Molecular investigation of antibiotic resistance genes in methicillin resistant Staphylococcus aureus isolated from nasal cavity in pediatric service

Abstract

Methicillin-resistant staphylococci may also be resistant to some other antibiotics as well as β-lactams. Co-existence of resistance to methicillin and macrolides was genetically investigated in Staphylococcus aureus. A total of 59 S. aureus strains isolated from nasal cavity of patients hospitalized in the pediatric service were investigated for their susceptibility to oxacillin and erythromycin. In addition, the β-lactams resistance gene (mecA and blaZ), the erythromycin resistance methylase genes (ermA, ermB, and ermC) and macrolide efflux genes msrA were analysed by multiplex PCR. The minimal inhibitory concentration (MIC) values revealed that 98 and 97% of isolates were resistant to oxacillin and erythromycin, respectively. In addition, the frequency of resistant strains for tested genes was 66% (mecA), 100% (blaZ), 15% (ermA), 30% (ermB), 22% (ermC) and 36% (msrA). A high rate of macrolide resistance was determined in methicillin-resistant staphylococci. The erm gene was the most frequently detected. Results of susceptibility testing and the carriage of resistance genes did not match. Thus, polymerase chain reaction (PCR) multiplex identification of antibiotic resistance genes, as a rapid and accurate technique, could be a supplementary method, which can be easily incorporated into the diagnostic molecular microbiology laboratory work flow. Key words: Staphylococcus aureus, multidrug resistance, multiplex polymerase chain reaction (PCR).