Dataset Information

Mutations in nalc gene of Mex AB-OprM efflux pump in carbapenem resistant Pseudomonas aeruginosa isolated from burn wounds in Yazd, Iran.

ABSTRACT: Background and Objectives:Burn wound infections have emerged as an important cause of morbidity and mortality in patients due to prolonged hospital stay. Pseudomonas aeruginosa, is the second cause of bacterial burn wound infections. Resistance mechanisms among P. aeruginosa are intrinsic or acquired. Intrinsic resistance mechanisms among P. aeruginosa isolates are inducible AmpC cephalosporinase, decrease of specific porin OprD, and overexpression of RND efflux pump. The aim of this study was detection of mutations in nalC gene in carbapenem resistant P. aeruginosa isolated from burn wounds. Materials and Methods:In this cross-sectional study, 180 burn-wound specimens were collected. Suspected lactose-negative colonies were identified by conventional biochemical methods. Kirby-Bauer and Etest methods were used for susceptibility testing. PCR and sequencing techniques were used for the detection of nalC mutation. Results:Out of 180 specimens received in the laboratory, 54 of isolates were isolated and identified as P. aeroginosa (30%). Of these isolates 20 (37%) were resistant to at least two carbapenems simultaneously. From these carbapenem resistant isolates, 19 (95%), 14 (70%), 14 (70%), 19 (95%) and 16 (80%) were resistant to imipenem, cefepime, piperacillin, ceftizoxime and gentamicin, respectively. Only 1 (2%) isolate was sensitive to all carbapenems and did not has mutation in nalC gene, 20 (37%) isolates were resistant to at least two carbapenems, and had mutations in nalC gene (Gly71?Glu and Ser209?Arg). Conclusion:As the results showed, mutation in efflux pump was observed in carbapenem resistant isolate and this confirmed that the indiscriminate use of antibiotics for treatment or prophylaxis can increase mutation in efflux pump.

SUBMITTER: Tafti FA

PROVIDER: S-EPMC7163040 | biostudies-literature | 2020 Feb

REPOSITORIES: biostudies-literature

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Mutations in nalc gene of Mex AB-OprM efflux pump in carbapenem resistant Pseudomonas aeruginosa isolated from burn wounds in Yazd, Iran.

Tafti Fatemeh Akhavan FA Eslami Gilda G Zandi Hengameh H Barzegar Kazem K

Iranian journal of microbiology 20200201 1

<h4>Background and objectives</h4>Burn wound infections have emerged as an important cause of morbidity and mortality in patients due to prolonged hospital stay. Pseudomonas aeruginosa, is the second cause of bacterial burn wound infections. Resistance mechanisms among P. aeruginosa are intrinsic or acquired. Intrinsic resistance mechanisms among P. aeruginosa isolates are inducible AmpC cephalosporinase, decrease of specific porin OprD, and overexpression of RND efflux pump ...[more]

PMID: 32322377

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Project description:The integral inner membrane resistance-nodulation-division (RND) components of three-component RND-membrane fusion protein-outer membrane factor multidrug efflux systems define the substrate selectivity of these efflux systems. To gain a better understanding of what regions of these proteins are important for substrate recognition, a plasmid-borne mexB gene encoding the RND component of the MexAB-OprM multidrug efflux system of Pseudomonas aeruginosa was mutagenized in vitro by using hydroxylamine and mutations compromising the MexB contribution to antibiotic resistance identified in a DeltamexB strain. Of 100 mutants that expressed wild-type levels of MexB and showed increased susceptibility to one or more of carbenicillin, chloramphenicol, nalidixic acid, and novobiocin, the mexB genes of a representative 46 were sequenced, and 19 unique single mutations were identified. While the majority of mutations occurred within the large periplasmic loops between transmembrane segment 1 (TMS-1) and TMS-2 and between TMS-7 and TMS-8 of MexB, mutations were seen in the TMSs and in other periplasmic as well as cytoplasmic loops. By threading the MexB amino acid sequence through the crystal structure of the homologous RND transporter from Escherichia coli, AcrB, a three-dimensional model of a MexB trimer was obtained and the mutations were mapped to it. Unexpectedly, most mutations mapped to regions of MexB predicted to be involved in trimerization or interaction with MexA rather than to regions expected to contribute to substrate recognition. Intragenic second-site suppressor mutations that restored the activity of the G220S mutant version of MexB, which was compromised for resistance to all tested MexAB-OprM antimicrobial substrates, were recovered and mapped to the apparently distal portion of MexB that is implicated in OprM interaction. As the G220S mutation likely impacted trimerization, it appears that either proper assembly of the MexB trimer is necessary for OprM interaction or OprM association with an unstable MexB trimer might stabilize it, thereby restoring activity.

Dataset Information

Mutations in nalc gene of Mex AB-OprM efflux pump in carbapenem resistant Pseudomonas aeruginosa isolated from burn wounds in Yazd, Iran.

Publications

Mutations in <i>nalc</i> gene of Mex AB-OprM efflux pump in carbapenem resistant <i>Pseudomonas aeruginosa</i> isolated from burn wounds in Yazd, Iran.

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