ◽  
Resistant Mutant ◽  
Dilution Method ◽  
Gene Encoding ◽  
Content Type ◽  
Resistance Nodulation Division ◽  
Triclosan Resistance ◽  
Encoding Genes ◽  
Multiple Antibiotics

ABSTRACTIn order to determine if triclosan can select for mutants ofAcinetobacter baumanniiATCC 17978 that display reduced susceptibilities to antibiotics, we isolated a triclosan-resistant mutant,A. baumanniiAB042, by serial passaging ofA. baumanniiATCC 17978 in growth medium supplemented with triclosan. The antimicrobial susceptibility of AB042 was analyzed by the 2-fold serial dilution method. Expression of five different resistance-nodulation-division (RND) pump-encoding genes (adeB,adeG,adeJ,A1S_2818, andA1S_3217), two outer membrane porin-encoding genes (carOandoprD), and the MATE family pump-encoding geneabeMwas analyzed using quantitative reverse transcriptase (qRT) PCR.A. baumanniiAB042 exhibited elevated resistance to multiple antibiotics, including piperacillin-tazobactam, doxycycline, moxifloxacin, ceftriaxone, cefepime, meropenem, doripenem, ertapenem, ciprofloxacin, aztreonam, tigecycline, and trimethoprim-sulfamethoxazole, in addition to triclosan. Genome sequencing ofA. baumanniiAB042 revealed a116G→V mutation infabI, the gene encoding the target enzyme for triclosan. Expression analysis of efflux pumps showed overexpression of the AdeIJK pump, and sequencing ofadeN, the gene that encodes the repressor of theadeIJKoperon, revealed a 73-bp deletion which would cause a premature termination of translation, resulting in an inactive truncated AdeN protein. This work shows that triclosan can select for mutants ofA. baumanniithat display reduced susceptibilities to multiple antibiotics from chemically distinct classes in addition to triclosan resistance. This multidrug resistance can be explained by the overexpression of the AdeIJK efflux pump.

scholarly journals Triclosan resistance in clinical isolates of Acinetobacter baumannii

2009 ◽  
Vol 58 (8) ◽  
pp. 1086-1091 ◽  
Author(s):  
Yagang Chen ◽  
Borui Pi ◽  
Hua Zhou ◽  
Yunsong Yu ◽  
Lanjuan Li
Keyword(s):  
Acinetobacter Baumannii ◽  
Efflux Pump ◽  
Resistance Mechanism ◽  
Dilution Method ◽  
Agar Dilution Method ◽  
Active Efflux ◽  
Low Level ◽  
High Level ◽  
Resistance Rates ◽  
Triclosan Resistance

The susceptibility to triclosan of 732 clinical Acinetobacter baumannii isolates obtained from 25 hospitals in 16 cities in China from December 2004 to December 2005 was screened by using an agar dilution method. Triclosan MICs ranged between 0.015 and 16 mg l−1, and the MIC90 was 0.5 mg l−1, lower than the actual in-use concentration of triclosan. Twenty triclosan-resistant isolates (MICs ≥1 mg l−1) were characterized by antibiotic susceptibility, clonal relatedness, fabI mutation, fabI expression, and efflux pump phenotype and expression to elucidate the resistance mechanism of A. baumannii to triclosan. The resistance rates of triclosan-resistant isolates to imipenem, levofloxacin, amikacin and tetracycline were higher than those of triclosan-sensitive isolates. Triclosan resistance was artificially classified as low level (MICs 1–2 mg l−1) or high level (MICs ≥4 mg l−1). High-level triclosan resistance could be explained by a Gly95Ser mutation of FabI, whilst wild-type fabI was observed to be overexpressed in low-level resistant isolates. Active efflux did not appear to be a major reason for acquired triclosan resistance, but acquisition of resistance appeared to be dependent on a background of intrinsic triclosan efflux.

scholarly journals Contribution of Resistance-Nodulation-Division Efflux Pump OperonsmeU1-V-W-U2-Xto Multidrug Resistance of Stenotrophomonas maltophilia

