Yield of aerobic, anaerobic, and fungal blood cultures from neonates admitted to the Children\u27s National NICU

Blood cultures are the most sensitive method of detecting a bloodstream infection; however, obtaining adequate volume of blood in a neonate can be difficult. In the NICU at our institution, standard practice is to obtain aerobic and anaerobic blood cultures from neonates with suspected sepsis, and the practice of drawing a fungal blood culture is physician-dependent. The aim of this study is to assess the yield of pathogen isolation from aerobic, anaerobic, and fungal blood cultures in order to inform effective management in neonates while minimizing unnecessary testing. We completed retrospective review of charts of NICU patients from whom aerobic, anaerobic, and/or fungal blood cultures were drawn between 1/1/2015 and 12/31/2016. The yield of positive culture was calculated, and the organisms isolated from these cultures were reviewed. The medical records of those patients that grew organisms in only one bottle were reviewed to determine if the organism was a likely contaminant, using the CDC/NHSN definition of bloodstream infections. Over the two years, 1,518 aerobic blood cultures were drawn, of which 71 were positive (4.7%), 934 anaerobic blood cultures were drawn, of which 33 (3.5%) were positive, and 496 fungal blood cultures were drawn, of which 1 (0.2%) was positive. Of 48 instances in which there was a positive culture from at least one blood culture bottle at a time when both an anaerobic and an aerobic blood culture was obtained from the same patient at the same time, 26 yielded an organism in both bottles (54% of positive cultures), 15 yielded an organism in the aerobic bottle alone (31% of positive cultures), and 7 yielded the organism in the anaerobic bottle alone (15% of positive cultures). Of the 7 cases in which an organism grew from the anaerobic bottle but not the aerobic bottle, 4 (2 S. epidermidis, 1 Corynebacterium sp., 1 S. simulans) were considered contaminants by the primary team and not treated, 2 (S. capitis, Streptococcus sp.,) were treated but would have been considered contaminants by CDC/NHSN definition, and 1 (S. aureus) was treated as a true infection. The single positive fungal culture grew Candida albicans at 89 hours to positivity. The majority of true bacterial and fungal pathogens which grew by blood culture could be isolated from aerobic culture bottles. The low yield of anaerobic and fungal blood cultures in this study calls into question the utility of their routine use in neonates