Combined Sarcocystis and gram-positive bacterial infections. A possible cause of segmental enterocolitis in Thailand.

Between 1981 and 1990, 22 intestinal specimens surgically resected due to segmental enterocolitis were collected and examined. Grossly, the specimens were classified into 3 groups 1) Acute inflammation with hemorrhage and necrosis 2) Constrictive lesion 3) False diverticulum with perforation. Mostly, there was unisegmental involvement, distributed in jejunum, ileum and ileocolon. Microscopically, small parasitic structures, interpreted to be unconventional excystation stage of Sarcocystis hominis, (Railliet and Lucet, 1891) Dubey 1976, were present on the luminal border and within the crypt-lining epithelial cells. At the ulcerated area, tissue invasion by Gram-positive bacteria were always seen and considered as second pathogen. Source of the parasite was likely from cyst-containing beef available in markets, (Bos indicus and Bubalus bubalis) along with consumption of undercooked beef. Antismooth muscle antibody, IgG class, with the titer ranging from 1:16-1:256 were detected in 45 per cent of the patients. This is considered as autoimmunity against intestinal smooth muscle damaged previously from subclinical inflammatory condition. Present information suggests a long-standing existence of Sarcocystis in the patients' intestine, associated with Gram-positive bacterial infection, as the mechanism producing segmental enterocolitis found in the Central region.