2011 ◽  
Vol 55 (12) ◽  
pp. 5826-5833 ◽  
Author(s):  
Chao-Hsien Chen ◽  
Chiang-Ching Huang ◽  
Tsao-Chuen Chung ◽  
Rouh-Mei Hu ◽  
Yi-Wei Huang ◽  
...  
Keyword(s):  
Stenotrophomonas Maltophilia ◽  
Efflux Pump ◽  
Acquired Resistance ◽  
Type Systems ◽  
Resistant Mutant ◽  
Multidrug Resistant ◽  
Content Type ◽  
Membrane Fusion Protein ◽  
Resistance Nodulation Division

ABSTRACTKJ09C, a multidrug-resistant mutant ofStenotrophomonas maltophiliaKJ, was generated byin vitroselection with chloramphenicol. The multidrug-resistant phenotype of KJ09C was attributed to overexpression of a resistance nodulation division (RND)-type efflux system encoded by an operon consisting of five genes:smeU1,smeV,smeW,smeU2, andsmeX. Proteins encoded bysmeV,smeW, andsmeXwere similar to the membrane fusion protein, RND transporter, and outer membrane protein, respectively, of known RND-type systems. The proteins encoded bysmeU1andsmeU2were found to belong to the family of short-chain dehydrogenases/reductases. Mutant KJ09C exhibited increased resistance to chloramphenicol, quinolones, and tetracyclines and susceptibility to aminoglycosides; susceptibility to β-lactams and erythromycin was not affected. The expression of thesmeU1-V-W-U2-Xoperon was regulated by the divergently transcribed LysR-type regulator genesmeRv. Overexpression of the SmeVWX pump contributed to the acquired resistance to chloramphenicol, quinolones, and tetracyclines. Inactivation ofsmeVandsmeWcompletely abolished the activity of the SmeVWX pump, whereas inactivation ofsmeXalone decreased the activity of the SmeVWX pump. The enhanced aminoglycoside susceptibility observed in KJ09C resulted from SmeX overexpression.

scholarly journals Roles of Efflux Pumps from Different Superfamilies in the Surface-Associated Motility and Virulence of Acinetobacter baumannii ATCC 17978

2019 ◽  
Vol 63 (3) ◽  
Author(s):  
María Pérez-Varela ◽  
Jordi Corral ◽  
Jesús Aranda ◽  
Jordi Barbé
Keyword(s):  
Acinetobacter Baumannii ◽  
Efflux Pump ◽  
Efflux Pumps ◽  
Major Facilitator Superfamily ◽  
Content Type ◽  
Small Multidrug Resistance ◽  
Genes Encoding ◽  
Resistance Nodulation Division ◽  
Major Facilitator ◽  
Reported Data

ABSTRACT Although the relationship between Acinetobacter baumannii efflux pumps and antimicrobial resistance is well documented, less is known about the involvement of these proteins in the pathogenicity of this nosocomial pathogen. In previous work, we identified the AbaQ major facilitator superfamily (MFS) efflux pump and demonstrated its participation in the motility and virulence of A. baumannii. In the present study, we examined the role in these processes of A. baumannii transporters belonging to different superfamilies of efflux pumps. Genes encoding known or putative permeases belonging to efflux pump superfamilies other than the MFS were selected, and the corresponding knockouts were constructed. The antimicrobial susceptibilities of these mutants were consistent with previously reported data. In mutants of A. baumannii strain ATCC 17978 carrying inactivated genes encoding the efflux pumps A1S_2736 (resistance nodulation division [RND]), A1S_3371 (multidrug and toxic compound extrusion [MATE]), and A1S_0710 (small multidrug resistance [SMR]), as well as the newly described ATP-binding cassette (ABC) permeases A1S_1242 and A1S_2622, both surface-associated motility and virulence were reduced compared to the parental strain. However, inactivation of the genes encoding the known ABC permeases A1S_0536 and A1S_1535, the newly identified putative ABC permeases A1S_0027 and A1S_1057, or the proteobacterial antimicrobial compound efflux (PACE) transporters A1S_1503 and A1S_2063 had no effects on bacterial motility or virulence. Our results demonstrate the involvement of antimicrobial transporters belonging at least to five of the six known efflux pump superfamilies in both surface-associated motility and virulence in A. baumannii ATCC 17978.

