|FENG, PETER - Us Food & Drug Administration (FDA)|
|DELANNOY, SABINE - French Agency For Food, Environmental And Occupational Health & Safety (ANSES)|
|LACHER, DAVID - Us Food & Drug Administration (FDA)|
|Bosilevac, Joseph - Mick|
|FACH, PATRICK - French Agency For Food, Environmental And Occupational Health & Safety (ANSES)|
Submitted to: Meeting Abstract
Publication Type: Abstract Only
Publication Acceptance Date: 6/2/2015
Publication Date: 9/13/2015
Citation: Feng, P., Delannoy, S., Lacher, D., Bosilevac, J.M., Fach, P. 2015. Genetic diversity and virulence potential of Shiga-toxigenic Escherichia coli strains of O113 serogroup isolated from ground beef in the U.S.[Abstract]. Shiga Toxin (Verocytotoxin) Producing Escherichia coli Infections (VTEC) 2015 Conference. Section C, No 4.
Technical Abstract: Introduction: An adherence factor such as intimin is often required for Shiga toxigenic E. coli (STEC) to cause severe diseases. O113:H21 strains do not produce intimin, but have caused HUS in Australia. Analysis of over 4000 ground beef samples in the U.S. found O113:H21 to be the serotype most often identified in ground beef, but, their virulence potential was uncertain as no infection were reported. We characterized O113 isolates from ground beef and compared them to the HUS-causing strains from Australia to determine their virulence potential. The strains were also examined for genetic and clonal diversity. Method: The 59 strains were isolated from ground beef samples in the U.S., but included imported products. A real-time PCR array was used to test for 48 STEC traits. The stx subtype they carried was determined by PCR. Multilocus Sequence Typing (MLST) was used to examine clonal relations and genetic diversity was determined by Clustered Regularly Interspaced Short Palindromic Repeat (CRISPR) typing. Results and Discussion: Except for 9 O113:H4 strains, all others were O113:H21. Stx1a was found in 6/9 O113:H4 strains and these also had 2d alone or with 2a or 2c. None of the O113:H21 strains had Stx1 and most had Stx2a, 2d or both. The O113:H4 strains had similar traits and belonged in the sequence type (ST) 171 clonal group. The O113:H21 strains from beef also had similar traits and were indistinguishable from the pathogenic strains from Australia. All O113:H21 strains were within the STEC-2 clonal group and had ST223, except for 2 strains that had ST820, which is often observed in O113:H21 strains from Australia. The 2 strains with ST820 were isolated from beef samples imported from Australia. CRISPR analysis showed O113:H4 strains to be fairly conserved, while the O113:H21 strains displayed a larger sequence diversity. Implications: The O113:H21 strains from ground beef were indistinguishable from the pathogenic strains suggesting that they may also be pathogenic. Most O113:H21 strains are in the same clonal group, but show a lot of sequence polymorphism among strains.