Abstract

SANDREA TOLEDO, Lisette Beatriz; PINA REYES, Eyilde Josefina; PAZ MONTES, América  and  TORRES URDANETA, Elba Luisa. Determination of methicillin and erythromycin resistance of Staphylococcus aureus strains isolated at a hospital in Zulia State. Rev. Soc. Ven. Microbiol. [online]. 2012, vol.32, n.2, pp.88-94. ISSN 1315-2556.

Methicillin resistant Staphylococcus aureus strains (MRSA) are associated to diverse infectious processes and their growing resistance represents a serious public health problem. The objectives of this study were to detect methicillin and erythromycin resistance of 60 MRSA strains phenotypically and genotypically, and confirm methicillin resistance. This last one was confirmed by the minimal inhibitory concentration (MIC) method, screening test, cefoxitin resistance (FOX), PBP2a detection, β-lactamase production, and mecA gene detection (PCR). For erythromycin resistance, the disk diffusion method, MIC, inducible clindamycin resistance (D-test), and ermA, ermB, ermC, and msrA gene detection (PCR) were used The MIC, discard test, FOX, and PBP2a methods showed in each test a sensitivity and predictive value of 100% and 98% respectively. One strain was mecA negative, PBP2a negative, and β-lactamase positive and it was considered “borderline”. Thirty five (58.3%) were erythromycin resistant and showed MS_B (6/17.1%), eML.S_B (25/71.4%) and iML.S_B (4/11.4%); these last ones were D-test positive. ermA gene was the most frequent. The erythromycin resistance found contitutes a serious problem since it is one of the treatment alternatives.

Keywords : Staphylococcus aureus; phenotypic and genotypic; methicillin; erythromycin.

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