Enterobacter sakazakiiEnhances Epithelial Cell Injury by Inducing Apoptosis in a Rat Model of Necrotizing Enterocolitis

Abstract

SUMMARY Necrotizing enterocolitis (NEC) is an inflammatory intestinal disorder that affects 2–5% of all premature infants. Enterobacter sakazakii (ES), a common contaminant in milk-based powdered infant formula, is implicated as a causative agent of sepsis, meningitis, and NEC in newborn infants with high mortality rates. However, the role of ES in the pathogenesis of NEC is not known to date. Here, we demonstrate for the first time that ES is able to induce clinical and histological NEC in newborn rats. ES was found to bind to enterocytes in rat pups at the tips of villi and to intestinal epithelial cells, IEC-6, in culture with no significant invasion. Exposure to ES induced apoptosis and increased the production of interleukin-6 in IEC-6 cells and in the animal model. These data suggest that ES could be a potential pathogen that induces NEC, and triggers intestinal disease by modulating enterocyte intracellular signaling pathways.

Insights into virulence factors determining the pathogenicity ofCronobacter sakazakii

“…100,101 Lipopolysaccarides (LPS) is an outer membrane virulence factor of C. sakazakii, which interacts with enterocytes through LPS mediated binding to TLR4 inducing NEC in animals. [102][103][104][105] In the NEC patients, the elevated level of LPS in serum and stools has been reported. [106][107][108][109][110][111] Altogether, these findings raise the intriguing possibility that LPS may engage in the pathogenesis of NEC and the role of TLR4 within the intestinal epithelium seeks detailed consideration.…”

“…The invasion studies with human intestinal (INT407) cells showed the contribution of Outer membrane protease cpa Provides resistance against bactericidal activity of serum; activates plasminogen and inactivates a2-AP 65,66 Sialic acid utilization nanAKT Confers in pathogenesis 71 Iron acquisition system iuc Encodes an iron-uptake system mediated by the active siderophorethat plays a role in iron transport and regulation 67,73 Efflux system ibeB Encodes copper and silver resistance cation efflux system facilitating invasion of brain microvascular endothelial cells (BMEC) 23 Proteolytic enzymes zpx Cause cell deformation and rounding of cells 83 Lipopoysaccarides Chromosomal encoded genes Disrupt epithelial tight junctions 91,102 Type III hemolysin hly Hemolytic activity 66,90 both microfilaments and microtubules from host and bacterial ompA. [69][70][71] Mittal and co-workers 72 reported that OmpA-positive isolates breach blood-brain barrier and invade central nervous system (CNS) causing clinical manifestations.…”

A Role for cAMP and Protein Kinase A in Experimental Necrotizing Enterocolitis

“…15 A variation of the hyperosmolar formula model supplements lipopolysaccharide into the formula to simulate the bacterial load that is found in neonatal infants who have NEC. 16e19 C. sakazakii has been demonstrated to induce NEC in an experimental rat pup model 20 and has been used to augment both cell and animal models of NEC. 21,22 Furthermore, C. sakazakii resides in the same family (Enterobacteriaceae) which are the most common types of bacteria associated with clinical cultures for patients with NEC.…”

“…21,23,24 Experimentally, C. sakazakii disrupts normal intestinal morphologic characteristics, induces epithelial inflammation, and causes increased apoptosis both in vivo and in IEC-6 cells, a nontransformed rat small intestinal crypt cell line. 20 Therefore, the use of C. sakazakii to induce NEC provides a clinically relevant experimental model.…”

“…25 The C. sakazakii rat pup model of NEC demonstrates increased intestinal epithelial apoptosis. 20 Numerous bacterial factors are associated with increased host cellular apoptosis in disease models. 26 The precise factors that allow C. sakazakii to promote epithelial apoptosis are unknown.…”