Phenotypic detection of inducible clindamycin resistance by D-test in Staphylococci from various clinical samples

Abstract

Background: Staphylococcus aureus is a major opportunistic human pathogen causing many clinical infections. Three MLSB phenotypes are known in S. aureus, a constitutive resistant phenotype (cMLSB), a clindamycin-susceptible phenotype in vitro with inducible resistance in vivo (iMLSB), and a clindamycin-susceptible and macrolide-steptogramin B-resistant phenotype (MSB). Method: This prospective-observational study was carried out in Department of Microbiology, NIMS medical college, Jaipur, Rajasthan from July 2023 to Sept 2024. A total of 50 Staphylococci were isolated from different types of samples. All the Staphylococcus aureus isolates that were resistant to erythromycin were tested for inducible Clindamycin resistance by double disk approximation test (D-test) as per CLSI guidelines. Result: A total of 50 Staphylococci isolates, MSSA were 18 (36%) followed by CONS 12 (24%), MR-CONS 12 (24%) and MRSA 8 (16%). Out of total 50 isolates, 17 (34%) showed inducible resistant by D-test. In which MSSA were 3 (18%), CONS 5 (29%), MR-CONS 4 (24%) and MRSA 5 (29%). Inducible resistance was observed among various clinical samples like, Blood samples 10 (60%) followed by Pus 5 (30%), Wound Swab 1(5%), and High Vaginal Swab 1(5%). Discussion: In this study we found 34% inducible clindamycin resistance by D-test. Similar, findings observed in various studies also. Conclusion: Highest percentage of inducible resistance found in isolates from Blood sample. Clinical microbiology laboratories should report inducible Clindamycin resistance in Staphylococcus aureus and D-test can be used as a simple, auxiliary and reliable method to Delineate inducible and constitutive Clindamycin resistance in routine clinical laboratories.