Shiga toxin-producing Escherichia coli in healthy young beef steers from Argentina: prevalence and virulence properties Lelis Meichtri a , Elizabeth Miliwebsky b , Andrea Gioffre ´ c , Isabel Chinen b , Ariela Baschkier b , Germa ´n Chillemi b , Beatriz E. C. Guth d , Marcelo O. Masana a, * , Angel Cataldi c , H. Ricardo Rodrı ´guez a , Marta Rivas b a Instituto Tecnologı ´a de Alimentos, Centro de Investigacio ´n de Agroindustria, Instituto Nacional de Tecnologı ´a Agropecuaria, Argentina, C.C. 77. C.P. (B1708WAB), Moro ´n, Buenos Aires, Argentina b Servicio Fisiopatogenia, Instituto Nacional de Enfermedades Infecciosas-ANLIS ‘‘Dr. Carlos G. Malbra ´n’’, Ministerio de Salud. Av. Ve ´lez Sarsfield 563, (1281) Buenos Aires, Argentina c Instituto de Biotecnologı ´a, Centro de Investigacio ´n de Ciencias Veterinarias y Agrono ´micas, Instituto Nacional de Tecnologı ´a Agropecuaria, Argentina. Los Reseros y Las Caban ˜as, (1712) Castelar, Buenos Aires, Argentina d Departamento de Microbiologia, Imunologia e Parasitologia, Universidade Federal de Sa ˜o Paulo. Rua Botucatu, 862-3 andar, Vila Clementino, Sa ˜o Paulo, 04023-062 Brazil Received 5 January 2003; received in revised form 10 December 2003; accepted 8 March 2004 Abstract Between July 1999 and December 2000, the prevalence of Shiga toxin-producing Escherichia coli (STEC) was established in 200 Argentine healthy young beef steers (14 – 16 months old) grown under local production systems with a feed grain period of 3 – 4 months, and the STEC strains isolated were examined in regard to their phenotypic and genotypic characteristics. Stool samples (n = 70) and rectal swabs (n = 130) were taken at the slaughterhouse level. By polymerase chain reaction (PCR), Shiga toxin (stx) gene sequences were detected in 69% of the samples. Eighty-six STEC strains were isolated from 39% of the animals. Serogroups identified, in order of frequency, were: O8 (16 strains), O113 (14), O103 (5), O91 (4), O171 (3), O174 (3), O25 (2), O112 (2), O145 (2), O2, O11, O104, O121, O128, O143, O146, O157. The most frequent serotype isolated was O8:H19 (12.9%). A total of 17 serotypes, including E. coli O157:H7 found in one animal (0.5%), have been previously associated with hemolytic uremic syndrome (HUS), bloody and non-bloody diarrhea in different countries, including Argentina. The prevalent genotype isolated was stx2 (51 of 86, 59.3%). Subtyping of stx2 variants showed the prevalence of stx2vh-b (25.6%) and stx2vh-a types (24.4%), and revealed the presence of an atypical stx2-v. Only 7.0% of STEC strains carried eae, and 33.7% harbored EHEC-hlyA gene. The full virulent genotype (stx/eae/EHEC-hlyA) was found to be present in 4 of the 86 (4.7%) STEC strains isolated. This research indicates that young steers from the main beef-producing area of Argentina are an important reservoir of STEC strains; however, its importance as agents of human diseases in our country has still to be established. D 2004 Elsevier B.V. All rights reserved. Keywords: STEC; Beef steers; Prevalence; Virulence 0168-1605/$ - see front matter D 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.ijfoodmicro.2004.03.018 * Corresponding author. Tel.: +54-11-4621-0446/0457; fax: +54-11-4621-2012. E-mail address: mmasana@cnia.inta.gov.ar (M.O. Masana). www.elsevier.com/locate/ijfoodmicro International Journal of Food Microbiology 96 (2004) 189 – 198