Adhesion of Vibrio cholerae to Granular Starches

Abstract

Cholera is a severe diarrheal disease caused by specific serogroups of Vibrio cholerae that are pathogenic to humans. Cholera can become epidemic and deadly without adequate medical care. Appropriate rehydration therapy can reduce the mortality rate from as much as 50% of the affected individuals to <1%. Thus, oral rehydration therapy (ORT) is an important measure in the treatment of this disease. To further reduce the symptoms associated with cholera, improvements in oral rehydration solution (ORS) by starch incorporation were suggested. Here, we report that V. cholerae adheres to starch granules incorporated in ORS. Adhesion of 98% of the cells was observed within 2 min when cornstarch granules were used. Other starches showed varied adhesion rates, indicating that starch source and composition play an important role in the interaction of V. cholerae and starch granules. Sugars metabolized by V. cholerae showed a repressive effect on the adhesion process. The possible mechanisms involved are discussed. Comparing V. cholerae adhesion with the adhesion of other pathogens suggests the involvement of starch degradation capabilities. This adhesion to granular starch can be used to improve ORT.

Mechanisms Involved in Governing Adherence of Vibrio cholerae to Granular Starch

“…Therefore, from these results, it appears that the inhibitory effect of M6-ANDS is due to reversible blocking of the starch-binding sites by the maltohexaose sugar residue rather than irreversible blocking of the maltoporin channel. This hypothesis is supported by the low level of inhibition (ϳ15%), which seemed to be due to the low M6-ANDS concentration used (0.01%) compared to the higher sugar concentrations used previously (0.5% to 2%) (15).…”

“…Moreover, when the BATH assay was performed in the presence of 111 mM glucose, there was no effect on adhesion to xylene (data not shown), indicating that a specific adhesion mechanism is involved. An inhibitory effect of low-molecularweight sugars has been demonstrated previously for attachment of V. alginolyticus (36) and V. cholerae (46) to chitin particles, as well as for adhesion of Bifidobacterium (10) and V. cholerae to starch granules (15). However, this is the first time that low-molecular-weight sugars have been used to release adhered V. cholerae cells.…”

“…As we showed previously, low-molecular-weight carbohydrates present in the ORS during adhesion prevent adhesion to starch. Of the sugars tested, those that significantly influenced adhesion of V. cholerae to cornstarch were the sugars that can be utilized by V. cholerae (15). Both yeast extract and tryptone contain some carbohydrates (according to the BD Bionutrients technical manual), explaining the significant reduction in the level of adhesion when the adhesion assay was performed in the presence of LB or spent LB medium (14% and 57%, respectively) (Fig.…”

“…Bacteria often prefer to grow on available surfaces rather than in the surrounding aqueous phase (1,33). V. cholerae is known to adhere to different surfaces, such as the human lumen (20), chironomid egg masses (6), chitin (46), zooplankton (9,18), and cornstarch granules (15). Its ability to adhere is related to the survival of the bacteria in the environment (9), as it facilitates both adherence to available nutrition sources and protection against environmental stresses (52).…”

“…In search of an explanation, we previously demonstrated that V. cholerae strongly adheres to starch granules (15) and suggested that this may explain, at least in part, the beneficial effect of starch-containing ORS in the treatment of cholera compared to treatment with regular ORS. This study was aimed at understanding the mechanisms involved in adhesion of V. cholerae to starch granules.…”