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When Food Becomes Dangerous

Linda Seaton
| Oct 16, 2012

We’ve all heard that we need to eat more fruits and vegetables. And really, what could be healthier? The problem is when human pathogens, like Listeria and Salmonella, contaminate the fields or packing facilities where they are processed. Vigilance on the part of health agencies manages to keep our food supply safe, but periodically outbreaks occur.

In 2011, an outbreak of Listeria-contaminated cantaloupes infected 146 people in the United States, killing 30.  The U.S. Centers for Disease Control and Prevention (CDC) employs a national molecular subtyping surveillance system, called PulseNet, to track and contain outbreaks. Using pulse field gel electrophoresis (PFGE) genotyping, public health agencies across the country subtyped the Listeria isolates from the human cases and cantaloupe samples, sending the results to the PulseNet team at the CDC. The outbreak was ultimately tracked to a cantaloupe packaging plant in northeastern Colorado.

listeria samplesAlways looking for a way to improve sample analysis and communication of information during an outbreak, public health agencies are looking into the value next-generation sequencing could play. Recently, a retrospective analysis using Listeria samples from the outbreak was performed using the MiSeq system. Its fast turnaround matched the speed of PFGE and the results were comparable. But it’s the full package that may make the MiSeq an ideal fit for outbreak tracking, i.e. small dimensions (fits into a remote, space-constrained laboratory), higher resolution and accuracy (to identify closely related bacterial isolates), data compatibility with industry-standard, high-throughput systems (the HiSeq family), and an ability to analyze data in a cloud computing environment (for real-time sharing with regional, national, and international public health agencies).