Incubation time required for neonatal blood cultures to become positive

Incubation time required for neonatal blood cultures to become positive

Jardine L; Davies MW; Faoagali J

Journal Of Paediatrics And Child Health

2006

Humans; infant; Time Factors; Birth Weight; Newborn; retrospective studies; Bacteremia/blood/diagnosis/microbiology; Bacteriological Techniques/methods; Blood/microbiology; Sepsis/blood/diagnosis/microbiology

AIM: We aimed to determine the laboratory detection time of bacteraemia in neonatal blood cultures, and whether this differed by: organism; samples deemed to represent true bacteraemia versus contaminants; and blood cultures collected from an infant or=48 h of age (late). METHODS: A retrospective audit of all positive blood cultures collected from neonates in the Grantley Stable Neonatal Unit, Royal Women's Hospital, Brisbane, between 1 January 2000 and 31 December 2004 was undertaken. The bacteraemia detection method used was the BacTAlert system with Peds bottles. RESULTS: Two hundred and three positive blood cultures were included in the analysis. One hundred and sixteen (57%) were deemed septicaemia, 87 (43%) were deemed contaminants. The median (interquartile range) time to positivity for positive blood cultures deemed septicaemia and contaminants were 15.9 (11.6, 22.2) and 30.2 (20.4, 43.9) h, respectively. Fifty-six (28%) positive blood cultures were collected when infants were or=48 h of age. Post hoc analysis revealed that the time to positivity for early septicaemia was 13.7 (11, 16.7) h; early contaminant was 25.2 (19.2, 33.8) h; late septicaemia was 17.2 (12.2, 23.4) h; and late contaminant was 37.9 (21.7, 51.2) h. The time to positivity for: Group B streptococcus was 9.3 (8.2, 11.0) h; Escherichia coli was 11.3 (10.0, 13.5) h; and coagulase-negative staphylococci was 28.9 (20.5, 41.2) h. CONCLUSION: The incubation time for positive blood cultures significantly differs by organism type and whether they are considered early or late septicaemia versus contaminants. We recommend that: infants who are or=48 h of age at the time of collection should continue antibiotic treatment for at least 48 h before cessation is considered.

2006

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