Identification of carriers among individuals recruited in the typhoid registry in Malaysia using stool culture, polymerase chain reaction, and dot enzyme immunoassay as detection tools.

Chronic carriers of Salmonella Typhi act as reservoirs for the organism and become the agents of typhoid outbreaks in a community. In this study, chronic carriers in Kelantan, Malaysia were first identified using the culture and polymerase chain reaction method. Then, a novel serological tool, designated Typhidot-C, was evaluated in retrospect using the detected individuals as control positives. Chronic carriage positive by the culture and polymerase chain reaction method was recorded at 3.6% (4 out of 110) among individuals who previously had acute typhoid fever and a 9.4% (10 out of 106) carriage rate was observed among food handlers screened during outbreaks. The Typhidot-C assay was able to detect all these positive carriers showing its potential as a viable carrier screening tool and can be used for efficient detection of typhoid carriers in an endemic area. These findings were used to establish the first carrier registry for S Typhi carriers in Malaysia.

Chloride secretion induced by thermostable direct haemolysin of Vibrio parahaemolyticus depends on colonic cell maturation.

Vibrio parahaemolyticus produces a thermostable direct haemolysin (TDH) that has been implicated in the pathogenesis of diarrhoeal disease caused by this organism. In previous work, TDH induced Cl- secretion in human colonic epithelial cells that was dependent on the intracellular Ca2+ concentration, [Ca2+]in. This study investigated whether Cl- secretion induced by TDH is influenced by the stage of maturation of intestinal epithelial cells. Two different human colonic cell lines, villus cell-like Caco-2 cells and crypt cell-like T84 cells, cultured by different methods to obtain differentiated samples, were used. When these cells were exposed to butyrate, a transcriptional regulator of differentiation genes, or co-cultured with 18Co cells, a human colonic fibroblast cell line, they showed increased trans-epithelial resistance and villus cell marker enzyme activity. In Caco-2 cells, exposure to butyrate or co-culturing with 18Co cells resulted in increased TDH binding, higher short-circuit currents (Isc) and greater [Ca2+]in. These results suggest that sensitivity to TDH is affected by the stage of cellular differentiation of cultured intestinal epithelial cells.