Prevalence and characterization of typical and atypical Escherichia coli from fish sold at retail in Cochin, India.
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.
Thampuran
Nirmala
N
Central Institute of Fisheries Technology, Matsyapuri P.O., Cochin-682 029, India. nirmala_varma@yahoo.com
Surendraraj
A
A
Surendran
P K
PK
D000818:Animals; D015169:Colony Count, Microbial; D003257:Consumer Product Safety; D004926:Escherichia coli / Q000254:growth & development* / Q000302:isolation & purification; D019453:Escherichia coli O157 / Q000254:growth & development* / Q000302:isolation & purification; D005399:Fishes / Q000382:microbiology; D005511:Food Handling / Q000379:methods*; D005516:Food Microbiology; D006801:Humans; D007194:India; D017747:Seafood / Q000382:microbiology*