What is the role of infectious organisms in the etiology of 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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Although infectious organisms have long been thought to play a key role in the development of NEC, specifics regarding this role continue to be elusive. Whether bacterial infection has a primary inciting role in NEC or whether an initial intestinal mucosal injury allows secondary bacterial invasion is unclear. Is it a straight-forward "infection" with a pathogenic organism that starts the disease cascade, or is it more complex? Positive blood cultures are found in 30% of patients; the most commonly identified organisms are Escherichia coli and Klebsiella pneumoniae. Proteus mirabilis, Staphylococcus aureus, S epidermidis, Enterococcus species, Clostridium perfringens, and Pseudomonas aeruginosa have also been identified.

However, more recent research is focusing not on individual species but rather the role of the premature gut microbiome as a risk factor. Unlike term infants, the premature gut becomes colonized with a limited number of bacterial species, the majority of which are gram-negative organisms in the Gammaproteobacteria class. [3, 4]  Termed "inappropriate colonization," or "dysbiosis," this class of bacteria has been shown in animal models to produce short-chain fatty acids and other bioactive substances, affecting epithelial cell health and integrity. How these mediators impact the immature gut continues to be explored. [5] This line of inquiry has been further supported by observational studies that have shown breastfed infants (not breast-milk fed) and those advanced more quickly to full enteral feeds were less likely to develop NEC than their counterparts. [5, 6]

E coli, Klebsiella species, Enterobacter cloacae, P aeruginosa, Salmonella species, S epidermidis, C perfringens, C difficile, and C butyricum commonly grow in stool cultures. Klebsiella species, E coli, S epidermidis, and yeast are most commonly identified on peritoneal cultures. Fungal infection is believed to be an opportunistic infection in the presence of an altered host intestinal defense system.

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