Isolation of Shiga toxin-producing Escherichia coli harboring variant Shiga toxin genes from seafood

Abstract

Background and Aim:Shiga toxin-producing Escherichia coli (STEC) are important pathogens of global significance. STEC are responsible for numerous food-borne outbreaks worldwide and their presence in food is a potential health hazard. The objective of the present study was to determine the incidence of STEC in fresh seafood in Mumbai, India, and to characterize STEC with respect to their virulence determinants.Materials and Methods:A total of 368 E. coli were isolated from 39 fresh seafood samples (18 finfish and 21 shellfish) using culture-based methods. The isolates were screened by polymerase chain reaction (PCR) for the genes commonly associated with STEC. The variant Shiga toxin genes were confirmed by Southern blotting and hybridization followed by DNA sequencing.Results:One or more Shiga toxins genes were detected in 61 isolates. Of 39 samples analyzed, 10 (25.64%) samples harbored STEC. Other virulence genes, namely, eaeA (coding for an intimin) and hlyA (hemolysin A) were detected in 43 and 15 seafood isolates, respectively. The variant stx1 genes from 6 isolates were sequenced, five of which were found to be stx1d variants, while one sequence varied considerably from known stx1 sequences. Southern hybridization and DNA sequence analysis suggested putative Shiga toxin variant genes (stx2) in at least 3 other isolates.Conclusion:The results of this study showed the occurrence of STEC in seafood harboring one or more Shiga toxin genes. The detection of STEC by PCR may be hampered due to the presence of variant genes such as the stx1d in STEC. This is the first report of stx1d gene in STEC isolated from Indian seafood.

Recent Updates on Outbreaks of Shiga Toxin-Producing Escherichia coli and Its Potential Reservoirs

“…Numerous studies have reported both O157 and non-O157 STEC in fresh fish and shellfish, and their ready-to-eat products in retail markets (Thampuran et al, 2005;Surendraraj et al, 2010;Prakasan et al, 2018), suggesting that human activities, such as handling, processing, and ingestion of the products might be a major source of STEC contamination. Interestingly, fish and shellfish residing in coastal areas, some cultured fish, and those in close proximity to or downstream of animal livestock facilities have been found to be contaminated with STEC (Gourmelon et al, 2006;Sekhar et al, 2017;Cardozo et al, 2018;Siddhnath et al, 2018;Hussein et al, 2019).…”

Genomic features and antimicrobial resistance patterns of Shiga toxin‐producing Escherichia coli strains isolated from food in Chile

“…The main route of STEC transmission to humans is the consumption of contaminated food, traditionally beef (Kintz et al., 2017). Nevertheless, in recent years there have been increasing reports of illness associated with the consumption of vegetables, seafood, ready‐to‐eat products (RTEP) and other foods (Erickson & Doyle, 2007; Prakasan et al., 2018; Torres et al., 2018).…”

High Prevalence of Multiple Antibiotic-Resistant, Extended-Spectrum β-Lactamase (ESBL)-Producing Escherichia coli in Fresh Seafood Sold in Retail Markets of Mumbai, India

“…Although E. coli is popular as an indicator of faecal contamination of water and foods, it is a significant food-borne human pathogen [1]. Contamination of seafood with E. coli as a consequence of contamination of coastal waters with domestic sewage is common in densely populated countries like India [2,3]. Such pathogenic E. coli can cause a range of infections, such as gastroenteritis, wound infections, septicaemia, urinary tract infections, etc.…”

“…Post-harvest contamination of seafood with E. coli occurs in fish landing centres and markets. Past studies from India have reported the isolation of various pathogroups of E. coli from seafood [ 3 , 17 , 18 , 19 ] and also the presence of highly antibiotic resistant E. coli , such as the bla NDM -harbouring strains [ 20 , 21 , 22 ]. In the study reported here, we investigated the prevalence of antibiotic resistance in Escherichia coli isolated from seafood and the genetic factors responsible for resistance.…”