Clinical availability of neonatal blood culture results at 48 hours

Background/aim: To minimize the use of antibiotics in the neonatal unit, it is crucial to know the time needed for a blood culture to become positive. With the development of newer automated blood culture systems, the time needed to detect a positive culture is said to be reduced to 48 hours. The aim of this study was to determine the time at which neonatal blood culture results become clinically available to the attending neonatologist. Design and methods: In an eighteen-months-period prospective study we collected 361 blood cultures from neonates admitted to our neonatal unit. Time to positivity (TTP) (the time between culture sampling and the moment the neonatologist received the results) was determined. Incubation time (time actually spent in the Bactec machine) was automatically registered. Results: 72 out of 361 blood cultures were positive (20%). 93% (67/72) of the positive cultures had a TTP of less than 48 hours. One sample had a TTP of 50 and one of 53 hours. Three samples had an incubation time of more than 94 hours. A total of 99% (68/69) of the remaining cultures were positive within 30 hours of incubation. Conclusion: This study demonstrated that 93% of blood cultures results are determined by 48 hours. Incubation time in the Bactec is consistent with reliable detection of pathogen microbes by 30 hours. If effort is made to improve logistics TTP can further be reduced to 30 hours resulting in further reduction of antibiotic usage in neonatal intensive care units.