To determine the incidence, microbiology, risk factors, and outcomes related to bloodstream infections (BSIs) concurrent with the onset of necrotizing enterocolitis (NEC).

We performed a retrospective review of all cases of NEC in a single center over 20 years. BSI was categorized as “NEC-associated” if it occurred within 72 hours of the diagnosis of NEC and “post-NEC” if it occurred >72 hours afterwards. Demographics, hospital course data, microbiologic data, and outcomes were compared via univariate and multivariate analyses.

NEC occurred in 410 infants with mean gestational age and birth weight of 29 weeks and 1290 g, respectively; 158 infants were diagnosed with at least one BSI; 69 (43.7%) with NEC-associated BSI, and 89 (56.3%) with post-NEC BSI. Two-thirds of NEC-associated BSI were due to gram-negative bacilli compared with 31.9% of post-NEC BSI (OR: 4.27; 95% CI: 2.02, 9.03) and 28.5% of all BSI in infants without NEC (OR: 5.02; 95% CI: 2.82, 8.96). Infants with NEC-associated BSI had higher odds of requiring surgical intervention (aOR: 3.51; 95% CI: 1.98, 6.24) and death (aOR: 2.88; 95% CI: 1.39, 5.97) compared with those without BSI.

BSI is a common, underappreciated complication of NEC occurring concurrent with the onset of disease and afterwards. The microbiologic etiology of NEC-associated BSI is different from post-NEC and late-onset BSI in infants without NEC with a predominance of gram-negative bacilli. Infants with NEC-associated BSI are significantly more likely to die than those with post-NEC BSI and NEC without BSI.