Public Health Officials Wrap Up Investigation of Outbreak of Listeriosis Linked to Soft Cheeses

Recalled cheeses. Photo courtesy of the CDC

The Centers for Disease Control and Prevention (CDC) collaborated with public health officials in several states and the Food and Drug Administration (FDA) to investigate a multistate outbreak of Listeria monocytogenes infections (listeriosis). Listeria infection can cause a serious, life-threatening illness. This outbreak investigation is over; however, people could continue to get sick because recalled cheeses may still be in homes, restaurants or retail locations.

Five rare DNA fingerprints of Listeria were included in this investigation. Whole genome sequencing showed that the Listeria strains with the five rare DNA fingerprints were closely related genetically.

Thirty people infected with one of the closely related Listeria strainswere reported from 10 states since June 16, 2010. Twenty-eight people were hospitalized. Six illnesses were pregnancy-related; one resulted in a fetal loss. Three deaths were reported from California (2) and Ohio (1).

Epidemiologic and laboratory information indicates that soft cheeses distributed by Karoun Dairies were the likely source of this outbreak. Twenty-one (75%) of 28 ill people with available information reported eating soft cheese in the month before becoming ill. Three of seven ill people who specified a brand of cheese reported brands distributed by Karoun Dairies. No other brand of soft cheese was reported more than once.

The FDA isolated Listeria monocytogenes from two environmental samples collected in September 2015 from the Central Valley Cheese, Inc. manufacturing facility in Turlock, California. Central Valley Cheese, Inc. manufactures cheese for Karoun Dairies. Whole genome sequencing showed that the two isolates were closely related genetically to isolates from ill people. Whole genome sequencing showed that five Listeria isolates collected in 2010 from the same facility were also closely related genetically to isolates from ill people.

On Sept. 16, 2015, Karoun Dairies, Inc. voluntarily recalled 15 types of soft cheeses that the company distributes due to possible contamination with Listeria. Products were sold under the following brands: Karoun, Arz, Gopi, Queso Del Valle, Central Valley Creamery, and Yanni. Products are vacuum packed, in jars or in pails; weights vary from 5 ounces to 30 pounds.

Source: CDC