scholarly journals The Asp20-to-Asn Substitution in the Response Regulator AdeR Leads to Enhanced Efflux Activity of AdeB in Acinetobacter baumannii

2015 ◽  
Vol 60 (2) ◽  
pp. 1085-1090 ◽  
Author(s):  
Jennifer Nowak ◽  
Thamarai Schneiders ◽  
Harald Seifert ◽  
Paul G. Higgins
Keyword(s):  
Acinetobacter Baumannii ◽  
Antimicrobial Susceptibility ◽  
Efflux Pump ◽  
Response Regulator ◽  
Two Component System ◽  
Content Type ◽  
Susceptibility Data ◽  
Genes Encoding ◽  
Induced Changes

ABSTRACTOverexpression of the resistance-nodulation-cell division-type efflux pump AdeABC is often associated with multidrug resistance inAcinetobacter baumanniiand has been linked to mutations in the genes encoding the AdeRS two-component system. In a previous study, we reported that the Asp20→Asn amino acid substitution in the response regulator AdeR is associated withadeBoverexpression and reduced susceptibility to the antimicrobials levofloxacin, tigecycline, and trimethoprim-sulfamethoxazole. To further characterize the effect of the Asp20→Asn substitution on antimicrobial susceptibility, the expression of the efflux genesadeB,adeJ, andadeG, and substrate accumulation, four plasmid constructs [containingadeR(Asp20)S,adeR(Asn20)S,adeR(Asp20)SABC, andadeR(Asn20)SABC] were introduced into theadeRSABC-deficientA. baumanniiisolate NIPH 60. NeitheradeRSconstruct induced changes in antimicrobial susceptibility or substrate accumulation from that for the vector-only control. TheadeR(Asp20)SABCtransformant showed reduced susceptibility to 6 antimicrobials and accumulated 12% less ethidium than the control, whereas the Asn20 variant showed reduced susceptibility to 6 of 8 antimicrobial classes tested, and its ethidium accumulation was only 72% of that observed for the vector-only construct.adeBexpression was 7-fold higher in theadeR(Asn20)SABCtransformant than in its Asp20 variant. No changes inadeGoradeJexpression or in acriflavine or rhodamine 6G accumulation were detected. The antimicrobial susceptibility data suggest that AdeRS does not regulate any resistance determinants other than AdeABC. Furthermore, the characterization of the Asp20→Asn20 substitution proves that the reduced antimicrobial susceptibility previously associated with this substitution was indeed caused by enhanced efflux activity of AdeB.

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 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 RND-Type Efflux Pumps in Multidrug-Resistant Clinical Isolates of Acinetobacter baumannii: Major Role for AdeABC Overexpression and AdeRS Mutations

2013 ◽  
Vol 57 (7) ◽  
pp. 2989-2995 ◽  
Author(s):  
Eun-Jeong Yoon ◽  
Patrice Courvalin ◽  
Catherine Grillot-Courvalin
Keyword(s):  
Acinetobacter Baumannii ◽  
Efflux Pump ◽  
Regulatory System ◽  
Multidrug Resistant ◽  
Clinical Isolates ◽  
Clinical Settings ◽  
Two Component System ◽  
Content Type ◽  
High Incidence ◽  
Two Component

ABSTRACTIncreased expression of chromosomal genes for resistance-nodulation-cell division (RND)-type efflux systems plays a major role in the multidrug resistance (MDR) ofAcinetobacter baumannii. However, the relative contributions of the three most prevalent pumps, AdeABC, AdeFGH, and AdeIJK, have not been evaluated in clinical settings. We have screened 14 MDR clinical isolates shown to be distinct on the basis of multilocus sequence typing (MLST) and pulsed-field gel electrophoresis (PFGE) for the presence and overexpression of the three Ade efflux systems and analyzed the sequences of the regulators AdeRS, a two-component system, for AdeABC and AdeL, a LysR-type regulator, for AdeFGH. GeneadeBwas detected in 13 of 14 isolates, andadeGand the intrinsicadeJgene were detected in all strains. Significant overexpression ofadeBwas observed in 10 strains, whereas only 7 had moderately increased levels of expression of AdeFGH, and none overexpressed AdeIJK. Thirteen strains had reduced susceptibility to tigecycline, but there was no correlation between tigecycline MICs and the levels of AdeABC expression, suggesting the presence of other mechanisms for tigecycline resistance. No mutations were found in the highly conserved LysR regulator of the nine strains expressing AdeFGH. In contrast, functional mutations were found in conserved domains of AdeRS in all the strains that overexpressed AdeABC with two mutational hot spots, one in AdeS near histidine 149 suggesting convergent evolution and the other in the DNA binding domain of AdeR compatible with horizontal gene transfer. This report outlines the high incidence of AdeABC efflux pump overexpression in MDRA. baumanniias a result of a variety of single mutations in the corresponding two-component regulatory system.

