Optimum Time to Detection of Bacteria and Yeast Species with BACTEC 9120 Culture System from Blood and Sterile Body Fluids

The culture results of 4,807 blood and 383 sterile body fluid specimens received in our laboratory during a 54-month period, were analyzed to determine the time required for culture to become positive, time at which a culture could safely be considered negative, and the spectrum of isolated organisms. The specimens were processed by automated BACTEC 9120 culture system. A total of 1,677 clinically significant microorganisms were isolated. Gram positive and negative bacterial isolation rates were found to be 62.55% and 32.20%, respectively. Yeasts were recovered in 5.24%. False positivity rate was 1.5%. Clinically significant isolates recovered on day four and five were 97.81% and 99.88%, respectively. At day five, the sensitivity was 99.94% and negative predictive value 99.96%. Our data support a five-day incubation protocol for recovery of all clinically significant organisms with sensitivity reduced by 0.06%, when compared with a six-day protocol.