No abstract

In Argentina, Escherichia coli O157:H7/NM (STEC O157) is the prevalent serotype associated with hemolytic uremic syndrome (HUS), which is endemic in the country with more than 400 cases per year. In order to estimate the prevalence and characteristics of STEC O157 in beef cattle at slaughter, a survey of 1,622 fecal and carcass samples was conducted in nine beef exporting abattoirs from November 2006 to April 2008. A total of 54 samples were found positive for STEC O157, with an average prevalence of 4.1% in fecal content and 2.6% in carcasses. Calves and heifers presented higher percentages of prevalence in feces, 10.5 and 8.5%, respectively. All STEC O157 isolates harbored stx(2) (Shiga toxin 2), eae (intimin), ehxA (enterohemolysin), and fliC(H7) (H7 flagellin) genes, while stx(1) (Shiga toxin 1) was present in 16.7% of the strains. The prevalent (56%) stx genotype identified was stx(2) combined with variant stx(2c (vh-a)), the combination of which is also prevalent (>90%) in STEC O157 post-enteric HUS cases in Argentina. The clonal relatedness of STEC O157 strains was established by phage typing and pulsed-field gel electrophoresis (PFGE). The 54 STEC isolates were categorized into 12 different phage types and in 29 XbaI-PFGE patterns distributed in 27 different lots. STEC O157 strains isolated from 5 of 21 carcasses were identical by PFGE (100% similarity) to strains of the fecal content of the same or a contiguous bovine in the lot. Five phage type-PFGE-stx profiles of 10 strains isolated in this study matched with the profiles of the strains recovered from 18 of 122 HUS cases that occurred in the same period.

We determined the virucidal effectiveness against foot-and-mouth disease virus of the low-temperature long-time cooking of virus-contaminated semitendinosus muscle (ST). Of the 11 time and temperature combinations examined, over a range of 63°C to 75°C for extended periods, the respective processing conditions of 71°C for 10.66 h and 75°C for 5.75 h were virucidal. Samples cooked under these temperature-time combinations were more tender (P<0.01) and had better overall acceptability (P<0.05) than beef cuts cooked by conventional commercial processes currently used in Argentina for meat to be exported. Product yields were increased from 60% for the commercial process to 67.8% or 68.6%, respectively, for the two virucidal thermal processes.