Prevalence of Non-O157 EHEC in Australian Manufacturing Beef

Introduction: Since 1994, E. coli O157:H7 has been considered an adulterant of raw beef. Whilst E. coli O157:H7 remains the most commonly identified enterohemorrhagic (EHEC) serotype in clinical cases, there is increasing attention on non-O157 EHEC serotypes. FSIS recently broadened the definition of adulterant to include some strains of the serotypes O26, O45, O103, O111, O121 and O145. The term pathogenic Shiga toxin-producing E. coli (pSTEC) has been applied to strains of these serotypes that also harbor stx and eae genes. Australia exports manufacturing beef to the USA and this product will therefore be subject to broadened testing during US import inspection.

Purpose: To determine the prevalence of pSTEC of serotypes O26, O45, O103, O111, O121 and O145 in Australian manufacturing beef.

Methods: Thirty-three Australian beef export abattoirs were sampled in this study. Surface slices of chilled manufacturing beef (1.5 kg) were collected and 375 g sub-samples were tested using one of four different commercial testing systems. Screening tests were performed according to manufacturers’ instructions. All broths from samples that yielded a screening test positive for non-O157 STEC on any test were subjected to confirmatory testing. Confirmation was conducted in accordance, as far as possible, with procedures outlined in FSIS guidebook MLG 5B.01.

Results: Sixty-eight of 2,308 samples screened positive for the presence of non-O157 STEC. The rates of screen positives for individual test methods ranged from 0.7% to 6.9% (mean 2.9%). Non-O157 pSTEC was isolated from 1 (0.04%) sample with O26 the serotype recovered. E. coli of serotypes O26 and O145 harboring eae but not stx were also isolated during the confirmation process.

Significance: The prevalence of non-O157 pSTEC in Australian manufacturing beef appears to be very low. The available screening tests will cause a relatively large proportion of production to be held pending confirmatory tests. These data can be used to further understand appropriate risk management for pSTEC associated with the consumption of beef products.