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ABSTRACTShigellais one of the major enteric pathogens worldwide. We present a murine model of S. flexneriinfection and investigate the role of zinc deficiency (ZD). C57BL/6 mice fed either standard chow (HC) or ZD diets were pretreated with an antibiotic cocktail and received S. flexneristrain 2457T orally. Antibiotic pre-treated ZD mice showed higher S. flexnericolonization than non-treated mice. ZD mice showed persistent colonization for at least 50 days post-infection (pi). S. flexneri-infected mice showed significant weight loss, diarrhea and increased levels of fecal MPO and LCN in both HC and ZD fed mice. S. flexneripreferentially colonized the colon, caused epithelial disruption and inflammatory cell infiltrate, and promoted cytokine production which correlated with weight loss and histopathological changes. Infection with S. flexneri ΔmxiG(critical for type 3 secretion system) did not cause weight loss or diarrhea, and had decreased stool shedding duration and tissue burden. Several biochemical changes related to energy, inflammation and gut-microbial metabolism were observed. Zinc supplementation increased weight gains and reduced intestinal inflammation and stool shedding in ZD infected mice. In conclusion, young antibiotic-treated mice provide a new model of oral S. flexneriinfection, with ZD promoting prolonged infection outcomes.

ABSTRACTShigella flexneriis a Gram-negative pathogen that invades the colonic epithelium and causes millions of cases of watery diarrhea or bacillary dysentery predominately in children under the age of 5 years in developing countries. The effector Shigellaenterotoxin 2 (ShET2), or OspD3, is encoded by the senor ospD3gene on the virulence plasmid. Previous literature has suggested that ospD3is in an operon downstream of the ospC1gene, and expression of both genes is controlled by a promoter upstream of ospC1. Since the intergenic region is 328 bases in length and contains several putative promoter regions, we hypothesized the genes are independently expressed. Here we provide data that ospD3and ospC1are not co-transcribed and that OspC1 is not required for OspD3/ShET2 function. Most importantly, we identified strong promoter activity in the intergenic region and demonstrate that OspD3/ShET2 can be expressed and secreted independently of OspC1. This work increases our understanding of the synthesis of a unique virulence factor and provides further insights into Shigellapathogenesis.