DETECTION & CORRELATION OF INDUCIBLE AND CONSTITUTIVE CLINDAMYCIN RESISTANCE WITH METHICILLIN RESISTANCE IN COAGULASE NEGATIVE STAPHYLOCOCCI

Dr. Vidit Goyal, Dr. S Makhija

Abstract


Background: CoNS are one of those amongst the commonly isolated organisms in the clinical microbiology laboratory. Interest in CoNS is increasing because of their role as pathogens in hospital-acquired infections (HAI) associated with catheters and implanted medical devices and their marked resistance to antibiotics.

CoNS strains are commonly multi-resistant to various groups of antibiotics.The macrolide-lincosamide-streptogramin B (MLSB) family of antibiotics is commonly used in the treatment of staphylococcal infections.(35) However, one important issue in clindamycin treatment is the risk of clinical failure during therapy.

Materials and Methods: 

METHICILLIN RESISTANCE : In this study methicillin resistance was tested by cefoxitin disk (30µg) diffusion method as per CLSI guidelines, INDUCIBLE CLINDAMYCIN RESISTANCE: All CoNS isolates were tested for the inducible clindamycin resistance by Double-disk diffusion test (D-zone test) as per CLSI guidelines.

Results: 234 Coagulase Negative Staphylococcial strains from different clinical specimen were processed. Methicillin resistance was shown by 65.38% isolates. Inducible clindamycin resistance was found to be 31.3% & 14.28% respectively in MRCoNS & MSCoNS Similerly constitutive clindamycin resistance was found to behigher in MRCoNS at 57.39% & then in MSCoNS (35.71%).

 

Conclusion: Clindamycin disk induction test (D-zone test) is simple and must be done routinely in the diagnostic microbiology laboratories. Without the “D-zone test” all the CoNS isolates with inducible clindamycin resistance would be erroneously classified as clindamycin susceptible by routine testing methods. Constitutive & inducible clindamycin resistance was found to be more prevalent in MRCoNS then MSCoNS.


Keywords


Coagulase Negative Staphylococci, Methicillin Resistance, Inducible clindamycin resistance, Constitutive clindamycin resistance, D test

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