Characteristics of adherence of enteroaggregative Escherichia coli to human and animal mucosa

Abstract

An Escherichia coli strain (serotype O127a:H2) that had been isolated from a child with diarrhea in Thailand and that was negative for the virulence factors of the four categories of diarrheagenic E. coli (enterotoxigenic, enteropathogenic, enteroinvasive, and enterohemorrhagic) and that showed an aggregative pattern of adherence to HeLa cells was investigated for adherence to native or Formalin-fixed human and animal mucosa. The hemagglutinating activity and adherence ability of the bacteria were resistant to D-mannose and were strictly regulated by environmental conditions. Genetic data supported the close relation between the hemagglutinating activity and adherence ability. In accordance with the adherence pattern on tissue-cultured cells, the bacteria adhered to human and animal mucosa, as evidenced by a direct gold-labeling analysis. In human intestines, Formalin-fixed mucous coatings, epithelial cells of colonic mucosa, epithelial cells of ileal single lymphoid follicles and Peyer's patches, and the absorptive cells of jejunal or ileal villi provided adherence targets. Adherence to M cells in the Peyer's patch-associated epithelium was also confirmed. The adherence levels to native jejunal or ileal human villi were low, as was the case with the corresponding Formalin-fixed villi. In human urinary tract, the superficial epithelial cells of both native and Formalin-fixed ureter provided striking adherence targets. In animal (porcine and rabbit) small intestines, the bacteria adhered to the native villi to a lesser extent than to the Formalin-fixed villi. The adherence levels were compared with those of enterotoxigenic E. coli with colonization factor antigen (CFA)/I pili or CFA/II pili. The data suggested unique mucosa adherence characteristics of the enteroaggregative E. coli strain. The possibility of the adherence ability as a virulence factor was discussed.