Abstract

PARDO, Lorena et al. Phenotypic and genotypic characterization of oxacillin-susceptible and mecA positive Staphylococcus aureus strains isolated in Uruguay. Rev. argent. microbiol. [online]. 2022, vol.54, n.4, pp.101-110.  Epub Dec 01, 2022. ISSN 0325-7541.  http://dx.doi.org/10.1016/j.ram.2022.05.004.

The aim of this study was to characterize phenotypically and genotypically 27 mecApositive Staphylococcus aureus strains with oxacillin MICs of ≤2 g/ml by Vitek 2, isolated indifferent regions of Uruguay. Susceptibility to oxacillin and cefoxitin was studied by gradient dif-fusion, disk diffusion to cefoxitin, and Phoenix and MicroScan systems. PBP2a was determined.SCCmec typing was performed and the isolates were compared by PFGE. Twenty-six isolateswere susceptible to oxacillin; one strain was susceptible to cefoxitin by disk diffusion and 3strains by gradient diffusion. Phoenix and MicroScan panels detected methicillin resistance in25 and 27 strains, respectively. Twenty-six strains tested positive for PBP2a. Twenty-six strainscarried SCCmec V and 24 belonged to pulsotype A. One strain carried SCCmec IV and did notbelong to pulsotype A. Cefoxitin disk diffusion test and PBP2a detection correctly identified 26of these 27 strains as MRSA. PFGE results suggest the dissemination of a cluster of MRSA carryingSCCmec V.

Keywords : Oxacillin resistant Staphylococcus aureus; mecA; OS MRSA; Inducible resistance; Heteroresistance; PFGE cluster.

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