Prevalence, characterization, and genotypic analysis of Escherichia coli O157:H7/NM from selected beef exporting abattoirs of Argentina

M.O.MASANA; G.A. LEOTTA; L.L DEL CASTILLO; B.A D`ASTEK; P.M PALLADINO; L. GALLI; E. VILACOBA; C. CARBONARI; H.R. RODRIGUEZ; M. RIVAS

JOURNAL OF FOOD PROTECTION

INT ASSOC FOOD PROTECTION

Año: 2010 vol. 73 p. 649 - 656

0362-028X

In Argentina, Escherichia coli O157:H7/NM(STECO157)is the prevalents erotype associated with hemolytic uremicsyndrome(HUS),which is endemic in the country with more than 400 cases per year.In order to estimate the prevalence andcharacteristics of STEC O157 in beef cattle at slaughter,as urvey of 1,622 fecal and carcass samples was conducted in nine beefexporting abattoirs from November 2006 to April 2008.A total of 54 samples were found positive for STEC O157,with anaverage prevalence of 4.1% in fecal content and 2.6% in carcasses.Calves and heifers presented higher percentages of prevalencein feces,10.5 and 8.5%,respectively.All STEC O157 isolates harbored stx2 (Shigatoxin2), eae (intimin), ehxA(enterohemolysin),and fliCH7 (H7flagellin)genes,while stx1 (Shigatoxin1)was present in16.7% of  the strains.The prevalent(56%) stx genotype identified was stx2 combined with variant stx2c(vh-a),the combination of which is also prevalent (.90%) inSTEC O157post–enteric HUScases in Argentina.The clonal relatedness of STEC O157strains was established by phagetypingand pulsed-field gel electrophoresis(PFGE).The 54 STEC isolates were categorized into 12 different phagetypes and in 29XbaI-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 phagetype–PFGE–stx profilesof 10 strains isolated in this study matched with the profiles of the strains recovered from 18 of 122 HUS cases that occurred inthe same period.