Surveillance of soft and semi-soft cheeses for the presence of Listeria spp.

Abstract

Recent outbreaks of listeriosis associated with dairy products prompted a survey to determine the incidence of Listeria in domestic and imported cheeses and to assess the manufacturing practices of the Canadian cheese industry. A total of 374 samples of soft and semi-soft cheeses from 61 Canadian and 98 foreign manufactures were examined for Listeria and for phosphatase. Two samples contained Listeria monocytogenes, and one sample contained Listeria innocua. The three lots of cheese were all manufactured by one plant in France. Thirty-four samples from Canadian and foreign manufactures gave positive phosphatase tests. Additional information confirmed that some of these cheeses were made from unpasteurized milk and were not held 60 days prior to sale. Five of 30 domestic manufactures inspected at the time of sampling were not adhering to good manufacturing practices and were using unpasteurized milk to make cheese. Although Listeria was not found in Canadian cheese, the possibility of a Listeria outbreak occurring in Canada exists if conditions do not improve in a few plants. Continued surveillance by government and industry is recommended in order to ensure the microbiological safety of such cheeses.