Phenotypic and molecular characterization of resistance to macrolides, lincosamides and type B streptogramin of clinical isolates of Staphylococcus spp. of a university hospital in Recife, Pernambuco, Brazil

INTRODUCTION: There is a mechanism of macrolide resistance in Staphylococcus spp. which also affects the lincosamides and type B streptogramins characterizing the so-called MLS(B) resistance, whose expression can be constitutive (cMLS(B)) or inducible (iMLS(B)) and is encoded mainly by ermA and ermC genes. The cMLS(B) resistance is easily detected by susceptibility testing used in the laboratory routine, but iMLS(B) resistance is not. Therapy with clindamycin in cases of infection with isolated iMLS(B) resistance may fail. OBJECTIVE: To characterize the phenotypic (occurrence of cMLS(B) and iMLS(B) phenotypes) and molecular (occurrence of ermA and ermC genes) profiles of MLS(B) resistance of clinical isolates of susceptible and methicillin-resistant Staphylococcus aureus and CNS (coagulase-negative Staphylococcus) from patients of a university hospital, in Pernambuco. METHODS: The antimicrobial susceptibility of 103 isolates was determined by the disk diffusion technique in Mueller–Hinton agar followed by oxacillin screening. The iMLS(B) phenotype was detected by D test. Isolates with cMLS(B) and iMLS(B) phenotypes were subjected to polymerase chain reaction (PCR) for the detection of ermA and ermC genes. RESULTS: The cMLS(B) and iMLS(B) phenotypes were respectively identified in 39 (37.9%) and five (4.9%) isolates. The iMLS(B) phenotype was found only in four (10.8%) methicillin-susceptible S. aureus and one (4.5%) methicillin-resistant S. aureus. In the 44 isolates subjected to PCR, four (9.1%) only ermA gene was detected, a lower frequency when compared to only ermC 17 (38.6%) gene and to one (2.3%) isolate presenting both genes. CONCLUSION: In the Staphylococcus spp. analyzed, the ermC gene was found more often than the ermA, although the iMLS(B) phenotype had been less frequent than the cMLS(B). It was important to perform the D test for its detection to guide therapeutic approaches.