Speciation of coagulase negative Staphylococcal isolates from clinically significant specimens and their antibiogram

Despite their frequency as contaminants, coagulase-negative Staphylococci (CONS) have become important nosocomial pathogens, accounting for 9% of all nosocomial infections. These infections are difficult to treat because of the risk factors and the multiple drug resistance nature of these organisms.

One hundred and two consecutive CONS were isolated from various clinical samples like blood, pus, urine, urine catheter tip and gastric lavage. Most of the blood samples were from patients with risk factors (immunocompromised or on medical devices). After confirming the isolates as CONS, species-level identification was performed by simple, non-expensive conventional methods and antibiotic sensitivity testing was also carried out.

Of 102 CONS isolates, 100 isolates could be identified to the species level. Among the 100 isolates, epidermidis was the most common species isolated, seen in 32%, followed by S. hemolyticus (18%), S. lugdunensis (12%), S. hominis (10%), S. saprophyticus (8%), S. capitis (6%), S. caprae (4%), S. xylosus (4%), S. cohni and S. warneri (3% each). In the present study, 56% of the isolates were methicillin-resistant CONS. Most of the isolates showed resistance to ampicillin and amoxyclav (89% each), followed by ceftriaxone (52%), cotrimoxazole (46%), cefotaxime (32%), gentamicin (25%), amikacin (21%).

The increased pathogenic potential and multiple-drug resistance demonstrates the need to adopt simple, reliable and non-expensive methods for identifying and determining the antibiotic sensitivity of CONS.