scholarly journals Identification of the Three Genes Involved in Controlling Production of a Phytotoxin Tropolone in Burkholderia plantarii

2016 ◽  
Vol 198 (11) ◽  
pp. 1604-1609 ◽  
Author(s):  
Shunpei Miwa ◽  
Eri Kihira ◽  
Akinori Yoshioka ◽  
Kaoru Nakasone ◽  
Sho Okamoto ◽  
...  
Keyword(s):  
Signal Transduction ◽  
Response Regulator ◽  
Rice Seedling ◽  
Seedling Blight ◽  
Response Regulators ◽  
Two Component System ◽  
Content Type ◽  
Bacterial Signal Transduction ◽  
Genes Encoding ◽  
Cognate Response Regulator

ABSTRACTTropolone, a phytotoxin produced byBurkholderia plantarii, causes rice seedling blight. To identify genes involved in tropolone synthesis, we systematically constructed mutations in the genes encoding 55 histidine kinases and 72 response regulators. From the resulting defective strains, we isolated three mutants, KE1, KE2, and KE3, in which tropolone production was repressed. The deleted genes of these mutants were namedtroR1,troK, andtroR2, respectively. The mutant strains did not cause rice seedling blight, and complementation experiments indicated that TroR1, TroK, and TroR2 were involved in the synthesis of tropolone inB. plantarii. However, tropolone synthesis was repressed in the TroR1 D52A, TroK H253A, and TroR2 D46A site-directed mutants. These results suggest that the putative sensor kinase (TroK) and two response regulators (TroR1 and TroR2) control the production of tropolone inB. plantarii.IMPORTANCEA two-component system is normally composed of a sensor histidine kinase (HK) and a cognate response regulator (RR) pair. In this study, HK (TroK) and two RRs (TroR1 and TroR2) were found to be involved in controlling tropolone production inB. plantarii. These three genes may be part of a bacterial signal transduction network. Such networks are thought to exist in other bacteria to regulate phytotoxin production, as well as environmental adaptation and signal transduction.

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 Contribution of Efflux Pumps, Porins, and β-Lactamases to Multidrug Resistance in Clinical Isolates of Acinetobacter baumannii

2013 ◽  
Vol 57 (11) ◽  
pp. 5247-5257 ◽  
Author(s):  
C. Rumbo ◽  
E. Gato ◽  
M. López ◽  
C. Ruiz de Alegría ◽  
F. Fernández-Cuenca ◽  
...  
Keyword(s):  
Acinetobacter Baumannii ◽  
Efflux Pump ◽  
Efflux Pumps ◽  
System Level ◽  
Pump Level ◽  
Content Type ◽  
Clinical Strains ◽  
Expression Of Genes ◽  
Genes Encoding ◽  
Resistant Strains

ABSTRACTWe investigated the mechanisms of resistance to carbapenems, aminoglycosides, glycylcyclines, tetracyclines, and quinolones in 90 multiresistant clinical strains ofAcinetobacter baumanniiisolated from two genetically unrelatedA. baumanniiclones: clone PFGE-ROC-1 (53 strains producing the OXA-58 β-lactamase enzyme and 18 strains with the OXA-24 β-lactamase) and clone PFGE-HUI-1 (19 strains susceptible to carbapenems). We used real-time reverse transcriptase PCR to correlate antimicrobial resistance (MICs) with expression of genes encoding chromosomal β-lactamases (AmpC and OXA-51), porins (OmpA, CarO, Omp33, Dcap-like, OprB, Omp25, OprC, OprD, and OmpW), and proteins integral to six efflux systems (AdeABC, AdeIJK, AdeFGH, CraA, AbeM, and AmvA). Overexpression of the AdeABC system (level of expression relative to that byA. baumanniiATCC 17978, 30- to 45-fold) was significantly associated with resistance to tigecycline, minocycline, and gentamicin and other biological functions. However, hyperexpression of the AdeIJK efflux pump (level of expression relative to that byA. baumanniiATCC 17978, 8- to 10-fold) was significantly associated only with resistance to tigecycline and minocycline (to which the TetB efflux system also contributed). TetB and TetA(39) efflux pumps were detected in clinical strains and were associated with resistance to tetracyclines and doxycycline. The absence of the AdeABC system and the lack of expression of other mechanisms suggest that tigecycline-resistant strains of the PFGE-HUI-1 clone may be associated with a novel resistance-nodulation-cell efflux pump (decreased MICs in the presence of the inhibitor Phe-Arg β-naphthylamide dihydrochloride) and the TetA(39) system.

scholarly journals Characterization of RarA, a Novel AraC Family Multidrug Resistance Regulator in Klebsiella pneumoniae

