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Updated: Jul 19, 2026
Non-Invasive Model of Neuropathogenic Escherichia coli Infection in the Neonatal Rat
Published on: October 29, 2014
Gut-derived bone infection in the neonatal rat
G Steinwender1, G Schimpl, B Sixl
1Department of Pediatric Orthopedics, Karl-Franzens-University Graz, A-8036 Graz, Austria. gerhardt.steinwender@kfunigraz.ac.at
Insights
Formula feeding in newborn rats significantly increases the risk of osteomyelitis by allowing gut bacteria to translocate to the bone. Breast milk protects against this serious bone infection in neonates.
Area of Science:
- Neonatalogy
- Microbiology
- Gastroenterology
Background:
- Osteomyelitis risk is elevated in premature and critically ill neonates.
- The source of bone infection is often unidentified despite potential bacterial entry sites.
Purpose of the Study:
- To investigate the role of bacterial translocation from the intestine in neonatal osteomyelitis.
- To compare bone infection risk between breast-fed and formula-fed rat pups.
Main Methods:
- Newborn Sprague-Dawley rats were divided into breast-fed and formula-fed groups.
- Bacterial analysis of femur, blood, lymph nodes, liver, spleen, and ileum was performed.
- Bacterial translocation and osteomyelitis were assessed using microbiologic procedures.
Main Results:
- Bacterial translocation occurred in 23% of breast-fed rats with no bone infections.
- Formula-fed rats showed elevated ileal bacterial counts and disrupted gut flora.
- All formula-fed rats experienced bacterial translocation, with 77% developing osteomyelitis.
Conclusions:
- Gut bacteria can translocate from the intestine to colonize bone in formula-fed neonates.
- The intestine is a potential origin for osteomyelitis in neonates.
- Breast milk appears protective against formula-associated bacterial translocation and osteomyelitis.
Abstract:
The risk of osteomyelitis is increased in the premature and critically ill neonate. Although potential sites of bacterial entry are present in many of these infants, the source of infection frequently cannot be established. This study was performed to assess the possible role of bacterial translocation from the intestine in the origin of bone infection using models of breast-fed and formula-fed rat pups. Newborn Sprague-Dawley rats suckled either ad libitum by the dam (n = 30), or were fed a rat milk-simulated formula (n = 30). After 3 d, the animals were killed, and the left femur, heart blood, mesenteric lymph nodes, liver, spleen, and terminal ileum were excised. Organs were analyzed for bacteria by standard microbiologic procedures. Bacterial translocation occurred in 23% of breast-fed rats; the bone was not infected in any of these animals. After feeding of formula diet, bacterial counts of the ileum were markedly elevated (p < 0.001), and the composition of the gut flora was disrupted. Bacterial translocation was noted in all formula-fed rats. Bone cultures were positive in 23 of 30 (77%) rats after formula-feeding (p < 0.001 versus breast-feeding). Organisms translocated to the bone included Enterococci, Proteus, Enterobacter, and Escherichia coli. Bacterial species cultured from the bone correlated with the individual colonization pattern of other extraintestinal organs and with the composition of the ileal flora. Members of the gut flora can escape the intestine and colonize the bone in formula-fed rats. The gut should be considered as a potential source for osteomyelitis in the neonate.
