Abstract

One hundred (100) staphylococci were isolated from several Egyptian hospitals and laboratories which include 85 clinical isolates and 15 from hospital surroundings. The isolates were identified by conventional and molecular techniques. Fifty (50) isolates were identified as Staphylococcus aureus (SA), 40 were Staphylococcus epidermidis (SE) while 10 were identified as Staphylococcus species (SS). Upon testing the resistance to methicillin and vancomycin, it was found that resistance is dominant in isolates from clinical samples than those from the surrounding surfaces. Moreover, the resistance to methicillin was higher than that to vancomycin. Multiplex polymerase chain reaction was carried out to characterize the staphylococci-specific region of 16S rRNA gene, mecA gene associated with methicillin resistance and the virulence marker-associated genes Panton-Valentine leukocidin (PVL) lukS/F-PV genes which are responsible for leukocyte destruction and tissue necrosis. All the methicillin resistant staphylococci (MRS) were found to be mecA⁺ while only five MRS carried lukS/F-PV genes. On the other hand, 30% of the methicillin sensitive staphylococci (MSS) were found to harbor the mecA gene while lacking the PVL. The results highlight the important role of horizontal gene transfer of virulence genes between staphylococci. In addition, this study indicates that the use of multiplex PCR is not sufficient for antibiotic susceptibility prediction and thus the simultaneous use of conventional and multiplex PCR technique is required for the identification of staphylococci and determination of their antibiotic susceptibility.

Key words: Methicillin resistance, Staphylococcus aureus, Staphylococcus epidermidis, mecA, Panton-Valentine leukocidin (PVL).