Characterization of resistance genes to macrolides, lincosamides and streptogramins (MLS) among clinical isolates of Staphylococcus aureus in North Lebanon

Background. – Staphylococcus aureus is one of the most significant pathogens causing significant morbidity and mortality. Moreover, the incidence of MLS-resistant Staphylococcus aureus infections continues to grow globally.Objective. – The aim of this study is to examine the expression of resistance of Staphylococcus aureus (S. aureus) isolates to MLS and the prevalence of genes involved in this resistance by PCR.Methods. – 38 strains of S. aureus MLS-resistant (resistant at least for one macrolide) were isolated in the sector of microbiology at Nini Hospital in North Lebanon. The disk diffusion method was used to determine the phenotype of the MLS resistance. The resistance genes involved were detected by PCR using specific gene primers for ermA, ermB, ermC, msrA, linA, mefA, vat and vgb genes.Results. – A total of 55.3% of the isolates were positive for inducible phenotype (iMLSB), 15.8% for the constitutive phenotype (cMLSB), 23.7% for MSB phenotype and 5.2% for L phenotype. The ermC gene was the most prevalent (52.6%), while ermA, ermB, msrA and linA genes were observed with lower prevalence. However, a combination of several of these genes was detected. The vgb, vat and mefA genes were not detected in any of the clinical isolates.Conclusion. – To our knowledge, this study is the first investigation regarding characterization of MLS resistance genes in clinical isolates of S. aureus in Lebanon. The study revealed a high prevalence of the inducible resistance to lincosamides (iMLSB phenotype) and the most prevalent resistance determinants was ermC