Bacteroides fragilis adherence to Caco-2 cells.

The ability of ten Bacteroides fragilis strains isolated from intestinal and non-intestinal infections, normal flora and environment to adhere to human colon carcinoma cells, Caco-2, was examined. The adherence capacity varied among the strains tested from strongly adherent (76-100%) to non- or weakly adherent (0-25%). Negative staining with Indian ink showed that all the strains were capsulated, although strain 1032 (strongly adherent and originated from bacteremia) had the highest rate of capsulated cells in the culture. All strains studied presented an electron-dense layer and no fimbrial structures in their surface after PTA negative staining. The analysis of the strains with ruthenium red showed the presence of an acidic polysaccharide and also surface vesicles in all of them. The strain 1032 presented an aggregative adherence pattern toward Caco-2 cells monolayers. It could be seen trapped by elongated microvilli and surrounded by extracellular material in the scanning electron microscope. Treatment with sodium periodate (100 mM/1 h) reduced significantly its adherence capacity and also the expression of an electron-dense layer and of the capsule, detected with PTA and Indian ink staining, respectively. We suggest that the capsular polysaccharide might mediate the adherence of the B. fragilis to Caco-2 cells.

The Amazonia variant of Vibrio cholerae: molecular identification and study of virulence genes

The pathogenic O1 Amazonia variant of Vibrio cholerae has been shown previously to have a cytotoxin acting on cultured Vero and Y-1 cells, and to lack important virulence factors such as the cholera toxin (Coelho et al. 1995a). This study extends the molecular analysis of the Amazonia strains, detecting the presence to the toxR gene, with a very similar sequence to that of the El Tor and classical biotypes. The outer membrane proteins are analysed, detecting a variation among the group of Amazonia strains, with three different patterns found. As a by-product of this work a polymerase chain reation fragment was sequenced, reading part of the sequence of the Lon protease of the Amazonia strains. The gene was not previously described in V. cholerae, but its sequences is present in the TIGR database specific for this species.

Preliminary report on the application of the coaggutination test for rapid diagnosis of cholera in the upper Solimöes river area in the Brazilian Amazon region

The conventional diagnosis of cholera depends on complex bacteriological procedures. Coagglutination is a simnple, rapid, inexpensive and efficient technique for the presumptive diagnosis of cholera. Of 840 fecal samples from suspected cases of cholera examined at Tabatinga (State of Amazonas, Brazil) 31 (3.6%) were confirmed by culture and 29 of then were also positive by the coagglutination test performed directly on the fecal enrichment broth (alkaline peptone water). About 90% of the positive coagglutination results were obtained after-5-h incubation at 37 grade C and the sensitivity, specificity and accuracy of the method were 93.5%, 99% and 98.8%, respectively. relative to the culture results, coagglutination yielded two false-negative and eight false-positive results. The coagglutination test for cholera can provide a rapid and reliable tool for epidemiological studies and for the planning of more effective measures against cholera