2012 ◽  
Vol 56 (8) ◽  
pp. 4450-4458 ◽  
Author(s):  
Mark Veleba ◽  
Paul G. Higgins ◽  
Gerardo Gonzalez ◽  
Harald Seifert ◽  
Thamarai Schneiders
Keyword(s):  
Multidrug Resistance ◽  
Klebsiella Pneumoniae ◽  
Efflux Pump ◽  
Content Type ◽  
Resistance Phenotype ◽  
Serratia Proteamaculans ◽  
Virulence Potential ◽  
Article Type ◽  
Acrab Efflux Pump

ABSTRACTTranscriptional regulators, such as SoxS, RamA, MarA, and Rob, which upregulate the AcrAB efflux pump, have been shown to be associated with multidrug resistance in clinically relevant Gram-negative bacteria. In addition to the multidrug resistance phenotype, these regulators have also been shown to play a role in the cellular metabolism and possibly the virulence potential of microbial cells. As such, the increased expression of these proteins is likely to cause pleiotropic phenotypes.Klebsiella pneumoniaeis a major nosocomial pathogen which can express the SoxS, MarA, Rob, and RamA proteins, and the accompanying paper shows that the increased transcription oframAis associated with tigecycline resistance (M. Veleba and T. Schneiders, Antimicrob. Agents Chemother. 56:4466–4467, 2012). Bioinformatic analyses of the availableKlebsiellagenome sequences show that an additional AraC-type regulator is encoded chromosomally. In this work, we characterize this novel AraC-type regulator, hereby called RarA (Regulator of antibiotic resistance A), which is encoded inK. pneumoniae,Enterobactersp. 638,Serratia proteamaculans568, andEnterobacter cloacae. We show that the overexpression ofrarAresults in a multidrug resistance phenotype which requires a functional AcrAB efflux pump but is independent of the other AraC regulators. Quantitative real-time PCR experiments show thatrarA(MGH 78578 KPN_02968) and its neighboring efflux pump operonoqxAB(KPN_02969_02970) are consistently upregulated in clinical isolates collected from various geographical locations (Chile, Turkey, and Germany). Our results suggest thatrarAoverexpression upregulates theoqxABefflux pump. Additionally, it appears thatoqxR, encoding a GntR-type regulator adjacent to theoqxABoperon, is able to downregulate the expression of theoqxABefflux pump, where OqxR complementation resulted in reductions to olaquindox MICs.

scholarly journals Intra- and Interspecies Signaling betweenStreptococcus salivarius and Streptococcus pyogenes Mediated by SalA and SalA1 Lantibiotic Peptides

2001 ◽  
Vol 183 (13) ◽  
pp. 3931-3938 ◽  
Author(s):  
M. Upton ◽  
J. R. Tagg ◽  
P. Wescombe ◽  
H. F. Jenkinson
Keyword(s):  
Streptococcus Pyogenes ◽  
Response Regulator ◽  
Genetic Locus ◽  
Two Component System ◽  
Peptide Modification ◽  
Insertional Inactivation ◽  
Two Component ◽  
Genes Encoding ◽  
Dose Dependent

ABSTRACT Streptococcus salivarius 20P3 produces a 22-amino-acid residue lantibiotic, designated salivaricin A (SalA), that inhibits the growth of a range of streptococci, including all strains ofStreptococcus pyogenes. Lantibiotic production is associated with the sal genetic locus comprisingsalA, the lantibiotic structural gene; salBCTXgenes encoding peptide modification and export machinery proteins; andsalYKR genes encoding a putative immunity protein and two-component sensor-regulator system. Insertional inactivation ofsalB in S. salivarius 20P3 resulted in abrogation of SalA peptide production, of immunity to SalA, and ofsalA transcription. Addition of exogenous SalA peptide tosalB mutant cultures induced dose-dependent expression ofsalA mRNA (0.2 kb), demonstrating that SalA production was normally autoregulated. Inactivation of salR encoding the response regulator of the SalKR two-component system led to reduced production of, and immunity to, SalA. The sal genetic locus was also present in S. pyogenes SF370 (M type 1), but because of a deletion across the salBCT genes, the corresponding lantibiotic peptide, designated SalA1, was not produced. However, in S. pyogenes T11 (M type 4) the sallocus gene complement was apparently complete, and active SalA1 peptide was synthesized. Exogenously added SalA1 peptide from S. pyogenes T11 induced salA1 transcription in S. pyogenes SF370 and in an isogenic S. pyogenes T11salB mutant and salA transcription in S. salivarius 20P3 salB. Thus, SalA and SalA1 are examples of streptococcal lantibiotics whose production is autoregulated. These peptides act as intra- and interspecies signaling molecules, modulating lantibiotic production and possibly influencing streptococcal population ecology in the oral cavity.

