Phenotypic characterization of macrolide and lincosamide resistance patterns in clinical isolates of staphylococci

Introduction: The macrolide, lincosamides, and streptogramin (MLS) group of antibiotics are one of the few alternative antibiotics available for the treatment of methicillin-resistant staphylococcal isolates. Clinical failures with these antibiotics have been reported because of the usage of these drugs in improperly characterized and tested isolates. The purpose of this study was to know the prevalence of different phenotypes in our area, with an emphasis on inducible resistance detection. Materials and Methods: A total of 100 methicillin-resistant staphylococcal isolates were included in the study. Phenotypic characterization was done by using erythromycin and clindamycin disks kept at a distance of 15 mm on the Muller Hinton agar plate and incubating at 24 h. Results: Among 100 isolates, 23 were sensitive to both erythromycin and clindamycin (S phenotype). Thirty-one isolates were resistant to erythromycin but sensitive to clindamycin (MS phenotype). Inducible resistance (iMLS B ) was seen in 26 of the total isolates. Isolates which were resistant to both the antibiotics numbered 19 (cMLS B ). There was only one isolate which was sensitive to erythromycin but resistant to clindamycin (L phenotype). Conclusion: MLS group of antibiotics is still an effective group of antibiotics against methicillin-resistant staphylococcal isolates, and routine testing for the inducible resistance in these isolates will help in the prevention of therapeutic failure and for the better management of the patient.