Species distribution of coagulase negative staphylococci isolated from different clinical specimens.

Staphylococci are Gram positive, non motile, asporogenous bacteria that characteristically divide in more than one plane to form irregular cluster. Species are classified as coagulase-positive Staphylococcus aureus and coagulase-negative staphylococci. Coagulase-negative staphylococci (CoNS) are reported to be the third causative agent of nosocomial infections and the most frequent cause of nosocomial bloodstream infections. Strains of CoNS those are resistant to methicillin referred to as Methicillin Resistant Coagulase Negative Staphylococci (MRCoNS). Now a days, MRCoNS has been increasing as a serious nosocomial pathogen having the property of multi drug resistance. The present study was conducted to see the species distribution, antibiotic resistance patterns and some virulence factors of CoNS isolated from different clinical specimens. This cross sectional descriptive study was carried out in the Department of Microbiology, Mymensingh Medical College during the period from July 2009 to May 2011. A total of 300 clinical specimens were collected for this study of which 240 were found culture positive as single isolate. Among them 110 were from surgical wound, 80 from pus of skin infections, 30 from burn ulcer exudates and 20 from diabetic ulcer exudates. A total of 80 strains of CoNS were isolated from them. Besides CoNS other isolated bacteria were S. aureus, Pseudomonas spp and Escherichia coli. The CoNS were initially detected by coagulase test. All the strains that were either slide or tube coagulase negative were further identified by different biochemical tests using a commercial kit HiStaph™ Identification Kit (HiMedia Laboratories Ltd) which comprise a set of 12 standard biochemical tests. A total of 16 species were identified. These were S. epidermidis, S. saprophyticus, S. caprae, S. haemolyticus, S. simulans, S. xylosus, S. hyicus, S. hominis, S. warneri, S. auricularis, S. lugdunensis, S. felis, S. capitis, S. chromogenes, S. carnosus and S. gallinarum. Of them S. epidermidis was the most prevalent (17%) followed by S. saprophyticus (15%), S. caprae (11%), S. haemolyticus (9%).