Introduction: Shiga toxin-producing E. coli (STEC) serotype O157:H7 is still considered the main serotype of this group involved in outbreaks of foodborne illnesses. Despite the importance of ground beef as a vehicle for STEC, little is known about their presence in this food sold in Sao Paulo city, SP, Brazil.
Purpose: This study aimed at investigating the presence of STEC in ground beef at retail level in Sao Paulo city, Brazil, characterizing the virulence factors stx1, stx2, eae and ehx and identifying E. coli O157:H7 isolates using the genes uid, rfbO157 and fliCH7.
Methods: 248 samples were acquired at the different districts of Sao Paulo city. Microbiological tests for the detection of STEC were performed following the ISO 16654 methodology for the detection of E. coli O157 serogroup. Suspected colonies were evaluated for the presence of target genes.
Results: One sample (0.4%) of ground beef showed the presence of STEC O157:H7. This isolate carried all investigated virulence factors: stx1, stx2, eae and ehx. Besides the presence of uid, rfbO157 and fliCH7, serotype O157:H7 was also serologically confirmed at Institute Adolfo Lutz. Moreover, the expression of stx genes in Vero cells was also observed.
Significance : This is the first report on the isolation of STEC O157:H7 from ground beef in Brazil showing not only all virulence factors but also expressing Shiga toxin. Therefore, the ingestion of undercooked ground beef can be a risk.