Vibrio cholerae non-O1: production of cell-associated hemagglutinins and in vitro adherence to mucus coat and epithelial surfaces of the villi and lymphoid follicles of human small intestines treated with formalin

Virulence factors of clinical isolates of Aeromonas caviae

The mechanism of pathogenicity of 13 Aeromonas caviae strains isolated from fecal specimens of children with diarrhea was examined. Isolates possessed several virulence agents. Six of 13 isolates produced cholera-like toxin, all strains exhibited adhesive ability and secreted catecholate siderophores. Six isolates were able to grow in heat-inactivated serum. Production of hemolysins was not detected. The isolates had relatively high values of LD50 in a mouse model, which suggests that there is no linkage between pathogenicity to mice and the diarrheagenic ability of the isolates.

Rise of cytosolic Ca2+ and activation of membrane-bound guanylyl cyclase activity in rat enterocytes by heat-stable enterotoxin of Vibrio cholerae non-01

The cytosolic calcium level ([Ca2+]i) and the membrane-bound guanylyl cyclase activity in the isolated rat intestinal epithelial cells were investigated. Heat-stable enterotoxin of Vibrio cholerae non-01 (NAG-ST) was found to increase both the [Ca2+]i and the enzyme activity. These changes occur similarly until 5 min of incubation with NAG-ST, indicating that these changes might be involved in NAG-ST induced signal transduction in rat enterocytes.

Epidemic of diarrhea caused by Vibrio cholerae non-O1 that produced heat-stable toxin among Khmers in a camp in Thailand

An epidemic of a cholera-like disease occurred among Khmers in a camp in Aranyaprathet, Thailand, in May 1990. Of 215 patients with diarrhea, Vibrio cholerae O1 was isolated from 25 (12%) and V. cholerae non-O1 was isolated from 15 (7%). Five of 15 (33%) non-O1 V. cholerae isolates hybridized with two different oligonucleotide probes previously used to detect V. cholerae non-O1 that produces a heat-stable toxin. This is the first description of an epidemic of diarrhea caused by V. cholerae non-O1 that produces heat-stable toxin.

Features of cholera and Vibrio parahaemolyticus diarrhoea endemicity in Calabar, Nigeria

The clinical and epidemiological features of acute vibrio diarrhoeal disease were studied in 881 patients seen at the University of Calabar Teaching Hospital (UCTH), Calabar, Nigeria, between January and December 1989. Stools and rectal swabs of patients and randomly-selected control subjects were microscopically and culturally examined for the presence of enteric pathogens. Households of vibrio diarrhoea cases and matched controls were visited for ecologic studies. Of a total of 108 (12.3%) culturally-confirmed bacterial diarrhoeas, 47 (43.5%) were due to Escherichia coli, 33 (30.6%) to Vibrio cholerae-01 (classical and El Tor biotypes) and V. parahaemolyticus, while shigellae and salmonellae accounted for 29 (26.9%) and 9 (8.3%) cases, respectively. Most cholera case households clustered within the ancient neighbourhood of the inner city, characterized by poorly developed water and sewage disposal systems. A preponderance of vibrio diarrhoea patients were children < or = 10 years. Adult cases involved mostly females. The only case of diarrhoea-related death involved an eight-month old child with kwashiorkor and V. parahaemolyticus infection. Incidence of vibrio diarrhoeas was seasonal, with most cases occurring during the dry season followed by subsidence at the onset of rainy season. Bimodal peaks of vibrio diarrhoeal episodes observed over the period appeared to coincide with periods of acute water scarcity, high temperature, increased fishing activities and trade traffic on the Calabar River estuary. Of the environments sampled, only clam shells from a case household and river sediments yielded vibrio pathogens on culture. Ecological factors that are capable of stabilizing a focus of vibrio diarrhoea endemicity in this area are highlighted.

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

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.

Particle agglutination assays to identify fibronectin and collagen cell surface receptors and lectins in Aeromonas and Vibrio species

A rapid particle agglutination assay (PAA) utilizing latex beads coated with connective tissue and serum proteins was evaluated for its ability to identify fibronectin, collagen (types I and IV), fibrinogen, and transferrin cell surface receptors on Vibrio and Aeromonas strains isolated from diseased fish, human infections, and the environment. Similar tests were performed to screen for cell surface lectins. Vibrio as well as Aeromonas strains were found to bind connective tissue proteins (collagen types I, II, and IV and fibronectin), serum proteins (i.e., fibrinogen), and glycoproteins (bovine submaxillary mucin, hog gastric mucin, orosomucoid, and fetuin) immobilized on the latex particles. The specificity of the agglutination reaction was studied by particle agglutination inhibition assays performed by preincubating bacterial suspensions in solutions containing either gelatin (for the various connective tissue protein PAA reagents) or sialic acid-rich glycoproteins (for the various glycoprotein PAA reagents). Expression of cell surface receptors for connective tissue proteins was found to depend on culture methods.

