Putative Virulence Traits and Pathogenicity of Vibrio cholerae Non-O1, Non-O139 Isolates from Surface Waters in Kolkata, India

Abstract

Vibrio cholerae non-O1, non-O139 was isolated from natural surface waters from different sites sampled in diarrhea endemic zones in Kolkata, India. Twenty-one of these isolates were randomly selected and included in the characterization. The multiserogroup isolates were compared by their virulence traits with a group of clinical non-O1, non-O139 isolates from the same geographic area. Of the 21 environmental isolates, 6 and 14 strains belonged to Heiberg groups I and II, respectively. Three of the environmental isolates showed resistance to 2,2-diamine-6,7-diisopropylpteridine phosphate. All of the non-O1, non-O139 strains were positive for toxR, and except for one environmental isolate, none of them were positive for tcpA in the PCR assay. None of the isolates were positive for genes encoding cholera toxin (ctxA), heat-stable toxin (est), heat-labile toxin (elt), and Shiga toxin variants (stx) of Escherichia coli. Additionally, except for one environmental isolate (PC32), all were positive for the gene encoding El Tor hemolysin (hly). The culture supernatants of 86% (18 of 21) of the environmental isolates showed a distinct cytotoxic effect on HeLa cells, and some of these strains also produced cell-rounding factor. The lipase, protease, and cell-associated hemagglutination activities and serum resistance properties of the environmental and clinical isolates did not differ much. However, seven environmental isolates exhibited very high hemolytic activities (80 to 100%), while none of the clinical strains belonged to this group. The environmental isolates manifested three adherence patterns, namely, carpet-like, diffuse, and aggregative adherence, and the clinical isolates showed diffuse adherence on HeLa cells. Of the 11 environmental isolates tested for enteropathogenic potential, 8 (73%) induced positive fluid accumulation (>100) in a mouse model, and the reactivities of these isolates were comparable to those of clinical strains of non-O1, non-O139 and toxigenic O139 V. cholerae. Comparison of the counts of the colonized environmental and clinical strains in the mouse intestine showed that the organisms of both groups had similar colonizing efficiencies. These findings indicate the presence of potentially pathogenic V. cholerae non-O1, non-O139 strains in surface waters of the studied sites in Kolkata.Vibrio cholerae non-serogroup O1 strains are ubiquitous in aquatic environments (35) and have been recognized as the causative agents of sporadic cholera-like disease and outbreaks (5,34,39,43). In addition, environmental nontoxigenic, non-O1 strains play an important role in the evolution of toxigenic V. cholerae (19). However, only a minority of the strains of V. cholerae non-O1 seem to be enteropathogenic. The pathogenicity markers of vibrios are lacking in many species, including V. cholerae non-O1, non-O139 strains. The nature of virulence and the infective doses need to be determined for the establishment of guidelines for risk assessment of each species in surface water and food material earmarked for hu...

The 1.8 Å Cholix Toxin Crystal Structure in Complex with NAD+ and Evidence for a New Kinetic Model

“…Such toxins may allow colonization by nonpathogenic bacteria involved in symbioses. Several non-O1 non-O139 V. cholerae strains have also displayed virulence, indicating that other virulence factors play a role in this pathogenesis (8).…”

Complex secondary metabolites from <i>Ludwigia leptocarpa</i> with potent antibacterial and antioxidant activities

“…These strains are able to produce cholera toxin and hemolysin (24,25). The other strains used in this study were non-O1 and non-O139 strains of V. cholerae (strains CO6 and PC2) (24) and strains of Shigella flexneri (26). The non-O1 and non-O139 strains of V. cholerae were positive for hemolysin production but negative for cholera toxin production (24).…”

“…Among the clinical strains of Vibrio cholerae used in this study, strain NB2 belongs to the O1 serotype and strain SG24(1) belongs to the O139 serotype. These strains are able to produce cholera toxin and hemolysin (24,25). The other strains used in this study were non-O1 and non-O139 strains of V. cholerae (strains CO6 and PC2) (24) and strains of Shigella flexneri (26).…”

“…The other strains used in this study were non-O1 and non-O139 strains of V. cholerae (strains CO6 and PC2) (24) and strains of Shigella flexneri (26). The non-O1 and non-O139 strains of V. cholerae were positive for hemolysin production but negative for cholera toxin production (24). An American Type Culture Collection (ATCC) strain of Staphylococcus aureus, ATCC 25923, was used for quality control.…”

“…Accordingly, compound 3 had significant antibacterial activity against V. cholerae CO6, V. cholerae NB2, V. cholerae PC2, S. flexneri, and S. aureus while compound 6 had significant antibacterial activity against Shigella flexneri SDINT and Staphylococcus aureus ATCC 25923. The strains of V. cholerae NB2, PC2 (24,25) and Shigella flexneri (26) included in the present study were MDR clinical isolates and these were resistant to commonly used drugs such as ampicillin, streptomycin, tetracycline, nalidixic acid, furazolidone, and co-trimoxazole. However, most of the tested samples displayed antibacterial activity against these microbial strains, suggesting that their administration may represent an alternative treatment for V. cholerae, the cause of the dreadful disease cholera, and S. flexneri, the cause of shigellosis.…”