Objective: Early diagnosis and treatment of bloodstream infections, which are one of the major causes of morbidity and mortality, are clinically important. Blood culture is still the gold standard for detection of microorganisms in the blood. The purpose of this study was to review the results of blood cultures which were evaluated at Microbiology Laboratory, of Yeditepe University Hospital, Istanbul, Turkey between 2006 and 2008.

Materials and Methods: Blood specimens obtained from patients with suspected bloodstream infections had been cultured in BACTEC 9120 automated blood culture system. Specimens without growth were reported negative following seven days of incubation. The specimens which yielded a growth signal, were subcultured to 5% sheep blood agar, chocolate agar, Gram stained and were identified by standard microbiological methods and a mini-API system.

Results: A total of 5663 blood cultures obtained from hospitalized patients between 2006-2008 were evaluated. Number of positive blood cultures were 273/1434 (19.04%), 408/2229 (18.30%) and 224/ 2000 (11.20%9) in 2006, 2007 and 2008, respectively. The number of false positivity was 5 (0.35 %) in 2006; 34(1.52 %) in 2007 and 4 (0.20%) in 2008. Coagulase negative staphylococci were the most commonly isolated microorganisms from blood cultures in each of the three study years.

Conclusion: Factors affecting the yield of blood cultures should be searched and evaluated regularly in every center. The rate of false positive blood cultures was within the acceptable limit. However, quality control studies and continuous surveillance should be established to keep false positivity rates for blood cultures at the lowest limit.