Molecular characterization of enterohemorrhagic Escherichia coli hemolysin gene (EHEC- hlyA )-harboring isolates from cattle reveals a diverse origin and hybrid diarrheagenic strains

Background: Quality and microbial safety of milk is demanding day by day as it is considered as a host for pathogenic and spoilage microorganisms. In this study, isolation and molecular characterization of shigatoxigenic O157 and non-O157 Escherichia coli in raw milk marketed in Chittagong, Bangladesh were done on 186 raw milk samples in Bangladesh. Methods: MacConkey agar was initially used to screen for the presence of E. coli and the suspected growth as evidenced by large pink colonies on MacConkey agar. Finally the organism was verified by plating through Eosin Methylene Blue (EMB) agar (a selective medium for E. coli where it produces metallic sheen) and applying standard biochemical tests for E. coli. The presence of virulent genes, Shiga-like toxin (stx1 and stx2), Intimin (eaeA), O157 antigen rfbE and Enterohemorrhagic Escherichia coli (EHEC) Hemolysin (EHEC) hlyA in the contaminating E. coli population was determined by polymerase chain reaction (PCR) run on a thermocycler (Applied Biosystem, 2720 thermal cycler, Singapore). Result: Among the raw milk samples, 33 samples were identified as E.coli positive and among the isolates, 6 (18.18%) were identified as possible EHEC O157 and rest of the isolates (81.82%) were considered as probable non EHEC O157. About, 3.23% (186 samples) EHEC O157 was isolated from raw milk samples. Then all the 33 isolates were taken under PCR assay for the identification of five virulent genes Stx1, Stx2, eaeA, rfbE and hlyA. No virulent genes were found in non- EHEC O157 isolates, but 4 stx2 (66.67%) and 1 hlyA (16.67%) gene were observed in another 4 EHEC O157 isolates out of 6, but one isolates contained the both genes and hence the prevalence of STEC was 2.15% in raw milk. Result indicated poor hygienic standard of raw milk from uncontrolled environments and the increased public health risk of those consuming raw milk from such uncontrolled sources.

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Culture-Based Quantification with Molecular Characterization of Non-O157 and O157 Enterohemorrhagic Escherichia coli Isolates from Rectoanal Mucosal Swabs of Feedlot Cattle

Foodborne Pathogens and Disease ◽

10.1089/fpd.2017.2326 ◽

2018 ◽

Vol 15 (1) ◽

pp. 26-32 ◽

Cited By ~ 2

Author(s):

Zachary R. Stromberg ◽

Gentry L. Lewis ◽

Liesel G. Schneider ◽

Galen E. Erickson ◽

Isha R. Patel ◽

...

Keyword(s):

Escherichia Coli ◽

Molecular Characterization ◽

Feedlot Cattle ◽

Enterohemorrhagic Escherichia Coli

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Enterohemorrhagic Escherichia coli O157: H7 from healthy dairy cattle in Mid-West Brazil: occurrence and molecular characterization

Pesquisa Veterinária Brasileira ◽

10.1590/s0100-736x2014000100004 ◽

2014 ◽

Vol 34 (1) ◽

pp. 24-28 ◽

Cited By ~ 4

Author(s):

Edismauro G. Freitas Filho ◽

Marcos R. A. Ferreira ◽

Jefferson F. N. Pinto ◽

Fabrício R. Conceição ◽

Cecília N. Moreira

Keyword(s):

Escherichia Coli ◽

Dairy Cattle ◽

Molecular Characterization ◽

Enterohemorrhagic Escherichia Coli ◽

Highly Pathogenic ◽

E Coli ◽

Uremic Syndrome ◽

Group D ◽

Virulent Group

Enterohemorrhagic Escherichia coli (EHEC) serotype O157:H7 represents the major Shiga toxin-producing E. coli (STEC) strain related to large outbreaks and severe diseases such as hemorrhagic colitis (HC) and the potentially lethal hemolytic uremic syndrome (HUS). The aim of this study was to report the occurrence and molecular characterization of O157:H7 isolates obtained by rectal swab from 52 healthy dairy cattle belonging to 21 farms in Mid-West of Brazil. Detection of 16SrRNA, stx1, stx2, rfbO157, fliCh7, eae, ehxA, saa, cnf1, chuA, yjaA and TSPE4.C2 genes was performed by PCR. The isolates were further characterized by serotyping. Two hundred and sixty E. coli isolates were obtained, of which 126 were characterized as STEC. Two isolates from the same cow were identified as serotype O157:H7. Both isolates presented the stx2, eae, ehxA, saa and cnf1 virulence factor genes and the chuA gene in the phylogenetic classification (virulent group D), suggesting that they were clones. The prevalence of O157:H7 was found to be 1.92% (1/52 animals), demonstrating that healthy dairy cattle from farms in the Mid-West of Brazil are an important reservoir for highly pathogenic E. coli O157:H7.

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