scholarly journals Biofilm Formation Caused by Clinical Acinetobacter baumannii Isolates Is Associated with Overexpression of the AdeFGH Efflux Pump

2015 ◽  
Vol 59 (8) ◽  
pp. 4817-4825 ◽  
Author(s):  
Xinlong He ◽  
Feng Lu ◽  
Fenglai Yuan ◽  
Donglin Jiang ◽  
Peng Zhao ◽  
...  
Keyword(s):  
Acinetobacter Baumannii ◽  
Gene Transcription ◽  
Biofilm Formation ◽  
Efflux Pump ◽  
Outer Membrane Proteins ◽  
Content Type ◽  
Potential Association ◽  
Genes Encoding ◽  
Clinical Environments

ABSTRACTChronic wound infections are associated with biofilm formation, which in turn has been correlated with drug resistance. However, the mechanism by which bacteria form biofilms in clinical environments is not clearly understood. This study was designed to investigate the biofilm formation potency ofAcinetobacter baumanniiand the potential association of biofilm formation with genes encoding efflux pumps, quorum-sensing regulators, and outer membrane proteins. A total of 48 clinically isolatedA. baumanniistrains, identified by enterobacterial repetitive intergenic consensus (ERIC)-PCR as types A-II, A-III, and A-IV, were analyzed. Three representative strains, which were designatedA. baumanniiABR2, ABR11, and ABS17, were used to evaluate antimicrobial susceptibility, biofilm inducibility, and gene transcription (abaI,adeB,adeG,adeJ,carO, andompA). A significant increase in the MICs of different classes of antibiotics was observed in the biofilm cells. The formation of a biofilm was significantly induced in all the representative strains exposed to levofloxacin. The levels of gene transcription varied between bacterial genotypes, antibiotics, and antibiotic concentrations. The upregulation ofadeGcorrelated with biofilm induction. The consistent upregulation ofadeGandabaIwas detected in A-III-typeA. baumanniiin response to levofloxacin and meropenem (1/8 to 1/2× the MIC), conditions which resulted in the greatest extent of biofilm induction. This study demonstrates a potential role of the AdeFGH efflux pump in the synthesis and transport of autoinducer molecules during biofilm formation, suggesting a link between low-dose antimicrobial therapy and a high risk of biofilm infections caused byA. baumannii. This study provides useful information for the development of antibiofilm strategies.

scholarly journals Assessment of Minocycline and Polymyxin B Combination against Acinetobacter baumannii

2015 ◽  
Vol 59 (5) ◽  
pp. 2720-2725 ◽  
Author(s):  
Dana R. Bowers ◽  
Henry Cao ◽  
Jian Zhou ◽  
Kimberly R. Ledesma ◽  
Dongxu Sun ◽  
...  
Keyword(s):  
Acinetobacter Baumannii ◽  
Clinical Utility ◽  
Efflux Pump ◽  
Polymyxin B ◽  
Intracellular Concentration ◽  
Bacterial Cells ◽  
Efflux Pump Inhibitor ◽  
Content Type

