Efflux Pump Contribution to Multidrug Resistance in Clinical Isolates of <i>Pseudomonas aeruginosa</i>

Kiser, Tyree H.; Obritsch, Marilee D.; Jung, Rose; MacLaren, Robert; Fish, Douglas N.

doi:10.1592/phco.30.7.632

Cited by 33 publications

(28 citation statements)

References 21 publications

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“…Strain HUMV_026 carried a Thr130Pro substitution. A similar amino acid substitution at the same position (Thr-130Ser) was described before [24] with no significant differences between susceptible and resistant isolates. A frameshift mutation due to an insertion of 12 bp between nucleotides 400 and 401 was also discovered in strain HUMV_026.…”

Section: Resultssupporting

confidence: 63%

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Mechanisms of resistance in clinical isolates of Pseudomonas aeruginosa less susceptible to cefepime than to ceftazidime

Esquisabel

Rodrı́guez

Campo-Sosa

et al. 2011

Clinical Microbiology and Infection

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The MIC of cefepime determined with the MicroScan WalkAway system was ≥2 times higher than that of ceftazidime for 105 clinical isolates of Pseudomonas aeruginosa. This phenotype was confirmed by reference microdilution in 68 (64.8%) isolates, corresponding to 48 different rep-PCR patterns. The PSE-1 blactamase was identified in only 13.2% isolates, while oxacillinases were not identified in any of the 68 isolates. The level of expression of mexB, mexD and mexY was determined by real-time RT-PCR in eight clinical isolates representative of the different clones and patterns of susceptibility to cefepime and ceftazidime and in strain PAO1. All clinical strains overexpressed the mexY gene (18.3- to 152.7-fold in comparison with PAO1), although there was not a linear relationship between MIC of cefepime and level of mexY expression. Five of these strains contained mutations in the regulatory gene mexZ. mexD and mexB were also overexpressed in three and two isolates, respectively. Different mutations were observed in the regulatory genes nalD, mexR, nfxB and nalC. In conclusion, we have documented in our institution a polyclonal spread of P. aeruginosa with higher MICs of cefepime than of ceftazidime, related to overexpression of MexXY-OprM, coincident in some isolates with the production of PSE-1, MexCD-OprJ or MexAB-OprM.

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Section: Resultssupporting

confidence: 63%

“…In MexR, the Val-126Glu substitution was found in seven of the eight strains (Table 1). This previously described mutation [22][23][24] was considered non-significant as it was also observed in susceptible wild-type strains. Strain HUMV_026 carried a Thr130Pro substitution.…”

Section: Resultsmentioning

confidence: 99%

Mechanisms of resistance in clinical isolates of Pseudomonas aeruginosa less susceptible to cefepime than to ceftazidime

Esquisabel

Rodrı́guez

Campo-Sosa

et al. 2011

Clinical Microbiology and Infection

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“…One of the essential factors contributing to resistance is associated with efflux pumps, of which four types, namely MexAB-outer membrane protein (Opr)M, MexEF-OprN, MexCD-OprJ and MexXY-OprM, have been widely studied (2). Kiser et al (3) reported that OprM and a group of efflux regulatory genes or efflux protein (NfxB, MexR and MexZ) contributed to multidrug resistance in clinical P. aeruginosa isolates.…”

Section: Introductionmentioning

confidence: 99%

Berberine inhibits the MexXY‑OprM efflux pump to reverse imipenem resistance in a clinical carbapenem‑resistant Pseudomonas aeruginosa isolate in a planktonic state

