Regional differences in attachment of enteroadherent Escherichia coli strain RDEC-1 to rabbit intestine: luminal colonization but lack of mucosal adherence in jejunal self-filling blind loops

Abstract

RDEC-1 (serotype 015:NM) is an enteropathogenic Escherichia coli that adheres to mucosal epithelial cells in the ileum, cecum, and colon, but not in the jejunum, of rabbits during diarrheal illness. As RDEC-1 can adhere to jejunal brush borders in vitro, rapid distal clearing of the enteropathogen from the upper gastrointestinal tract may explain the absence of in vivo adherence of RDEC-1 to rabbit jejunum. To test this hypothesis, self-filling blind loops (SFBL) were created in the jejunum of rabbits that were then inoculated with RDEC-1 to determine if stasis would promote increased luminal colonization and increased mucosal attachment of RDEC-1 in the proximal small intestine. Eight rabbits with SFBL and seven nonoperated littermates were inoculated with RDEC-1 4 weeks after surgery. Semiquantitative estimation of fecal shedding of RDEC-1 and the presence and severity of diarrhea were monitored for 7 days. Rabbits were then killed, and colonization of jejunum and ileum by anaerobic bacteria and luminal colonization of jejunum, ileum, and cecum by RDEC-1 was quantitated. Mucosal adherence of RDEC-1 to jejunum, ileum, and cecum was determined by Giemsa staining of intestinal sections obtained from rabbits with and without SFBL. In addition, brush border membranes (BBM) were prepared from blind loop jejunum, nonoperated jejunum, and ileum. In vitro adherence of RDEC-1 to brush borders was quantitated under phase contrast microscopy. Maximal fecal shedding of RDEC-1 began 3-4 days after infection in all rabbits, but diarrhea was more severe in rabbits with SFBL.(ABSTRACT TRUNCATED AT 250 WORDS)