Prevalence, Characterization, and Genotypic Analysis of Escherichia coli O157:H7/NM from Selected Beef Exporting Abattoirs of Argentina

MASANA MO ; LEOTTA GA; DEL CASTILLO LL; D´ASTEK BA; PALLADINO PM; GALLI L; VILACOBA E; CARBONARI CC; RIVAS M

JOURNAL OF FOOD PROTECTION

INT ASSOC FOOD PROTECTION

Año: 2010 vol. 73 p. 649 - 656

0362-028X

In Argentina, Escherichia coli O157:H7 (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 1622 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 the fecal content, and 2.6% in the carcasses. Calves and heifers presented the higher percentages of prevalence in feces, 10.5 and 8.5%, respectively. All STEC O157 isolates harbored stx2, eae, ehxA and fliCH7 genes, while stx1 was present in 16.7% of the strains. The prevalent (56%) stx-genotype identified was stx2/stx2c(vh-a), 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 11 different phage types (PTs), and in 29 XbaI-PFGE patterns distributed in 27 different lots. STEC O157 strains isolated from five out 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 PT-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.