Coagulase negative Staphylococci from blood cultures: contaminants or pathogens?

Detailed clinical data, underlying conditions, inflammatory indices and microbiological parameters in 60 patients who had pure growth of coagulase negative staphylococci from their blood culture specimens at the University Hospital of the West Indies, Jamaica, were analyzed and the clinical significance of the isolates ascertained using standard criteria. This study was undertaken between April and September 2003. The isolates were true pathogens of bloodstream infections in only 5 of the 60 patients (8.4%). In the vast majority ie 44 of 60 (73.3%) they were mere blood culture contaminants and in 11 (18.3%), the clinical significance could not be ascertained Fifteen of the 44 patients (34%) with contaminating coagulase negative staphylococci were treated with specific anti-staphylococcal antibiotics; 5 (11.4%) with vancomycin. Although there has been a relative increase of coagulase negative staphylococcal infections including bloodstream infections in recent years, the organisms still remain the most common contaminants in blood cultures. Over 70% of isolates were contaminants in this study which is similar to that in a number of such studies in other parts of the world The findings underline the need for careful evaluation of coagulase negative staphylococci isolated from blood cultures before instituting therapy to avoid unnecessary use of antibiotics, especially vancomycin, and the consequent increase of antibiotic resistance in hospitals.