Fen

Wang

2017

Exp Ther Med

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Abstract. Pseudomonas (P.) aeruginosa is an ubiquitous and metabolically versatile opportunistic pathogen and may cause various life-threatening diseases. Due to increasing emergence of resistance to carbapenems, novel drugs with improved antibacterial activities compared with those of traditional antibiotics are required. In the present study, berberine (BEB), a natural isoquinoline alkaloid, was used in combination with imipenem (IMP), a commonly-used carbapenem, to investigate their antibacterial activities against a clinical P. aeruginosa isolate PA012 and the potential mechanism. Screening revealed that the minimum inhibitory concentrations (MICs) of BEB and IMP were 512 and 256 µg/ml, respectively. The combination of BEB (1/4 MIC) and IMP (1/8 MIC) exhibited a synergistic effect with a fractional inhibitory concentration index of 0.375. The synergism of BEB and IMP was also demonstrated in a time-kill test and by scanning electron microscopic observation. Treatment with BEB at ¼ MIC in combination with IMP at 1/16, 1/8, 1/4 and ½ MIC revealed a concentration-dependent promoting effect of IMP on the intracellular accumulation of BEB and inhibition of bacterial adhesion. Further analysis of gene expression revealed that BEB (1/4 MIC) combined with IMP (1/8 MIC) decreased MexZ, MexX, MexY and outer membrane protein (Opr)M by 38, 35, 46 and 49% in PA012. In conclusion, these results suggested that IMP had synergistic effects with BEB against the clinical isolate PA012 via inhibition of the MexXY-OprM efflux pump.

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“…azithromycin) (Mulet et al, 2009) and triclosan (Chuanchuen et al, 2001) readily selecting mexCD-oprJ-hyperexpressing mutants resistant to these agents. While this efflux system has been implicated in FQ resistance in clinical isolates (Poole, 2000;Reinhardt et al, 2007;Zhanel et al, 2004), mexCD-oprJ-expressing mutants appear to be rare in a clinical setting (Jeannot et al, 2008;Kiser et al, 2010). Similarly, although MexCDOprJ accommodates cefepime (Masuda et al, 2000) it is seldom linked to resistance to this agent in clinical isolates (Jeannot et al, 2008).…”

Section: Introductionmentioning

confidence: 99%

Functional characterization of the NfxB repressor of the mexCD–oprJ multidrug efflux operon of Pseudomonas aeruginosa

Purssell

Poole

2013

Microbiology

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The mexCD-oprJ multidrug efflux operon of Pseudomonas aeruginosa is regulated by the NfxB repressor. Two forms of NfxB have been reported [Shiba et al. (1995). J Bacteriol 177, 5872) although mutagenesis studies here confirm that the larger protein (199 amino acids, 22.4 kDa) is the functional repressor. NfxB binds upstream of the mexCD-oprJ transcription initiation site to a region containing two inverted repeats, both of which are required for binding. Two-hybrid assays confirmed that NfxB is a multimer, with the C-terminal two-thirds of the repressor required for multimerization. Random mutagenesis identified several mutations within the C-terminal region of NfxB required for multimerization, all of which mapped to a three-helix subdomain of the C-terminal region in a structural model of the repressor, which may thus represent the multimerization domain. These mutations compromised NfxB binding to its target DNA in electromobility shift assays, and their introduction into the chromosome of P. aeruginosa enhanced mexCD-oprJ expression and promoted multidrug resistance, consistent with the functional NfxB repressor being a multimer. Site-directed and spontaneous nfxB mutants showing increased mexCD-oprJ expression and multidrug resistance were also recovered, with mutations mapping to the three-helix subdomain again impacting multimerization and DNA binding. Mutations mapping to the N-terminal helix-turn-helix motif implicated in DNA binding did not impact multimerization although they did render the repressor insoluble and unsuitable for mobility shift assays. Size exclusion column chromatography demonstrated that wild-type NfxB forms tetramers in solution, although a mutant form of the repressor carrying a G192D substitution near the C terminus of the protein and compromised for DNA binding and repressor activity forms dimers. These results suggest that NfxB operates as a tetramer (dimer of dimers) and that the C terminus of the protein serves as a tetramerization domain.

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Efflux Pump Contribution to Multidrug Resistance in Clinical Isolates of Pseudomonas aeruginosa

Cited by 33 publications

References 21 publications

Mechanisms of resistance in clinical isolates of Pseudomonas aeruginosa less susceptible to cefepime than to ceftazidime

Mechanisms of resistance in clinical isolates of Pseudomonas aeruginosa less susceptible to cefepime than to ceftazidime

Berberine inhibits the MexXY‑OprM efflux pump to reverse imipenem resistance in a clinical carbapenem‑resistant Pseudomonas aeruginosa isolate in a planktonic state

Functional characterization of the NfxB repressor of the mexCD–oprJ multidrug efflux operon of Pseudomonas aeruginosa

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