Phenotypic and genotypic characterisation of multiple antibiotic-resistant Staphylococcus aureus exposed to subinhibitory levels of oxacillin and levofloxacinReportar como inadecuado




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BMC Microbiology

, 16:170

Applied microbiology

Abstract

BackgroundThe emergence and spread of multidrug resistant methicillin-resistant Staphylococcus aureus MDR-MRSA has serious health consequences in the presence of sub-MIC antibiotics. Therefore, this study was designed to evaluate β-lactamase activity, efflux activity, biofilm formation, and gene expression pattern in Staphylococcus aureus KACC 10778, S. aureus ATCC 15564, and S. aureus CCARM 3080 exposed to sublethal concentrations of levofloxacin and oxacillin.

ResultsThe decreased MICs were observed in S. aureus KACC and S. aureus ATCC when exposed to levofloxacin and oxacillin, while and S. aureus CCARM remained resistance to streptomycin 512 μg-mL in the presence of levofloxacin and imipenem >512 μg-mL in the presence of oxacillin. The considerable increase in extracellular and membrane-bound β-lactamase activities was observed in S. aureus ATCC exposed to oxacillin >26 μmol-min-mL. The antibiotic susceptibility of all strains exposed to EPIs CCCP and PAβN varied depending on the classes of antibiotics. The relative expression levels of adhesion-related genes clfA, clfB, fnbA, fnnB, and icaD, efflux-related genes norB, norC, and qacA-B, and enterotoxin gene sec were increased more than 5-fold in S. aureus CCARM. The eno and qacA-B genes were highly overexpressed by more than 12- and 9-folds, respectively, in S. aureus CCARM exposed to levofloxacin. The antibiotic susceptibility, lactamase activity, biofilm-forming ability, efflux activity, and gene expression pattern varied with the intrinsic antibiotic resistance of S. aureus KACC, S. aureus ATCC, and S. aureus CCARM exposed to levofloxacin and oxacillin.

ConclusionsThis study would provide useful information for better understating of combination therapy related to antibiotic resistance mechanisms and open the door for designing effective antibiotic treatment protocols to prevent excessive use of antibiotics in clinical practice.

KeywordsLactamase Biofilm Efflux pump Antibiotic resistance Staphylococcus aureus Gene expression Levofloxacin Oxacillin Electronic supplementary materialThe online version of this article doi:10.1186-s12866-016-0791-7 contains supplementary material, which is available to authorized users.

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Autor: Ara Jo - Juhee Ahn

Fuente: https://link.springer.com/







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