Detection of Shiga Toxin-producing Escherichia coli in Ground Beef: Evaluation of Contamination Levels in Butcheries of The Metropolitan Zone in Asuncion, Paraguay

Shiga toxin-producing Escherichia coli (STEC) can cause from watery diarrhea to severe diseases, such as thrombocytopenic purpura (TP) or hemolytic uremic syndrome (HUS). Ruminants are the main reservoir; most of the time humans are infected through the ingestion of contaminated meat. The goal of this study was the detection of stx1 and stx2 genes through the standardization of a real time PCR method that uses SYBR green, and then we used this method to analyze the presence of STEC in ground beef from butcheries of the metropolitan zone of Asuncion, Paraguay. We analyzed 48 ground beef samples from 24 butcheries. They were processed by standard methods of culture and DNA extraction. Real-time PCR reactions were standardized for the detection of stx1 and stx2. Both genes were detected in the 48 samples studied. The concordance between this method and a conventional PCR technique was excellent, showing kappa concordance indexes of 0.76 for stx1 and 0.87 for stx2. Even though the high levels of contaminated ground beef detected, all the isolates were LEE negatives and O157 negatives, which are less related to outbreaks and severe diseases. The most common virulence profile was stx1/stx2/saa/exhA. With this finding, we have proven the need for preventive procedures in the slaughter process and the handling process of meat products