Diarrheal Disease CausedbyEnterotoxigenic Bacteroides fragilis inInfant Rabbitst

Enterotoxigenic Bacteroides fragilis caused severe,nonhemorrhagic, waterydiarrhea when109CFU ofa porcine or humanisolate was administered orogastrically to3-day-old rabbits. Thebacterium colonized the intestinal tract witha predilection forthelarge intestine (109 CFU/gofcecal contents). Diarrhea occurred at an averageof4.6dayspostinoculation, and84%ofrabbits were deadormoribund atan averageof8.8days postinoculation. Thedisease was characterized bywatery diarrhea anddehydration. Severe histologic lesions including inflammation, exfoliation ofepithelial cells, andcrypthyperplasia were observed throughout the colon. Therewas no indication ofbacteremia or ofbacterial adherence toorinvasion ofintestinal epithelial cells. Rabbits inoculated withnonenterotoxigenic B.fragilis werecolonized withB.fragilis butdidnotdevelop clinical disease orintestinal lesions. Whilethepathogenesis ofthis disease isundefined, clinical signs ofdisease andhistologic changes were consistent witha mechanism ofnetsecretion offluid into thesmall intestine and decreased absorption offluid fromthelarge intestine. Enteric disease caused byenterotoxigenic B.fragilis in infant rabbits was similar tonaturally occurring enteric disease associated withthebacterium inhumansand livestock. Thisstudy established thatenterotoxigenic B.fragilis isenteropathogenic inintact infant rabbits.