Exposure to contaminated fish may upsurge the virulent strains of
Vibrio cholerae, the deadly human pathogen in the households of
rural and urban Bangladesh. Since V. cholerae spreading was
reported from the Bay of Bengal, this study hypothesized that
Hilsha (Tenualosa ilisha), a marine and fresh water fish may serve
as a transmission vehicle of potential emerging epidemic causing
strains. For this, we studied 9 toxigenic V. cholerae strains isolated
from Hilsha fish including 6 V. cholerae O1 and 3 non O1/O139
serogroups for virulence associated genotype and their pathogenic
potential on animal model and human cancer cell line .
The V. cholerae O1 and non- O1/O139 strains possessed diverse
virulence genes but lacked some major toxin genes like ctxA, tcp
etc. Eight of the nine strains showed survivability up to 1% sodium
chloride in broth culture which indicates their coastal origin. All
nine isolates were able to accumulate fluid in rabbit ileal loops. Cell
free culture supernatant of three O1 and two non O1 strains
caused distinctive cell death in established HeLa cell line. Diverse
polymorphic patterns were revealed in Random amplified
polymorphic DNA (RAPD) fingerprinting except two non O1 isolates
(I-49d and I-52a) showed considerable correlation in band
patterns. Similar restriction fragment length polymorphism (RFLP)
profile of groEL-I of V. cholerae chromosome 1 in all strains
indicated homogeneity in species level. Hierarchical cluster analysis
by β subunit of RNA polymerase gene (rpoB) sequencing showed
that theses isolates did not cluster together and also distinct from
clinical and environmental toxigenic strains.
Our results indicate the indigenous V. cholerae strains associated
with Hilsha fish possesses considerable virulence potentiality
despite being quite diverse from current epidemic strains.