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2. Incidence and
virulence properties of E. coli isolated from
fresh fish and ready-to-eat fish products
- Bhavana Gupta, Sandeep Ghatak and J.P.S. Gill
Vet World. 2013; 6(1): 5-9
Aim: To investigate the incidence and
virulence properties of E. coli in fresh fish and
ready-to-eat fish products from retail markets of
the Ludhiana the present study was conducted.
Materials and Methods: Total of 184 samples
comprising 96 raw fish and 88 ready- to-eat (RTE)
fish products were collected from Ludhiana and
other parts of Punjab and were subjected to
suitable microbiological methods for E. coli
isolation. E. coli isolates were subjected for
haemolytic activity and indicators of plausible
cytotoxicity (lecithinase, protease and gelatinase
production), congo red dye biding assay. To assess
virulence potential isolates were molecularly
screened for stx 1 and 2 genes.
From raw fish samples 47(48.95%), E. coli, were
isolated. From RTE fish products 7(12.96%), E.
coli were isolated. Overall incidence for E. coli
was 54 (29.34%). In vitro virulence
characterization of isolates exhibited that all E.
coli isolates were haemolytic while indicators of
plausible cytotoxicity ( lecithinase, protease and
gelatinase production) were in the range of 16.67%
to 35.19% indicated that though the isolates were
haemolytic they were perhaps less likely to be
cytotoxic. Congo Red binding assay for E. coli
isolates revealed that majority (88.89%) of the
isolates failed to uptake the dye and only few
(11.11%) could bind the dye. Results of serotyping
revealed a total of 15 different serotypes among
the E. coli isolates. More variation was observed
among isolates from raw fish samples (12
serotypes) while RTE fish products harboured only
5 different serotypes. Molecular characterization
of E. coli isolates revealed that PCR screening of
isolates revealed that total 39 (72.22%) samples
out of 54 E. coli isolates were positive for stx1
gene and 28 (51.85%) of isolates were positive for
stx2 gene. Sources wise, 36 (66.66%) of isolates
from raw fish and 3(5.55%) of isolates from RTE
fish products were positive for stx1 while and
stx2 gene could be detected in 24(44.44%) isolates
from raw fish and 4(7.4%) isolates from RTE fish
products.Interestingly, about 20% (37.03%)
isolates were positive for both stx1 and stx2
genes. Among these multivirulent isolates majority
(n=18) belonged to raw fish samples compared to a
few (n=2) from RTE fish products.
The results of the present study highlighted the
possible risks to consumers of fish and fish
products in the region that demand action to
address this public health concern.
E. coli, fish, incidence, ready-to-eat fish
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