Ramanand Kumar Pappu, Chandan Kumar Poddar, Suman Kumar, Ram Nagina Sinha4, S. K. Shahi
BACKGROUND Staphylococcus aureus is one of the most common pyogenic bacteriae infecting man, causing both hospital and community acquired infections. Staphylococcus aureus can produce a wide variety of diseases, from relatively benign skin infections. The Clinical and Laboratory Standards Institute (CLSI) recommends D-test, which is a phenotypic screening method for inducible clindamycin resistance. Therefore, all erythromycin resistant S. aureus should be tested for inducible clindamycin resistance to prevent clindamycin treatment failures and to report prevalence of resistant phenotypes which varies widely. MATERIALS AND METHODS This cross-sectional study was conducted for a period of one year from January 2016 to January 2017. We analysed 110 nonduplicate consecutive isolates of S. aureus isolated from various clinical specimens like pus, wound swab, aspirates, blood, and sterile fluids. A total of 110 S. aureus isolates derived from wound infection were evaluated for antimicrobial susceptibility testing by Kirby Bauer disk diffusion method. Methicillin resistance was detected using cefoxitin (30 μg) disk and inducible clindamycin resistance was determined in all erythromycin resistant isolates by using D-zone test. RESULTS Out of 110 S. aureus isolates of the MRSA 38 (34.6%) were derived from respectively pus samples 16 (41.53%), the S. aureus isolates derived from wound samples were MRSA 7 (18.03%), the S. aureus isolates derived from blood samples were MRSA 9 (22.40%), the S. aureus isolates derived from miscellaneous samples were MRSA 5 (13.66%) and the S. aureus isolates derived from urine samples were MRSA 1 (3.75%). A total of 26 S. aureus isolates showed inducible clindamycin resistance by giving a positive D-zone test, hence, its prevalence was found to be 21.10% (23/110), with percentage distribution of cMLSB phenotype and MS phenotypes in all S. aureus isolates as 19.6% and 24.4% respectively. The antimicrobial susceptibility test result of all the 24 S. aureus isolates with iMLSB phenotype revealed that they were 100% sensitive to vancomycin and linezolid, with moderate sensitivity (71.14%) to gentamicin, cefuroxime and least sensitivity to (23.81%) doxycycline, (20.95%) ciprofloxacin. CONCLUSION Due to high prevalence of erythromycin resistance amongst S. aureus isolates, we suggest that D-zone test should be routinely done in all laboratories for appropriate prescription of clindamycin and thereby preventing emergence of inducible resistant strains and treatment failure.
