In Vitro Study of Constitutive and Inducible Clindamycin Resistance in Staphylococcus Aureus with Reference to Methicillin Resistant Staphylococcus Aureus: Experience From Tertiary Care Hospital in Punjab

Backround: Serious infections due to methicillin resistant Staphylococcus aureus (MRSA) have become a major clinical challenge. Globally Macrolide-lincosamide streptogramin B family of antibiotics are commonly used to treat such infections as an alternative to vancomycin. The study was to conducted to find out the presence of inducible clindamycin resistance among Staphylococcus aureus and their association with methicillin resistance.

Method: The study conducted over one year (Jan 2016 - Dec 2016) in microbiology department of Guru Gobind Singh Medical College, Faridkot. Two hundred fifteen S.aureus isolates were included in the study. Methicillin resistance was detected by cefoxitin (30μg) disc diffusion method and inducible clindamycin resistance by erythromycin and clindamycin disc approximation test (D-Test).

Results: Of the 215 clinical isolates of S. aureus, 140 (65.11%) were MRSA. Erythromycin and clindamycin resistance was seen in 79.06%(170/215) and 49.30% ( 106/215) respectively. Resistance to erythromycin and clindamycin were higher in MRSA than MSSA (erythromycin resistance:100%v s 22.5% and Clindamycin resistance:70.1% vs 10.6%). Both iMLSB and cMLSBphenotypes are predominant in MRSA.

Conclusion: Detection of MRSA in our study shows the need to improve health care practices and to formulate new infection control policies to control MRSA infections. Inducible and constitutive resistance is comparatively higher in our study in MRSA .So It is necessary to perform D-test for detection of inducible clindamycin resistance among MRSA in routine antibiotic sensitivity testing so that therapeutic failures can be avoided.