E. coli O157:H7(NM), a specific serotype of Escherichia coli, causes severe intestinal infections in humans and is associated with illnesses such as diarrhea, hemorrhagic colitis, hemolytic uremic syndrome, and in some cases, death. This pathogen was first identified as the cause of a major outbreak linked to undercooked hamburgers in 1982 (Riley et al., 1983) and has continued to cause outbreaks, including the 2024 outbreak associated with onions served at McDonald’s (CDC, 2024). Rapid and accurate characterization of isolates is critical to understanding transmission pathways during food production and processing and to effectively preventing or minimizing pathogen spread through the food chain.
AFL scientists have implemented an improved method for rapid subtyping of E. coli O157:H7 isolates using Multiple-Locus Variable-Number Tandem Repeat Analysis (MLVA) based on eight published loci (Hyytia-Trees et al., 2006, 2010). To enhance method performance, we modified the original primers for more efficient amplification and utilized an ABI 3730XL genetic analyzer for precise fragment sizing, ensuring both accuracy and reproducibility. Validation of the method with 53 E. coli O157:H7 isolates of various sources yielded a combined diversity index of 0.99, demonstrating its high discriminatory power.
In addition to our MLVA typing services for Listeria monocytogenes and Listeria innocua, we now offer MLVA subtyping for E. coli O157:H7. This approach enables food inspection agencies and processing facilities to rapidly and accurately detect subtle genetic differences among isolates, trace potential contamination sources, and take proactive steps to prevent outbreaks – ultimately protecting public health.