ABSTRACTAntimicrobial resistance amongAcinetobacter baumanniiis increasing worldwide, often necessitating combination therapy. The clinical utility of using minocycline with polymyxin B is not well established. In this study, we investigated the activity of minocycline and polymyxin B against 1 laboratory isolate and 3 clinical isolates ofA. baumannii. Minocycline susceptibility testing was performed with and without an efflux pump inhibitor, phenylalanine-arginine β-naphthylamide (PAβN). The intracellular minocycline concentration was determined with and without polymyxin B (0.5 μg/ml). Time-kill studies were performed over 24 h using approximately 106CFU/ml of each strain with clinically relevant minocycline concentrations (2 μg/ml and 8 μg/ml), with and without polymyxin B (0.5 μg/ml). Thein vivoefficacy of the combination was assessed in a neutropenic murine pneumonia model. Infected animals were administered minocycline (50 mg/kg), polymyxin B (10 mg/kg), or both to achieve clinically equivalent exposures in humans. A reduction in the minocycline MIC (≥4×) was observed in the presence of PAβN. The intracellular concentration andin vitrobactericidal effect of minocycline were both enhanced by polymyxin B. With 2 minocycline-susceptible strains, the bacterial burden in lung tissue at 24 h was considerably reduced by the combination compared to monotherapy with minocycline or polymyxin B. In addition, the combination prolonged survival of animals infected with a minocycline-susceptible strain. Polymyxin B increased the intracellular concentration of minocycline in bacterial cells and enhanced the bactericidal activity of minocycline, presumably due to efflux pump disruption. The clinical utility of this combination should be further investigated.

scholarly journals mmpL7 Gene of Mycobacterium tuberculosis Is Responsible for Isoniazid Efflux in Mycobacterium smegmatis

2005 ◽  
Vol 49 (11) ◽  
pp. 4775-4777 ◽  
Author(s):  
Maria R. Pasca ◽  
Paola Guglierame ◽  
Edda De Rossi ◽  
Francesca Zara ◽  
Giovanna Riccardi
Keyword(s):  
Mycobacterium Tuberculosis ◽  
High Resistance ◽  
Mycobacterium Smegmatis ◽  
Efflux Pump ◽  
Gene Encoding ◽  
Resistance Level ◽  
Carbonyl Cyanide ◽  
Resistance Nodulation Division ◽  
Efflux Pump Inhibitors ◽  
Energy Dependent

ABSTRACT The Mycobacterium tuberculosis mmpL7 gene, encoding a hypothetical resistance nodulation division transporter, confers a high resistance level to isoniazid when overexpressed in Mycobacterium smegmatis. The resistance level decreased in the presence of the efflux pump inhibitors reserpine and CCCP (carbonyl cyanide m-chlorophenylhydrazone). Energy-dependent efflux of isoniazid from M. smegmatis cells expressing the mmpL7 gene was observed.

scholarly journals Functional Characterization of AbaQ, a Novel Efflux Pump Mediating Quinolone Resistance inAcinetobacter baumannii

2018 ◽  
Vol 62 (9) ◽  
Author(s):  
María Pérez-Varela ◽  
Jordi Corral ◽  
Jesús Aranda ◽  
Jordi Barbé
Keyword(s):  
Acinetobacter Baumannii ◽  
Antimicrobial Agents ◽  
Efflux Pump ◽  
Functional Characterization ◽  
Multidrug Resistant ◽  
Quinolone Resistance ◽  
Nosocomial Pathogen ◽  
Content Type ◽  
Mfs Transporter

ABSTRACTAcinetobacter baumanniihas emerged as an important multidrug-resistant nosocomial pathogen. In previous work, we identified a putative MFS transporter, AU097_RS17040, involved in the pathogenicity ofA. baumannii(M. Pérez-Varela, J. Corral, J. A. Vallejo, S. Rumbo-Feal, G. Bou, J. Aranda, and J. Barbé, Infect Immun 85:e00327-17, 2017,https://doi.org/10.1128/IAI.00327-17). In this study, we analyzed the susceptibility to diverse antimicrobial agents ofA. baumanniicells defective in this transporter, referred to as AbaQ. Our results showed that AbaQ is mainly involved in the extrusion of quinolone-type drugs inA. baumannii.

scholarly journals Draft Genome Sequence of Ezakiella peruensis Strain M6.X2, a Human Gut Gram-Positive Anaerobic Coccus

