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Serogroup conversion of Vibrio cholerae
R R Colwell1, A Huq, M A Chowdhury
1University of Maryland Biotechnology Institute, College Park, MD 20740, USA.
Canadian Journal of Microbiology
|October 1, 1995
Summary
Vibrio cholerae non-O1 cells can spontaneously convert to O1 cells in laboratory cultures. This serogroup conversion, detectable after 48 hours, has implications for cholera epidemiology and environmental reservoirs.
Area of Science:
- Microbiology
- Epidemiology
- Environmental Science
Background:
- Vibrio cholerae serogroup O1 is a significant human pathogen, while non-O1 strains are commonly found in the environment.
- O1 strains can exist in a viable but nonculturable state, complicating detection.
- Non-O1 strains are culturable during interepidemic periods in endemic regions.
Purpose of the Study:
- To investigate the occurrence and mechanism of O1 cell emergence in non-O1 V. cholerae cultures.
- To understand the implications of this phenomenon for cholera epidemiology.
Main Methods:
- Immune-fluorescence microscopy to detect O1 cells in non-O1 cultures.
- Laboratory microcosms to study the outgrowth of O1 cells.
- Direct fluorescent-monoclonal antibody staining for O1 cell detection.
- Polymerase chain reaction (PCR) with O-antigen gene probes for genetic analysis.
Main Results:
- O1 cells were detected in pure cultures of V. cholerae non-O1 cells.
- O1 cell outgrowth was observed after 48 hours of incubation, with one O1 cell per 10(6) non-O1 cells detectable.
- PCR analysis revealed homologous genes for the O1 O-antigen in converted non-O1 strains.
- The mechanism likely involves spontaneous mutation or environmental induction of gene expression.
Conclusions:
- V. cholerae non-O1 strains possess the capacity to generate O1 serogroup cells.
- This serogroup conversion has significant implications for understanding cholera transmission and identifying environmental sources of pathogenic V. cholerae O1.