Evaluation of the performance of the IQ-check kits and the USDA microbiology laboratory guidebook methods for detection of Shiga Toxin-Producing E. coli (STEC) and STEC and Salmonella simultaneously in ground beef

Authors: BARANZONI, GIAN MARCO - Non ARS Employee; Fratamico, Pina; BOCCIA, FEDERICA - The University Of Naples Federico Ii; Bagi, Lori; KIM, GWANGHEE - Non ARS Employee; ANASTASIO, ANIELLO - The University Of Naples Federico Ii; PEPE, TIZIANA - The University Of Naples Federico Ii

Submitted to: Journal of Applied Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/10/2016
Publication Date: 3/1/2017
Publication URL: https://handle.nal.usda.gov/10113/5832863
Citation: Baranzoni, G., Fratamico, P.M., Boccia, F., Bagi, L.K., Kim, G., Anastasio, A., Pepe, T. 2017. Evaluation of the performance of the IQ-check kits and the USDA microbiology laboratory guidebook methods for detection of Shiga Toxin-Producing E. coli (STEC) and STEC and Salmonella simultaneously in ground beef. Journal of Applied Microbiology. 122:809-816.

Interpretive Summary: Foodborne pathogenic bacteria known as Shiga toxin-producing Escherichia coli (STEC) and belonging to types O157:H7, O26, O45, O103, O111, O121, and O145 (often referred to as the top 7 STEC) are responsible for the majority of STEC infections. Cattle are an important reservoir for these pathogens, thus food of bovine origin may be a vehicle for infection with STEC. Thus, these bacteria have been classified as adulterants in meat by the USDA Food Safety and Inspection Service (FSIS). Salmonella is another important foodborne pathogen that is carried by cattle. Rapid and sensitive methods for detection of these pathogens in animal reservoirs and in food are needed to determine their prevalence and to ensure that food contaminated with pathogens does not reach the consumer. The purpose of this study was to evaluate new commercially available real-time polymerase chain reaction (PCR)- (amplification of specific segments of DNA of the pathogens) based kits and compare them to the method currently used for regulatory testing by the USDA to determine their performance for detecting the presence of STEC in ground beef and for detection of co-contamination with STEC and Salmonella in the same ground beef sample. There were no notable differences in results obtained by the commercial methods and the USDA method with all samples artificially contaminated with the pathogen(s). The target pathogens were also able to be recovered from the samples and their identity confirmed. This work showed that the procedure employed using the new commercial kits are simple and rapid and can be used to detect STEC in ground beef, as well as STEC and Salmonella simultaneously, preventing contaminated food from reaching the consumer.

Technical Abstract: Aims: To evaluate the performance of the IQ-Check kits and the USDA Microbiology Laboratory Guidebook (MLG) methods for detection of the top 7 Shiga toxin-producing E. coli (STEC) (O157:H7, O26, O45, O103, O111, O121, and O145) in ground beef and both STEC and Salmonella in co-inoculated samples. Methods and Results: Ground beef samples inoculated with approximately 10 CFU of STEC or both STEC and S. Typhimurium were stored at 4 degrees C for 72 h, followed by testing extracted DNA after 12 and 18 h of enrichment using the IQ-Check and with BAX System kits that are described in the MLG methods. All the samples were positive by PCR screening for both pathogens after 12 and 18 h of enrichment. STEC and S. Typhimurium were isolated on selective agars from all enrichments, with S. Typhimurium isolated after secondary enrichment in Rappaport Vassiladis broth. Conclusion: The IQ-Check and MLG methods were able to detect STEC in ground beef after 12 h of enrichment in samples inoculated with low levels of the pathogen. Both STEC and S. Typhimurium can be detected and isolated in co-inoculated ground beef samples following the different enrichment protocols employed for the IQ-Check and the MLG methods. Significance and Impact of Study: The IQ-Check methods are comparable to the MLG methods for detection of STEC and simultaneous detection of STEC and Salmonella in seeded ground beef after a short enrichment time, thus the IQ-Check method can be useful for the food industry for rapid detection of these pathogens.