2018 ◽  
Vol 6 (9) ◽  
pp. e01487-17
Author(s):  
Awa Diop ◽  
Khoudia Diop ◽  
Enora Tomei ◽  
Didier Raoult ◽  
Florence Fenollar ◽  
...  
Keyword(s):  
Genome Sequence ◽  
Draft Genome ◽  
Antibiotic Resistance Genes ◽  
Draft Genome Sequence ◽  
Human Gut ◽  
Gene Encoding ◽  
Content Type ◽  
Protein Encoding ◽  
Short Palindromic Repeat ◽  
Encoding Genes

ABSTRACT We report here the draft genome sequence of Ezakiella peruensis strain M6.X2T. The draft genome is 1,672,788 bp long and harbors 1,589 predicted protein-encoding genes, including 26 antibiotic resistance genes with 1 gene encoding vancomycin resistance. The genome also exhibits 1 clustered regularly interspaced short palindromic repeat region and 333 genes acquired by horizontal gene transfer.

scholarly journals Aminoglycoside Heteroresistance inAcinetobacter baumanniiAB5075

mSphere ◽  
2018 ◽  
Vol 3 (4) ◽  
Author(s):  
Sarah E. Anderson ◽  
Edgar X. Sherman ◽  
David S. Weiss ◽  
Philip N. Rather
Keyword(s):  
Acinetobacter Baumannii ◽  
Population Analysis ◽  
World Health ◽  
Dependent Manner ◽  
Aminoglycoside Resistance ◽  
Gene Encoding ◽  
Integrase Gene ◽  
Content Type ◽  
Mechanistic Basis ◽  
Health Organization

ABSTRACTHeteroresistance is a phenomenon where a subpopulation of cells exhibits higher levels of antibiotic resistance than the general population. Analysis of tobramycin resistance inAcinetobacter baumanniiAB5075 using Etest strips demonstrated that colonies with increased resistance arose at high frequency within the zone of growth inhibition. The presence of a resistant subpopulation was confirmed by population analysis profiling (PAP). The tobramycin-resistant subpopulation was cross resistant to gentamicin but not amikacin. The increased tobramycin resistance phenotype was highly unstable, and cells reverted to a less resistant population at frequencies of 60 to 90% after growth on nonselective media. Furthermore, the frequency of the resistant subpopulation was not increased by preincubation with subinhibitory concentrations of tobramycin. The tobramycin-resistant subpopulation was shown to replicate during the course of antibiotic treatment, demonstrating that these were not persister cells. InA. baumanniiAB5075, a large plasmid (p1AB5075) carriesaadB, a 2″-nucleotidyltransferase that confers resistance to both tobramycin and gentamicin but not amikacin. TheaadBgene is part of an integron and is carried adjacent to four additional resistance genes that are all flanked by copies of an integrase gene. In isolates with increased resistance, this region was highly amplified in a RecA-dependent manner. However, in arecAmutant, colonies with unstable tobramycin resistance arose by a mechanism that did not involve amplification of this region. These data indicate that tobramycin heteroresistance occurs by at least two mechanisms inA. baumannii, and future studies to determine its effect on patient outcomes are warranted.IMPORTANCEAcinetobacter baumanniihas become an important pathogen in hospitals worldwide, where the incidence of these infections has been increasing.A. baumanniiinfections have become exceedingly difficult to treat due to a rapid increase in the frequency of multidrug- and pan-resistant isolates. This has prompted the World Health Organization to listA. baumanniias the top priority for the research and development of new antibiotics. This study reports for the first time a detailed analysis of aminoglycoside heteroresistance inA. baumannii. We define the mechanistic basis for heteroresistance, where theaadB(ant2″)Iagene encoding an aminoglycoside adenylyltransferase becomes highly amplified in a RecA-dependent manner. Remarkably, this amplification of 20 to 40 copies occurs stochastically in 1/200 cells in the absence of antibiotic selection. In addition, we provide evidence for a second RecA-independent mechanism for aminoglycoside heteroresistance. This study reveals that aminoglycoside resistance inA. baumanniiis far more complex than previously realized and has important implications for the use of aminoglycosides in treatingA. baumanniiinfections.

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