A complex infection pg. 2
A single layer of epithelial cells line the intestine and separate us from the outside world where bacteria live and outnumber us 10 to 1.
At birth, a newborn’s intestine is relatively sterile. Once a baby starts taking milk – either formula or breast milk -- bacteria proliferate and become the large “microbiome” inside our intestines.
For unknown reasons, something causes mild mucosal damage at the surface of these epithelial cells. When that happens, the normal bacteria that reside in the intestines adhere to the epithelium, causing inflammation and damage to the bowel.
Tumor necrosis factor (TNF) is one of the key players in NEC. In the 1990s researchers found that plasma levels of TNF were much higher in babies who develop the disorder than in age-matched controls.
“We also know if you inject mice with high doses of TNF, you will cause bowel necrosis that looks very much like NEC,” McElroy said.
TNF is a potent inflammatory cytokine that helps to regulate cell survival during normal development. However, in inflammatory diseases such as NEC, TNF increases inside the epithelial cells and induces additional cytokines which set up a perfect storm of inflammation within the epithelium.
This in turn increases membrane permeability, allowing for bacterial invasion into the epithelial cells and eventually into the bowel wall. Once inside the bowel wall, bacteria feed on the infant’s tissues causing fermentation, which produces gas.
Trapped inside the bowel wall, the abnormal air forms a characteristic pattern of pockets that on X-ray films resembles a chain-link fence.
“We as neonatologists can’t pick up this disease until this point. So, by the time we can say a baby has NEC, it already has so much disease process that bacteria has eaten away at the baby’s intestine,” says McElroy. “This leads to necrosis (death) of the bowel.
“But perhaps even more frustrating is that the damage often happens in a pattern similar to leopard markings. You have areas of necrotic lesions all throughout the bowel – not just one section – which makes it difficult for the surgeons to know what areas to remove.”
Only maternal breast milk is known to protect against NEC. Compared to breastfed-only babies, formula-fed infants are six to 10 times more likely to develop NEC, and babies fed both formula and mother’s milk are three times more likely to suffer from the disorder.
“We know breast milk is a very good thing to give these babies. We just don’t know what part of it is such a great thing,” McElroy says.