INDUCIBLE CLINDAMYCIN RESISTANCE IN STAPHYLOCOCCUS AUREUS ISOLATES AND ITS CORRELATION WITH MULTIDRUG RESISTANCE: A STUDY FROM NORTH INDIA

CONTEXT In Staphylococcus aureus strains with inducible resistance antibiotic therapy with clindamycin may select constitutive erm gene mutants in vivo leading to clinical failure. Therefore, it is imperative to do a simple 'D-test' to detect isolates with inducible clindamycin resistance. Very few studies are available to state whether or not this inducible resistance has any correlation with multidrug resistance. AIMS To find out the prevalence of inducible clindamycin resistance amongst S. aureus isolates from various clinical specimens and determine its correlation with multidrug resistance. SETTINGS AND DESIGN A prospective study done in the Department of Microbiology in a tertiary care hospital for a period of ten months. METHODS AND MATERIAL All strains of S. aureus isolated from various clinical specimens were subjected to Antibiotic Susceptibility Testing as per CLSI guidelines and methicillin resistance was detected using cefoxitin. All the erythromycin resistant and clindamycin susceptible isolates were further subjected to 'D-Test.' STATISTICAL ANALYSIS USED Data was entered in Microsoft excel and analysed using SPSS version 16. Frequencies and proportions were done. Chi square test was the test of significance. RESULTS Out of 1153 S. aureus strains isolated 49.8% were methicillin resistant and 50.2% were methicillin susceptible. Prevalence of inducible phenotype, MS phenotype and constitutive phenotype was 18.4%, 22.1%, 18.4% respectively. Resistance to penicillin, amoxicillin-clavulanic acid, ciprofloxacin, sulphamethoxazole-trimethoprim was 92.1%, 47.8%, 43.4% and 49.3% respectively, whereas none of the isolates showed resistance to vancomycin, teicoplanin and linezolid. About 22.8%, 41.6% and 82.9% isolates with inducible phenotype, MS phenotype and constitutive phenotype respectively were multidrug resistant. CONCLUSION Prevalence of multidrug resistance is least likely with inducible clindamycin resistance than with other phenotypes.