Inducible clindamycin resistance in Staphylococcus aureus isolated from clinical samples

Clindamycin is commonly used in the treatment of erythromycin resistant Staphylococcus aureus causing skin and soft tissue infections. In vitro routine tests for clindamycin susceptibility may fail to detect inducible clindamycin resistance due to erm genes resulting in treatment failure, thus necessitating the need to detect such resistance by a simple D test on routine basis.

247 Staphylococcus aureus isolates were subjected to routine antibiotic susceptibility testing including oxacillin (1ìg) by Kirby Bauer disc diffusion method. Inducible clindamycin resistance was detected by D test, as per CLSI guidelines on erythromycin resistant isolates.

36 (14.5%) isolates showed inducible clindamycin resistance, nine (3.6%) showed constitutive resistance while remaining 35 (14.1%) showed MS phenotype. Inducible resistance and MS phenotype were found to be higher in MRSA as compared to MSSA (27.6%, 24.3% and 1.6%, 4% respectively).

Study showed that D test should be used as a mandatory method in routine disc diffusion testing to detect inducible clindamycin resistance.