Blog | Wednesday, August 14, 2013

Bacterial outbreak linked to cheese


The Centers for Disease Control and prevention is reporting a multi-state outbreak of Listeriosis linked to a soft-ripened cheese. The cheese is produced by Crave Brothers and was sold at Whole Foods Markets. Only five cases have been reported so far, but this outbreak gives us a few things to think about.

Listeria monocytogenes, the bacterium that causes listeriosis, grows naturally in soil and water, and does not usually cause human disease. It has, though, been linked to outbreaks in humans, and pregnant women, the elderly, and immunocompromised people are especially at risk. Compared to other food-borne illnesses in North America, listeriosis is uncommon, but infections have a high rate of hospitalization, mortality, and fetal loss in infected pregnant women.

Fruits and vegetables have been implicated in outbreaks, but many outbreaks have been linked to soft cheeses such as Brie, Camembert, and queso fresco. In a summary of available data from 2009-2011, pregnant Hispanic women were particularly at risk in outbreaks.

The current outbreak involves specific soft cheeses made by Crave Brothers, a Wisconsin cheese-maker which has voluntarily recalled the implicated food. The company’s website states that the cheeses were made from less-risky pasteurized milk, a fact confirmed in an e-mail exchange with the company.

Even though outbreaks have been linked to cheeses made from pasteurized milk, unpasteurized milk and cheeses made from unpasteurized milk are far more likely to cause listeriosis. Cheeses made from pasteurized milk are far safer.

Raw milk and products made from raw milk have become quite a fad, and listeriosis, a disease that kills infants and the elderly, is closely associated with these products. Pasteurization reduces the risk of listeriosis, with unpasteurized products being 50-160 times more likely to cause the disease. Pregnant women are advised to avoid soft cheeses, and it’s always a good idea to restrict dairy choices to pasteurized products.

Peter A. Lipson, ACP Member, is a practicing internist and teaching physician in Southeast Michigan. After graduating from Rush Medical College in Chicago, he completed his internal medicine residency at Northwestern Memorial Hospital. This post first appeared at his blog at Forbes. His blog, which has been around in various forms since 2007, offers "musings on the intersection of science, medicine, and culture." His writing focuses on the difference between science-based medicine and "everything else," but also speaks to the day-to-day practice of medicine, fatherhood, and whatever else migrates from his head to his keyboard.