What is the evidence in support of an infectious etiology in necrotizing enterocolitis (NEC)?

Updated: Dec 27, 2017
  • Author: Shelley C Springer, JD, MD, MSc, MBA, FAAP; Chief Editor: Muhammad Aslam, MD  more...
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Answer

New opportunistic and pathologic bacteria are being identified and speciated, especially as the protective role of probiotics continues to be elucidated. [4] Infant formulas contaminated with organisms such as Cronobacter species (previously called Enterobacter sakazakii) [7] further complicate the picture as to whether the formula or the bacteria are implicated in the disease or, conversely, whether the breast milk or the bacteria are protective.

The observation of an epidemic or cluster of cases in a short period in one nursery after sporadic cases supports the key role of infectious organisms in NEC. Nursery personnel are known to experience acute gastrointestinal (GI) illnesses in association with these outbreaks, and the institution of infection control measures has accordingly reduced the rates of NEC.

Rat pups colonized with Staphylococcus aureus and Escherichia coli demonstrated increased incidence and severity of necrotizing enterocolitis compared with those whose intestines were populated with various bacterial species. [8] Toll-like receptor signaling of intestinal mucosal transmembrane proteins is accomplished by binding of specific bacterial ligands that mediate the inflammatory response; the character of the intestinal bacterial milieu is thought to play a role in the up-regulation or down-regulation of intestinal inflammation via toll-receptor signaling.

Many preterm infants receive frequent exposure to broad-spectrum antibacterial agents, further altering the intra-intestinal bacterial environment. Advances in genome sequencing of the gut microbiome of healthy as well as affected premature infants, along with the roles of host molecular and immune factors, continue to raise more questions than answers about the multifactorial etiology of this devastating condition. [3, 5]

That NEC is related to gut colonization of pathogenic flora is supported by findings showing administration of physiologic flora decreases the incidence of NEC. The protective effect of breast milk is thought, in part, to be related to delivery of Lactobacillus species that somehow repair the intestinal milieu. Work by Blackwood, et al suggests that the mechanism is more elegant: Both in vitro and in vivo models showed improved intestinal integrity in rat pups fed L rhamnosus and L plantarum probiotics. [9] By increasing capillary tight junctions, tested animals experienced less intestinal injury compared to control animals when challenged with a known cellular toxin. [9]


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