[A new look at the mechanism of cholera endemicity caused by Vibrio cholerae biotype eltor].
OBJECTIVE
Cholera caused by Vibrio cholerae biotype eltor (EVC) is an endemic disease, subsiding in winter and reappearing in spring and summer. Investigating the state of EVC during the intermittent time is of crucial importance in controlling this disease.


METHODS
Different factors mimicking the internal and external environmental conditions of the host, including human and fish bile, bacterial phages and antibiotics were used experimentally to induce variation in EVC. EVC variants were isolated from the stool of diarrhea patients and river water in old endemic areas during the winter. The variants obtained were tested with gene probe hybridization, DNA restriction enzyme mapping, immunoenzyme staining and animal passaging.


RESULTS
Due to the loss of cell walls, 3 kinds of EVC variants were obtained during induction: the L-form variant, with a complete loss of cell walls; the nonagglutinating variants, with the loss of surface O-antigen; the phage-resistant variants, with the loss of phage receptors. Similar variants were found in field isolation. This variation was proved to be phenotypic, with no change in genetic material: it was reversible and appeared in a seasonal pattern, which coincided with the endemicity of this disease. Passage in animal enhanced this reversion. In compensation for the loss of cell walls, cell membranes were greatly thickened, increasing the ability of the variants to survive during the unfavorable winter conditions.


CONCLUSIONS
EVC varied in a seasonal pattern, coincident with the endemicity of this disease. The compensatory thickening of the cell membranes protects the EVC variants to survive the winter.
Huang
G
G
Department of Microbiology, Bengbu Medical College, Bengbu 233003, China.
Lin
T
T
Jiang
J
J
D002771:Cholera / Q000209:etiology*; D006801:Humans; D014734:Vibrio cholerae / Q000145:classification* / Q000472:pathogenicity / Q000502:physiology