Public health officials in the USA are investigating a multistate outbreak of Listeria monocytogenes infection that is thought to be associated with the consumption of certain brands of soft cheese distributed by Karoun Dairies Inc..
According to the Centres for Disease Control and Prevention (CDC), the outbreak has affected at least 24 people across nine states since 8 August 2010. Twenty-two people have been hospitalised and one death was reported in Ohio. All the cases so far identified were infected with one of five closely related and rare Listeria strains characterised by genetic fingerprinting.
Epidemiological evidence from interviews with those affected suggests a link with consumption of Karoun Dairies soft cheeses. The FDA has also 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 (WGS) showed that the two isolates are closely related genetically to the outbreak strains. WGS also revealed that five Listeria isolates collected in 2010 from the same facility are also closely related to the outbreak strains.
On 16 September Karoun Dairies voluntarily recalled and ceased production of 15 types of soft cheeses sold nationwide under six different brand names and vacuum packed in jars or pails varying in weight from five ounces to 30 pounds. No samples of the recalled cheeses have yet tested positive for Listeria.
More information about the investigation can be found here.