Research – Recovery Rate of Cells of the Seven Regulated Serogroups of Shiga Toxin-Producing Escherichia coli from Raw Veal Cutlets, Ground Veal, and Ground Beef from Retail Stores in the Mid-Atlantic Region of the United States

Journal of Food Protection

A total of 482 veal cutlet, 555 ground veal, and 540 ground beef samples were purchased from retail establishments in the Mid-Atlantic region of the U.S. over a non-contiguous, two-year period between 2014 and 2017. Samples (325 g each) were individually enriched and screened via real-time PCR for all seven regulated serogroups of Shiga toxin-producing Escherichia coli (STEC). Presumptive STEC positive samples were subjected to serogroup-specific immunomagnetic separation and plated onto selective media. Up to five isolates typical for STEC from each sample were analyzed via multiplex PCR for both the virulence genes (i.e., eae , stx 1 and/or stx 2 , and ehxA ) and serogroup-specific gene(s) for the seven regulated STEC serogroups. The recovery rates of non-O157 STEC from veal cutlets (3.94%, 19 of 482 samples) and ground veal (7.03%, 39 of 555 samples) were significantly higher (P < 0.05) than that from ground beef (0.93%, 5 of 540 samples). In contrast, only a single isolate of STEC O157:H7 was recovered; this isolate originated from one (0.18%) of 555 samples of ground veal. Recovery rates for STEC were not associated with state, season, packaging type, or store type (P > 0.05), but were associated with brand and fat content (P < 0.05). Pulsed-field subtyping of the 270 viable/confirmed STEC isolates from the 64 total samples testing positive revealed 78 pulsotypes (50 to 80% similarity) belonging to 39 pulsogroups, with ≥90% similarity among pulsotypes within pulsogroups. Also, multiple isolates from the same sample displayed an indistinguishable pulsotype for 43 of 64 (67.7%) samples testing positive.  These findings support related data from regulatory sampling exercises over the past decade and confirm that recovery rates for the regulated STEC serogroups are appreciably higher for raw veal compared to raw beef samples as was also observed herein for meat purchased at food retailers in the Mid-Atlantic region of the U.S.

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