scholarly journals Target (MexB)- and Efflux-Based Mechanisms Decreasing the Effectiveness of the Efflux Pump Inhibitor D13-9001 in Pseudomonas aeruginosa PAO1: Uncovering a New Role for MexMN-OprM in Efflux of β-Lactams and a Novel Regulatory Circuit (MmnRS) Controlling MexMN Expression

2018 ◽  
Vol 63 (2) ◽  
pp. e01718-18 ◽  
Author(s):  
Srijan Ranjitkar ◽  
Adriana K. Jones ◽  
Mina Mostafavi ◽  
Zachary Zwirko ◽  
Oleg Iartchouk ◽  
...  
Keyword(s):  
Pseudomonas Aeruginosa ◽  
Efflux Pump ◽  
Response Regulator ◽  
Heavy Metal Resistance ◽  
Metal Resistance ◽  
Rna Seq ◽  
Efflux Pump Inhibitor ◽  
Content Type ◽  
Regulatory Circuit ◽  
Outer Membrane Channel

ABSTRACT Efflux pumps contribute to antibiotic resistance in Gram-negative pathogens. Correspondingly, efflux pump inhibitors (EPIs) may reverse this resistance. D13-9001 specifically inhibits MexAB-OprM in Pseudomonas aeruginosa. Mutants with decreased susceptibility to MexAB-OprM inhibition by D13-9001 were identified, and these fell into two categories: those with alterations in the target MexB (F628L and ΔV177) and those with an alteration in a putative sensor kinase of unknown function, PA1438 (L172P). The alterations in MexB were consistent with reported structural studies of the D13-9001 interaction with MexB. The PA1438L172P alteration mediated a >150-fold upregulation of MexMN pump gene expression and a >50-fold upregulation of PA1438 and the neighboring response regulator gene, PA1437. We propose that these be renamed mmnR and mmnS for MexMN regulator and MexMN sensor, respectively. MexMN was shown to partner with the outer membrane channel protein OprM and to pump several β-lactams, monobactams, and tazobactam. Upregulated MexMN functionally replaced MexAB-OprM to efflux these compounds but was insusceptible to inhibition by D13-9001. MmnSL172P also mediated a decrease in susceptibility to imipenem and biapenem that was independent of MexMN-OprM. Expression of oprD, encoding the uptake channel for these compounds, was downregulated, suggesting that this channel is also part of the MmnSR regulon. Transcriptome sequencing (RNA-seq) of cells encoding MmnSL172P revealed, among other things, an interrelationship between the regulation of mexMN and genes involved in heavy metal resistance.

scholarly journals Identification of a Second Two-Component Signal Transduction System That Controls Fosfomycin Tolerance and Glycerol-3-Phosphate Uptake

2014 ◽  
Vol 197 (5) ◽  
pp. 861-871 ◽  
Author(s):  
Kumiko Kurabayashi ◽  
Yuko Hirakawa ◽  
Koichi Tanimoto ◽  
Haruyoshi Tomita ◽  
Hidetada Hirakawa
Keyword(s):  
Phosphate Uptake ◽  
Response Regulator ◽  
Anaerobic Respiration ◽  
Regulatory System ◽  
Carbon Substrate ◽  
Two Component System ◽  
Component System ◽  
Content Type ◽  
Two Component ◽  
Biological Cost

Particular interest in fosfomycin has resurfaced because it is a highly beneficial antibiotic for the treatment of refractory infectious diseases caused by pathogens that are resistant to other commonly used antibiotics. The biological cost to cells of resistance to fosfomycin because of chromosomal mutation is high. We previously found that a bacterial two-component system, CpxAR, induces fosfomycin tolerance in enterohemorrhagicEscherichia coli(EHEC) O157:H7. This mechanism does not rely on irreversible genetic modification and allows EHEC to relieve the fitness burden that results from fosfomycin resistance in the absence of fosfomycin. Here we show that another two-component system, TorSRT, which was originally characterized as a regulatory system for anaerobic respiration utilizing trimethylamine-N-oxide (TMAO), also induces fosfomycin tolerance. Activation of the Tor regulatory pathway by overexpression oftorR, which encodes the response regulator, or addition of TMAO increased fosfomycin tolerance in EHEC. We also show that phosphorylated TorR directly represses the expression ofglpT, a gene that encodes a symporter of fosfomycin and glycerol-3-phosphate, and activation of the TorR protein results in the reduced uptake of fosfomycin by cells. However, cells in which the Tor pathway was activated had an impaired growth phenotype when cultured with glycerol-3-phosphate as a carbon substrate. These observations suggest that the TorSRT pathway is the second two-component system to reversibly control fosfomycin tolerance and glycerol-3-phosphate uptake in EHEC, and this may be beneficial for bacteria by alleviating the biological cost. We expect that this mechanism could be a potential target to enhance the utility of fosfomycin as chemotherapy against multidrug-resistant pathogens.

Sign in / Sign up

Export Citation Format

Share Document