STUDY OF SPECIES IDENTIFICATION AND ANTIMICROBIAL SUSCEPTIBILITY OF VARIOUS CLINICAL ISOLATES OF COAGULASE – NEGATIVE STAPHYLOCOCCI

Abstract

BACKGROUND- Interest in CoNS is increasing because of their role as pathogens in certain clinical conditions and their marked resistance to antibiotics. Frequent isolation of CoNS from the blood, other normally sterile body fluids, intravenous catheters and various tissues presents a recurrent interpretative challenge to both the clinician and microbiologist. The ubiquity of these organisms does present problems when one is faced with making a decision as to whether their isolation in clinical laboratory represents true infection or merely contaminant .AIM-The aim of this study was to isolate, identify and speciate coagulase negative staphylocci (CoNS) from clinical specimens, along with to find their resistance to antimicrobial agents with reference to their methicillin resistance .MATERIAL & METHOD - Various clinical specimens like blood, pus, wound swab, ascitic / synovial fluid, urine, cerebro spinal fluid were processed in laboratory following the standard protocol for isolation, identification and speciation of coagulase negative staphylococci. RESULT- Present study found, S. epidermidis to be most prevalent species of coagulase negative staphylocci from clinical isolates with 47.58% strains, followed by S. haemolyticus 26.06%, and S. lugdunensis 8.54%. S. saprophyticus was the most common of CoNS species from urinary tract infection cases. Methicillin resistant CoNS (MRCoNS) were detected by cefoxitin disk diffusion method Out of 234 strains of CoNS, 153 strains (65.38%) were detected as MRCoNS. Most of the MRCoNS were found to be resistant to penicillin (100%), ceftazidime (99.35%), amoxicillin-clavulanic acid (98.69%), cotrimoxazole (92.81%), gentamicin (88.23%).Susceptibility to vancomycin and pristinamycin was 86.93 % and 99.35% respectively while all the MRCoNS isolates were susceptible to linezolid. CONCLUSION - Vancomycin is the mainstay of therapy in MDR MRCoNS infections and should be used judiciously. Looking at the possibility of emergence of resistance to the drug, newer agents like linezolid and pristinamycin might provide a valuable option for the treatment of MRCoNS infections. There is a need to have the knowledge and monitoring of antibiotic sensitivity pattern and formulation of definite antibiotic policy to improve the empirical approaches to the therapy of serious infections caused by CoNS