Paucity of Bacteria Implicated in Pathogenesis of Experimental Necrotizing Enterocolitis
Joanna Lim, Children's Hospital Los Angeles; Gene Jang, Children's Hospital Los Angeles; Brandon Bell, Children's Hospital Los Angeles; Jamie Golden, Children's Hospital Los Angeles; Jordan Bowling, Children's Hospital Los Angeles; Jin Wang, Children's Hospital Los Angeles; Larry Wang, Children's Hospital Los Angeles; Anatoly Grishin, Children's Hospital Los Angeles; Henri Ford, Children's Hospital of LA, University of SC
Although the etiology of necrotizing enterocolitis (NEC) is not clear, abnormal bacterial colonization of the gastrointestinal tract may play a critical role in its pathogenesis. Consistent with this theory, prompt administration of broad spectrum antibiotics remains a cornerstone of clinical management of NEC. However, administration of antibiotics to vulnerable infants could predispose to the development of NEC by altering the intestinal microbial flora.Hypothesis:
We hypothesize that antibiotic administration predisposes to the development of NEC by altering the intestinal microbiota.Methods:
We induced NEC in neonatal rats by subjecting them to formula feeding and hypoxia thrice daily. There were six treatment groups: formula feeding/hypoxia alone; or with early (starting day of life #1); or late (starting day of life #3) ampicillin administration; addition of the opportunistic pathogen Cronobacter muytjensii alone; or in combination with early or late ampicillin administration. Animals were sacrificed on day of life #4. The terminal ileum was scored histologically (NEC ≥2). Microbiota was characterized by culture-based 16S rRNA sequencing.Results:
Formula feeding and hypoxia alone caused an NEC incidence of 29%. As expected, C.muytjensii increased the incidence of NEC to 69% (p=0.0013 compared to baseline). However, the total bacterial load in this group was low, 102-105/mL specimen. When ampicillin was given early with C. muytjensii, the incidence of NEC decreased to 25% (p=0.0185 compared to C.muytjensii alone) but the total bacterial load was higher, ranging 107-109/mL. Late administration of ampicillin with C.muytjensii resulted in an incidence of 71% (p=0.0047 compared to baseline) and a low total bacterial load of less than 102/mL. Ampicillin alone, regardless of timing, produced a high incidence of NEC (early 67%, late 75%) and low bacterial load of less than 102/mL.Conclusions:
C. muytjensii not only exacerbates NEC but decreases colonization of other bacterial species, possibly by competition. Ampicillin is beneficial when administered early together with a susceptible opportunistic pathogen. This beneficial effect is associated with increased colonization by other bacteria. Thus, early targeted antibiotic administration against an opportunistic pathogen may limit its growth while allowing subsequent colonization of commensal bacteria. However, antibiotic administration in the absence of a putative pathogen could be detrimental and lead to the development of NEC.