Microbial safety of cheese in Canada

Abstract

A profile of the microbial safety of cheese in Canada was established based on the analysis of 2955 pasteurized and raw-milk cheeses tested under Canada's National Microbiological Monitoring Program (NMMP) and 2009 raw-milk cheeses tested under the Targeted Survey Program. 97.8% of NMMP and 99.6% of Targeted Survey cheese samples were assessed as being of satisfactory microbiological safety. Under the NMMP, Salmonella spp. was detected in 2 samples, Listeria monocytogenes was detected in 15 samples and no Escherichia coli O157/H7:NM (non-motile) was detected. Cheese samples assessed as having unsatisfactory levels of S. aureus and generic E. coli were found in 18 and 41 samples, respectively. Under the Targeted Survey, L. monocytogenes was detected in 2 samples, while no Salmonella spp. or E. coli O157/H7:NM were detected. Cheese samples assessed as having investigative and unsatisfactory levels of S. aureus were found in 4 and 2 samples respectively. No samples were found to have investigative or unsatisfactory levels of generic E. coli. For cheese samples collected under the NMMP, logistic regression models indicated that contamination was more frequent in raw-milk cheeses compared to pasteurized-milk cheeses (OR = 5.0, 95% CI (3.0, 8.3)), and in imported cheeses compared to domestic cheeses (OR = 8.2, 95% CI (4.1, 16.1)). A statistically significant association was found between cheese samples assessed as having unsatisfactory levels of generic E. coli and detection of L. monocytogenes, Salmonella spp. or levels of S. aureus that were assessed as unsatisfactory (p < .001). These test results will help support risk analysis and inform food safety decisions.

Keywords: E. coli; L. monocytogenes; Raw-milk; S. aureus; Salmonella; Surveillance.