Pili of Vibrio cholerae non-O1

Pili of Vibrio cholerae non-O1 strain S7 were purified and characterized. The pili of S7 were morphologically, electrophoretically, and immunologically (as far as polyclonal antibody was used) indistinguishable from the 16-kilodalton pili of V. cholerae O1 strain 82P7. The purified pili and organisms had D-mannose- and L-fucose-resistant hemagglutinin. The hemagglutinating activity of the purified pili was inhibited by the Fab fraction of antipilus antibody, but the hemagglutinating activity of live organisms was not inhibited completely. The purified pili or Fab fraction of antipilus antibody did not inhibit the adhesion of V. cholerae non-O1 to rabbit intestines. Therefore, the pili were not regarded as a colonization factor of V. cholerae non-O1. A total of 148 V. cholerae non-O1 and O1 clinical isolates were screened for the presence of S7 pili by using an agglutination test with anti-S7 pilus serum; 12 of 49 V. cholerae non-O1 strains and 25 of 99 V. cholerae O1 strains were positive for agglutination. These agglutination reactions were not correlated with adhesion of the organisms to intestines.

Binding of Yersinia enterocolitica to rabbit intestinal brush border membranes, mucus, and mucin

Mucus and its gel-forming glycoprotein component, mucin, are thought to protect the gastrointestinal tract from enteric pathogens by inhibiting their attachment to enterocytes. In this study, we investigated interactions between Yersinia enterocolitica (isogenic strains of virulent and nonvirulent organisms) and crude mucus, highly purified mucin, and brush border membranes (BBMs) isolated from the upper mid-, and distal small intestine and the proximal colon of the rabbit. Adherence of radiolabeled bacteria was assessed to BBMs, mucus, and mucin immobilized in polystyrene microtiter plate wells. Virulent Y. enterocolitica showed saturable binding to mucus, mucin, and BBMs from all four regions of the intestinal tract, although adherence to BBMs was appreciably greater than that to mucus or mucin. Maximal binding of bacteria was higher to BBMs from the distal small intestine and the proximal colon than to those from the upper and mid-small intestine, which may in part explain why the organism localizes to the ileo-caecal regions of the gut. Adherence of virulent Y. enterocolitica to BBMs was significantly reduced in the presence of homologous mucus or mucin preparations. Binding of virulent bacteria appears to depend on plasmid-encoded proteins located on the outer surface membrane, since (i) the isogenic strain lacking the virulence plasmid showed markedly less binding to all BBM, mucus, and mucin preparations; (ii) growth of the virulent strain at 25 degrees C, which inactivates its plasmid, significantly diminished binding to BBMs, mucus, and mucin; and (iii) mild proteolysis substantially decreased adherence of virulent bacteria to BBMs. Compared with rabbit intestinal and colonic mucins, binding of virulent Y. enterocolitica was significantly greater to purified human intestinal mucin and significantly less to rat intestinal mucin. These findings provide support for the role of mucus and mucin in host defense by preventing adherence of virulent Y. enterocolitica to epithelial cell membranes.

Adherence targets of Vibrio parahaemolyticus in human small intestines

Formalin-fixed human small intestinal mucosa with mucus coating, villi, and lymphoid follicle epithelium at the mucosal surface was used to test the adherence sites of clinically isolated (Kanagawa phenomenon-positive) strains of Vibrio parahaemolyticus. V. parahaemolyticus strains grown on CFA agar (supplemented with 3% NaCl) for ca. 3 h at 37 degrees C possessed various levels of cell-associated hemagglutinins (HAs) which were detected with human or guinea pig erythrocytes. The observed adherence abilities of V. parahaemolyticus strains to human small intestinal mucosa correlated roughly with the HA levels of the strains. Under the test conditions, ileal lymphoid follicle epithelium (especially M cells) provided the best adherence target for V. parahaemolyticus. Adherence to villus absorptive cells or to mucus coating was observed at lower levels. In addition, all 3-h-grown V. parahaemolyticus strains tested produced high levels of HAs as detected with rabbit erythrocytes. The strains were all strikingly motile. In contrast, V. parahaemolyticus strains grown on CFA agar (supplemented with 3% NaCl) for ca. 20 h at 37 degrees C had much lower levels of HAs, adherence abilities, and motility. In contrast to the above observations, piliation of V. parahaemolyticus was more extensive at ca. 20 h of incubation at 37 degrees C than at ca. 3 h of incubation at 37 degrees C. The remarkable ability of V. parahaemolyticus to adhere to lymphoid follicle epithelium was also confirmed by using rabbit small intestinal mucosa.