Detection of disinfectant and antibiotic resistance genes in Staphylococcus aureus isolated from the oral cavity of Tunisian children

Abstract

Staphylococcus aureus is an important pathogen associated to dental infection. Many antiseptic agents are used in hygienic handwash to prevent nosocomial infections by methicillin-resistant staphylococci. In this study, 22 Staphylococcus aureus strains isolated from the oral cavity of Tunisian children were investigated for their susceptibility to benzalkonium chloride (0.5-512 μg/ml) and antibiotics. The β-lactams resistance gene blaZ, the erythromycin resistance methylase genes (ermA, ermB and ermC), the macrolide efflux gene (msrA) and the disinfectant resistance genes (qacH, qacA, qacB and qacC) were also investigated. Determination of the minimal inhibitory concentration values revealed that 54.5, 54.5, 68, and 82% of isolates were resistant to benzalkonium chloride, oxacillin, tetracycline and erythromycin respectively. The frequency of strains positive for the antibiotic resistance genes tested was 100 (blaZ), 50 (ermA), 36.4 (ermB), 22.7 (ermC) and 13.6% (mrsA). The qacH and the qacA genes were found in 22.7% of isolates and qacB and qacC in 13.6%. Two strains harboured three qac (qacH, qacA and qacB or qacC) genes. These data highlight the importance of determining the susceptibility to antibiotics and disinfectants of strains isolated in dental medicine in order to monitor the epidemiology and spread of multi-drug resistant staphylococci. © Springer-Verlag and the University of Milan 2011.