Vibrio cholera biotype and serotype
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Vibrio cholerae biotype serotype classification El Tor Classical O1 O139
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Vibrio cholerae - Biotype and Serotype Classification
Serogroups (O Antigen)
V. cholerae is classified into over 200 serogroups based on somatic (O) antigens. Only two serogroups cause epidemic cholera:
| Serogroup | Details |
|---|---|
| O1 | Causes the majority of epidemic and pandemic cholera |
| O139 (Bengal) | Emerged in 1992; also causes epidemic cholera; first identified in Bangladesh/India |
| Non-O1, Non-O139 (NAG vibrios) | Biochemically similar but do not agglutinate in O1 or O139 antisera; do NOT produce cholera toxin and do not cause epidemic cholera |
Biotypes of O1
V. cholerae O1 is further divided into two biotypes:
| Feature | Classical | El Tor |
|---|---|---|
| Pandemic association | 1st–6th pandemics | 7th pandemic (ongoing since 1961) |
| Hemagglutination (chicken/sheep RBCs) | Negative | Positive |
| Resistance to classical phage IV | Sensitive | Resistant |
| Resistance to polymyxin B (50-unit disc) | Sensitive | Resistant |
| Voges-Proskauer (VP) reaction | Negative | Variable (positive historically) |
| Hemolysis | Negative | Positive originally (lost as pandemic progressed) |
| Infection-to-case ratio | Lower | Higher (more inapparent/mild infections) |
| Environmental persistence | Less resistant | More resistant |
| Endemic tendency | Less | Greater |
The El Tor biotype, which was originally hemolytic, lost this property as the pandemic progressed. Currently, cholera is caused mostly by the El Tor biotype and O139.
Serotypes (within O1)
Both Classical and El Tor biotypes are further divided into 3 serotypes based on the O1 antigen composition:
| Serotype | Antigens Present | Notes |
|---|---|---|
| Ogawa | A + B | Most common serotype in India (especially El Tor) |
| Inaba | A + C | Frequently encountered globally |
| Hikojima | A + B + C | Unstable; rarely isolated in pure form |
All three share the A antigen (common to O1). The difference lies in the B and C factor antigens. Serotyping is done by slide agglutination with specific antisera.
Summary Tree
V. cholerae
├── O1 (epidemic)
│ ├── Biotype: Classical
│ │ ├── Serotype: Ogawa
│ │ ├── Serotype: Inaba
│ │ └── Serotype: Hikojima
│ └── Biotype: El Tor
│ ├── Serotype: Ogawa (predominant in India)
│ ├── Serotype: Inaba
│ └── Serotype: Hikojima
├── O139 (Bengal) — epidemic, no biotype subdivision
└── Non-O1, Non-O139 (NAG) — non-epidemic
Key clinical note: The current (7th) pandemic is caused by V. cholerae O1 biotype El Tor. A case study example (Medical Microbiology, 9th ed.) documented V. cholerae O1 biotype El Tor, serotype Inaba causing typical cholera with severe secretory diarrhea. The O139 (Bengal) strain emerged to challenge O1's dominance in 1992 but did not displace El Tor globally.
- Park's Textbook of Preventive and Social Medicine, p. 271
- Medical Microbiology 9e, Case Study chapter
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