Inducible clindamycin resistance in Staphylococcus aureus isolates from a tertiary care hospital, Odisha

Background: In this era of increasing antibiotic resistance, Methicillin-resistance Staphylococcus aureus (MRSA) is a very well-known superbug. Clindamycin is a commonly used drug for treatment of the MRSA strains. Due to widespread use of this drug, it has developed resistance by different mechanisms. One of the common mechanisms is inducible clindamycin resistance caused by the target site modification mediated by erm genes, which can lead to therapeutic failure even if there is invitro susceptibility to clindamycin. So, as per The Clinical and Laboratory Standard Institute (CLSI), D-test can used routinely overcome this problem. Aim: D-test is a very simple and reliable procedure demonstrated in our study aimed to detect the prevalence of inducible clindamycin resistance in our geographic area, along with establishing its relationship with isolated MRSA strains. Materials and Methods: Two hundred twenty-eight S. aureus isolates were evaluated for MRSA by using cefoxitin disc (30 μg), and inducible resistance to clindamycin was detected by D-test using Kirby–Bauer method, according to CLSI guidelines. Results: Among 228 S. aureus isolates, 53 (23.2%) showed D-test positive, that is, inducible clindamycin resistance. Among the 126 MRSA isolates 47 (37.3%) and among 102 MSSA isolates 6 (5.8%) showed inducible resistance to clindamycin. Conclusion: One study demonstrated constitutive and inducible clindamycin resistance was seen to be higher in MRSA isolates as compared to the MSSA isolates which can be detected by D-test. So, microbiology laboratories should include D-test in their routine testing protocol to avoid therapeutic failure of clindamycin.