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NJBMS - Volume 2, Issue 3, January - March 2012

Pages: 236-239
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PREVALENCE OF INDUCIBLE CLINDAMYCIN RESISTANCE IN CLINICAL ISOLATES OF STAPHYLOCOCCUS AUREUS IN A TERTIARY CARE HOSPITAL

Author: AH. shruti, J. Malini, BL. Umapathy, G. Arun Kumar

Category: Microbiology

Abstract:

Resistance to macrolides in Staphylococci may be due to active efflux encoded by msrA or ribosomal target modification [macrolide-lincosamide-streptogramin B (MLSB) resistance], encoded by ermA or ermC genes. MLSB resistance is either constitutive or inducible following exposure to a macrolide.

Aim : This study was undertaken to detect the presence of inducible clindamycin resistance among clinical isolates of Staphylococcusaureus using 'D' test .

Settings and Design : A total of 200 non duplicate Staphylococcus aureus isolates from various clinical samples from both outpatients and inpatients were studied.

Materials and Methods : Two hundred bacteriologically confirmed Staphylococcus aureus isolates were subjected to routine antibiotic susceptibility test including cefoxitin by Kirby-Bauer disc diffusion method. Inducible clindamycin resistance was detected by 'D' test as per CLSI guidelines on erythromycin resistant isolates.

Results : Among 200 Staphylococcus aureus strains,77 (38.5%) were identified as Methicillin resistant Staphylococcus aureus (MRSA) and 123 ( 61.5%) as Methicillin sensitive Staphylococcus aureus (MSSA). Twenty five (12.5%) isolates showed inducible clindamycin resistance (iMLSB), 11 (5.5%) showed constitutive resistance (cMLSB) while remaining 19 (9.5%) were erythromycin resistant and clindamycin sensitive strain (MSB) phenotype. Remaining 145 (72.5%) strains were sensitive to both clindamycin and erythromycin . Inducible and constitutive phenotypes were found to be higher in MRSA ( 28.6% & 13%) as compared to MSSA ( 2.4% & 0.8% ).

Conclusion : Study showed that 'D' test should be included in the routine antibiotic susceptibility testing as it will guide the clinician about the iMLSB phenotype of Staphylococcus aureus, so that clindamycin may be used judiciously.

Keywords: : Staphylococcus aureus, MRSA, MSSA, iMLSB, cMLSB, MSB phenotypePrevalence of inducible clindamycin resistance in clinical isolates of Staphylococcus aureushospital in a tertiary care hospital