Time to positivity of neonatal blood cultures : fast and furious?Time to positivity of neonatal blood cultures : fast and furious?
Faculty of Medicine and Health Sciences
Vaccine & Infectious Disease Institute (VAXINFECTIO)
Laboratory Experimental Medicine and Pediatrics (LEMP)
Journal of medical microbiology. - Edinburgh, 1968, currens
60(2011):4, p. 446-453
University of Antwerp
The aim of this study was to determine the time to positivity (TTP) of neonatal blood cultures, to investigate differences between early onset versus late-onset sepsis, and non-proven versus proven sepsis, and to examine differences in TTP by organism type using a retrospective observational study at the Neonatal Intensive Care Unit, Antwerp University Hospital, Belgium. The subjects were 1828 neonates with suspected sepsis who were treated with antimicrobials for at least 3 days. The TTP was recorded for all episodes of suspected sepsis in an approximately 6.5 year period. A total of 2916 blood cultures were collected, of which 437 (15 %) became positive. The overall TTP was 21.33 h (Q1Q3 13.1732.46). The difference between the median TTP in early onset versus late-onset sepsis was 0.83 h (22.00 versus 21.17 h, P=0.75). The median TTP for Gram-negative organisms was 11.17 h (Q1Q3 8.8415.67), whereas the median TTP for Gram-positive organisms was 23.59 h (Q1Q3 15.2934.58, P<0.001). In Gram-positive isolates, the median TTP for coagulase-negative staphylococci (CNS) was 26.67 h (Q1Q3 19.0038.17), whereas the median TTP for non-CNS was 12.83 h (Q1Q3 10.5018.17, P<0.001). The median TTP in proven sepsis was 20.17 h (Q1Q3 13.0030.37), whereas it was 29.67 h (Q1Q3 21.1750.63, P<0.001) in non-proven sepsis. TTP of neonatal blood cultures was significantly shorter for Gram-negative organisms. We suggest shortening the total incubation time of neonatal blood cultures to a maximum of 3 days. However, blood cultures collected in infants <72 h of age might require a longer incubation time. According to our results, it may be safe to narrow the antimicrobial spectrum to solely target Gram-positive bacteria when the culture is still negative after 48 h, and to cease antimicrobial therapy when the culture is still negative after 72 h in clinically well infants.