Identification of inducible clindamycin resistance in Staphylococcus areus methicillin resistance from clinical isolates by D-zone test

Introduction& The increasing incidence of infections caused by strains of Staphylococcus aureus، especially methicillin-resistant (MRSA)، the use of effective antibiotics such as clindamycin and erythromycin has increased for treatment of systemic and local infections caused by this organism. However، concern over the possibility of emergence of clindamycin resistance during therapy has discouraged some clinicians from prescribing that agent. The aim of this study was to identify the induced clindamycin resistance in clinical isolates of methicillin-resistant Staphylococcus aureus. In this cross-sectional study 100 S. aureus strains isolated from clinical specimens were collected from laboratories of Shiraze (Shahid Faghihi، Namazi and MRI) hospitals. Re-identification of isolates was performed by conventional microbiological and biochemical testes. Methicillin resistant strains were selected by disc diffusion method and inducible clindamycin resistances in these strains were identified with D-zone Test. The susceptibility testing result showed that 44 isolates (44%) of 100 Staphylococcus aureus samples، were resistant to methicillin. Forty-six percent of isolates were resistant to erythromycin and 51% were resistant to clindamycin. Ten isolates (10%) were as induced clindamycin resistances based on D-zone test (8 isolates D phenotype، 2 isolates D+ phenotype)، in those 8 isolates were MRSA and 2 isolates were MSSA. The results showed that performance of D-zone test in clinical laboratories for identification of induced clindamycin resistance and the report of results to the physician for prescribing of these two antibiotics for treatment of infections caused by inducible clindamycin resistance strains and replace with the appropriate treatment regimen is very important.