Exfoliating Colitis Associated with Enterotoxigenic Bacteroides Fragilis in a Piglet

Abstract

Bacteroides fragilis is a gram-negative, non-sporeforming, obligately anaerobic bacterium found in high numbers in the intestinal tract of humans and animals. Some isolates of B. fragilis elaborate enterotoxin, which causes fluid accumulation in ligated intestinal loops of calves and lambs. Enterotoxigenic isolates of B. fragilis have been associated with diarrhea1 diseases in calves, lambs, pigs, foals, and humans. Characteristic large intestinal lesions are seen in rabbits and gnotobiotic piglets (Duimstra JR, Collins JE, Myers LL, Benfield DA: 1986, Abstr Conf Res Workers Anim Dis #285, p. 50) experimentally inoculated with human or porcine isolates of enterotoxigenic B. fragilis. Intestinal lesions associated with enterotoxigenic B. fragilis in animals with naturally occurring diarrhea1 disease have not been documented. In this report we describe colonic lesions associated with enterotoxigenic B. fragilis in a piglet with spontaneous diarrhea. An 80-sow swine herd in southeastern Minnesota experienced an epizootic of diarrhea in 2to 17-day-old Yorkshire-Landrace cross piglets. Piglets were kept on plasticcoated wire in raised crates. The breeding herd contained approximately one-third gilts and two-thirds second parity sows. Approximately 90% of the piglets in 13 of 15 litters were diarrheic during a 2-week period; mortality was negligible. A few litters of piglets failed to gain weight and were stunted, but most piglets continued to consume milk and gain weight. A live, robust, well-hydrated, 8-day-old piglet presented for necropsy excreted thick yellow feces at frequent intervals. Necropsy revealed clear edema fluid in the mesentery of the spiral colon, and soft yellow feces adhered to the colonic mucosa. Mesenteric lymphatics contained chyle, and the small intestine did not have lesions. Portions of small and large intestine were immersed in neutral-buffered 10% formalin, embedded in paraffin, sectioned at 4 μm thickness, and stained with hematoxylin and eosin (HE), Gram, and Warthin-Starry stains. Microscopically, the colon mucosa between crypt openings had severe exfoliation of surface mucosal enterocytes (Fig. 1). Clusters of enterocytes often remained attached to the mucosa by a