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Phenotypic and genotypic changes in Vibrio cholerae O139 Bengal
M J Albert1, N A Bhuiyan, K A Talukder
1International Centre for Diarrhoeal Disease Research, Bangladesh, Dhaka. albert@cholera.bangla.net
Journal of Clinical Microbiology
|October 8, 1997
Summary
Vibrio cholerae O139 isolates changed over time, losing traits like CAMP hemolysin and drug resistance. These shifts impact cholera diagnosis and disease severity, with environmental factors likely influencing prevalence.
Area of Science:
- Microbiology
- Epidemiology
- Genetics
Background:
- Vibrio cholerae O139 Bengal caused significant cholera outbreaks in Bangladesh.
- Understanding changes in O139 isolates is crucial for explaining its declining prevalence.
Purpose of the Study:
- To investigate phenotypic and genotypic alterations in V. cholerae O139 isolates from 1993-1996.
- To identify factors contributing to the decline of O139 cholera in Bangladesh.
Main Methods:
- Analysis of V. cholerae O139 isolates for virulence factors (ctx, tcpA, HA/P, capsule, hemolysins) and antimicrobial resistance (O/129, TMP-SMX).
- Genotyping using pulsed-field gel electrophoresis (PFGE).
- Correlation of isolate properties with disease severity (length of hospital stay).
Main Results:
- All isolates possessed key virulence genes (ctx, tcpA), HA/P, and capsule.
- Early isolates were CAMP hemolysin positive and resistant to O/129 and TMP-SMX; later isolates (1996) were negative and susceptible.
- CAMP hemolysin-positive, resistant isolates were associated with more severe disease.
- Four distinct genotypes evolved during the study period.
Conclusions:
- V. cholerae O139 isolates underwent significant phenotypic and genotypic changes.
- Loss of CAMP hemolysin activity and antimicrobial resistance may affect O139 prevalence.
- Environmental factors require further study to understand the competition between V. cholerae O1 and O139.