Phenotypic Detection of Inducible Clindamycin Resistance in Clinical Isolates of Coagulase Negative Staphylococci- Study from Tertiary Care Centre

Dr. Aparna Aparajita; Dr. Ashok Kumar Sharma; Dr. Manoj Kumar

Volume : IX, Issue : VIII, August - 2020

Phenotypic Detection of Inducible Clindamycin Resistance in Clinical Isolates of Coagulase Negative Staphylococci- Study from Tertiary Care Centre

Dr. Aparna Aparajita, Dr. Ashok Kumar Sharma, Dr. Manoj Kumar

Abstract :

Background : Coagulase negative staphylococci(CoNS) are colonisers of skin and mucous memane, when isolated from clinical samples were considered as contaminants but recently have gained importance as agents of nosocomial infections. The study was done to detect phenotypic expression of inducible clindamycin resistance in clinically significant isolates of coagulase negative staphylococci. Materials and methods: The study was a cross sectional study done in the Department of Microbiology RIMS, Ranchi, for a period of 1 year from July2017 to June2018. A total of 111 clinically significant isolates of Coagulase negative staphylococci were identified from various clinical samples by using standard microbiological methods. Antibiotic susceptibility testing was performed by Kirby-Bauer disc diffusion method and results interpreted using the CLSI guidelines. Methicillin resistance was detected by using cefoxitin discs (30 μg). The isolates showing clindamycin sensitive and erythromycin resistant were selected for D –test to test for inducible clindamycin resistance.The strains showing flattening of or blunting of zone of inhibition(D shaped) around CL were designated as D-test positive. Results:Methicillin resistant coagulase negative Staphylococi (MRCoNS) accounted for 39(35.2%). Three types of phenotypes were found, constitutive resistance(cMLSB), inducible resistance(iMLSB) and MS phenotype or D -test negative. The three types were determined in Methicillin sensitive and Methicillin resistant coagulase negative staphylococci(MSCoNS, MRCoNS).D-test was found to be positive in 32.1% of MRCoNS and 11.3% of MSCoNS. Constitutive resistance (cMLSB) phenotype was found in 10.2% of MRCoNS, iMLSB(inducible resistance) phenotype was found in 32.1% of MRCoNS, MS phenotype was found in 67.8% of MRCoNS. Constitutive resistance(cMLSB) phenotype was found in 13.8% of MSCoNS, iMLSB(inducible resistance) phenotype was found in 11.3% of MSCoNS, MS phenotype was found in 88.6% of MSCoNS. MS phenotype or D test negative was found in 67.8% of MRCoNS and 88.6% of MSCoNS. Conclusion: D-test is a simple and easy method for determining phenotypic expression of inducible clindamycin resistance, therefore it may be helpful to guide empirical therapy in patients with skin and soft tissue infection and avoid clinical therapeutic failures.