Whole-genome sequencing (WGS) tests show Listeria strains found in Roos cheese are highly related to those isolated from ill patients, according to an update from the Centers for Disease Control and Prevention (CDC). The results add “further confidence that cheese products produced by Roos Foods were a likely source of the outbreak,” says the CDC.
Normally, a process called pulsed-field gel electrophoresis (PFGE) is used to match outbreak isolates, but WGS provides an even clearer distinction of isolates, according to the CDC. The WGS was performed by the Food and Drug Administration (FDA) and Virginia’s Division of Consolidated Laboratory Services as part of a Listeria WGS initiative that is a collaboration between the CDC, FDA, the U.S. Department of Agriculture, the National Center for Biotechnology Information/National Institutes of Health. The project’s goal is to sequence all US Listeria isolates from sick people and food in as close to real-time as possible.
No new cases have been added since the outbreak was announced in February. Eight people have been sickened, one person has died. All of the case patients are Hispanic. Seven of the cases were in Maryland, the fatality occurred in California. Seven of the patients were hospitalized. Five of the illnesses were related to pregnancy.
