Staphylococcus aureus entre estudantes de enfermagem saudáveis

Abstract

Staphylococcus aureus (S. aureus) is a pathogen involved in the etiology of hospital and community infections, and is also found in the normal flora of a significant percentage of the general population. Several studies have shown an increase in the isolation of multiple-drug-resistant samples of S. aureus, especially to oxacillin (ORSA). Nursing students may be nasal carriers of multi-resistant strains, which represents a potential risk factor for dissemination. The object of the present study is to identify the prevalence, phenotypic and genotypic profiles of S. aureus samples isolated from the nasal cavities of undergraduate Nursing students. The population consisted of 101 undergraduate Nursing students who had their nasal cavities sampled. Colonies suspected of belonging to S. aureus were subjected to Gram reaction and tube coagulase tests, and then evaluated regarding oxacillin and vancomycin susceptibility through the minimum inhibitory concentration (MIC) test. DNA was extracted through CTAB, and the samples identified as oxacillin-resistant were submitted to a polymerase chain reaction (PCR) to identify the MecA gene, with the ATCC 33591 strain of S. aureus as positive control. Eletrophoresis was performed in agarose gel 1.5% with ethidium bromide. A fragment of 154 base pairs indicates the presence of the MecA gene. The genetic typing of oxacillin-resistant samples was performed using the RW3A primer. Among the 101 assayed students, 91 (90.1%) showed isolates of S. aureus. In eight samples, MIC varied between 4 μg/ml and 256 μg/ml. All samples were sensitive to vancomycin. The presence of the MecA gene was identified in all oxacillin-resistant samples through the MIC method. Of the eight oxicillin-resistant samples, 100% were resistant to penicillin, trimethoprim/sulfamethoxazole and tetracyclin. The genetic typing of all eight oxacillinresistant samples showed greater than 84% similarity for four samples, with two of them being 100%.