Prevalence and Characterization of Typical and Atypical Escherichia coli from Fish Sold at Retail in Cochin, India

Abstract

Escherichia coli is a common contaminant of seafood in the tropics and is often encountered in high numbers. The count of E. coli as well as verotoxigenic E. coli O157:H7 was estimated in 414 finfish samples composed of 23 species of fresh fish from retail markets and frozen fish from cold storage outlets in and around Cochin, India. A total of 484 presumptive E. coli were isolated, and their indole-methyl red-Voges-Proskauer-citrate (IMViC) pattern was determined. These strains were also tested for labile toxin production by a reverse passive latex agglutination method and checked for E. coli serotype O157 by latex agglutination with O157-specific antisera. Certain biochemical marker tests, such as methylumbelliferyl-beta-glucuronide (MUG), sorbitol fermentation, decarboxylase reactions, and hemolysis, which are useful for screening pathogenic E. coli, were also carried out. Results showed that 81.4% of the E. coli isolates were sorbitol positive. Among this group, 82% were MUG positive, and 14.46% of the total E. coli isolates showed human blood hemolysis. None of the isolates were positive for agglutination with E. coli O157 antisera nor did any produce heat-labile enterotoxin. This study indicates that typical E. coli O157 or labile toxin-producing E. coli is absent in the fish and fishery environments of Cochin (India). However, the presence of MUG and sorbitol-negative strains that are also hemolytic indicates the existence of aberrant strains, which require further investigation.

Screening of Bacterial and Fungal Biota Associated with Oreochromis niloticus in Lake Manzala and Its Impact on Human Health

“…[41] [42] also found that bacteria belonging to Enterobacteriaceae family were the predominant isolates in the fish samples. [43] found that microbial quality of the tilapia indicated that all tissue samples except muscle tissues were contaminated with fecal coliforms where Escherichia coli is the most common contaminant and is often encountered in high numbers. [44] found that total coliforms count range in fish was between 3.0 × 10 3 -7.5 × 10 6…”

Animal Reservoirs of Shiga Toxin-ProducingEscherichia coli

“…Shellfish, due to their filter feeding ability, pose a significant risk to human infection since they can concentrate and retain pathogens (4,130). Numerous studies have reported the recovery of both O157 and non-O157 STEC from the carcass of fish and shellfish offered for sale (131)(132)(133)(134)(135).…”

<i>Escherichia coli</i> in seafood: A brief overview

“…According to Thampuran et al [26], E. coli is commonly associated with seafood contamination in the tropics, where it is encountered in high numbers. The authors isolated E. coli in finfish samples acquired at the retail market in Cochin (India) and, although typical E. coli O157 or labile toxin-producing E. coli were not detected, the isolation of strains with the ability to produce hemolysis in human blood was a fact worth mentioning.…”