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Vibrio cholerae O139 Bengal possesses a capsular polysaccharide which may confer increased virulence
A Weintraub1, G Widmalm, P E Jansson
1Karolinska Institute, Department of Immunology, Microbiology, Pathology and Infectious Diseases, Huddinge University Hospital, Sweden.
Abstract:
A newly described Vibrio cholerae serogroup--O139 Bengal, the causative agent of the recent large epidemics of cholera-like disease in the Indian subcontinent and neighbouring countries--possesses a high molecular weight capsular polysaccharide (CPS) that can be visualized by electron microscopy and in composition differs from the lipopolysaccharide (LPS). The CPS and LPS can be separated from each other by a two-step extraction procedure, a phenol-water extraction in order to extract all polysaccharides from the bacterial suspension followed by a phenol-chloroform-petroleum ether (PCP) extraction. The CPS is mainly composed of 3,6-dideoxyhexose (abequose or colitose), quinovosamine and glucosamine. The LPS of the O139 Bengal strain appears to possess a short polysaccharide which contains glucose, galactose, glucosamine and heptose. Both the LPS and CPS are immunogenic. They react in an enzyme immunoassay with rabbit antibodies generated against whole heat-killed bacteria. By analogy with other capsulated bacteria, the possession of a capsule may confer increased virulence of O139 Bengal.
Insights
The O139 Bengal Vibrio cholerae strain has a unique capsular polysaccharide (CPS) and lipopolysaccharide (LPS) that are immunogenic. This capsule may increase the virulence of this cholera-causing bacterium.
Area of Science:
- Microbiology
- Immunology
- Biochemistry
Background:
- Vibrio cholerae O139 Bengal causes widespread cholera-like epidemics.
- This serogroup possesses a distinct high molecular weight capsular polysaccharide (CPS).
- The CPS differs in composition from the lipopolysaccharide (LPS).
Purpose of the Study:
- To characterize the capsular polysaccharide (CPS) and lipopolysaccharide (LPS) of Vibrio cholerae O139 Bengal.
- To investigate the immunogenic properties of CPS and LPS.
- To explore the potential role of the capsule in bacterial virulence.
Main Methods:
- Electron microscopy to visualize CPS.
- Two-step extraction (phenol-water, then phenol-chloroform-petroleum ether) to separate CPS and LPS.
- Compositional analysis of CPS and LPS.
- Enzyme immunoassay (EIA) to assess immunogenicity.
Main Results:
- CPS and LPS were successfully separated and visualized.
- CPS is primarily composed of 3,6-dideoxyhexose, quinovosamine, and glucosamine.
- LPS contains glucose, galactose, glucosamine, and heptose.
- Both CPS and LPS demonstrated immunogenic properties in EIA.
Conclusions:
- Vibrio cholerae O139 Bengal possesses distinct and immunogenic CPS and LPS.
- The presence of a capsule may contribute to the increased virulence of this pathogen.
- Further research into the O139 Bengal strain's virulence factors is warranted.