Investigation of macrolide, lincosamide and streptogramin B resistance in staphylococcus aureus strains isolated from clinical samples by phenotypical and genotypical methods

Staphylococcus aureus is one of the most common cause of both community and healthcare-associ- Ated infections. As staphylococci have developed resistance to various antibiotics, initially to penicillins then to methicillin and glycopeptides and have the ability to cause epidemics, they continue to be a major problem from past to present. Methicillin resistance gave rise to the use of alternative antibiotics such as macrolides, however worldwide development of macrolide resistance limited the use of these antibiotics. Macrolide resistance occurs either through target site modification (MLSB phenotype, encoded by erm genes), efflux pumps (MS phenotype, encoded by msrA/B genes) or decreased cell wall permeability. The aim of this study was to investigate the MLSB resistance of clinical S.aureus strains with phenotypic and genotypic methods. A total of 404 S.aureus strains isolated from different clinical samples (50% wound, 15% tracheal aspirate and 35% other samples) of inpatients (93.3%) and outpatients (6.7%) were included in the study. Double disc synergy test (D-test) was used for the phenotypical research and PCR was used for the genotypical research of MLSB resistance of isolates. One hundred fifty eight (39.1 %) of the S.aureus isolates were methicillin-resistant (MRSA), and 246 (60.9%) were methicillin-susceptible (MSSA). By the use of D-test, constitutive (cMLSB) and inducible (iMLSB) clindamycin resistance were detected in 19 and 111 isolates, respectively, while five isolates were MS phenotype and 268 isolates were S phenotype (susceptible to erythromycin and clindamycin). The resistance genes of 136 isolates with MLSB resistance phenotype were determined genotypically and among 111 isolates showing iMLSB phenotype ermA gene was found in 81.9% (83 MRSA, 8 MSSA), ermC gene in 10.8% (7 MRSA, 5 MSSA), msrA gene in 10.8% (11 MRSA, 1 MSSA), msrB gene in 1.8% (2 MRSA) and ermB gene in 0.9% (1 MRSA). Among 19 strains with cMLSB phenotype, ermA was found in 57.9% (10 MRSA, 1 MSSA), ermC in 36.8% (6 MRSA, 1 ...