Species distribution of coagulase-negative staphylococcal isolates at a community hospital and implications for selection of staphylococcal identification procedures.

A total of 499 coagulase-negative staphylococci (CoNS) were isolated from a variety of clinical specimens at a community hospital. Ten different species and many strains of CoNS were identified. Staphylococcus epidermidis was the most common isolate. The species distribution suggests that S. saprophyticus and, to a lesser extent, S. haemolyticus may be important in urinary tract infections. S. lugdunensis may be a significant isolate from wound infections. Frequently, mixed cultures were found with either multiple species or multiple strains of the same species of CoNS. These mixed cultures could not be detected by colony morphology upon initial overnight incubation of the cultures but could be distinguished following colony development for several days. In addition, sequential positive cultures from an individual patient often yielded different species or different strains of the same species which again could not be detected upon initial observations of colony morphology. Procedures for the identification of the CoNS need to be improved, and microbiology laboratories should consider the use of more definitive identification procedures for the CoNS.