Background: In 2018, a Shiga toxin-producing Escherichia coli O121 outbreak that affected seven individuals was associated with raw milk Gouda-like cheese produced in British Columbia, Canada.
Objectives: To describe the E. coli O121 outbreak investigation and recommend greater control measures for raw milk Gouda-like cheese.
Methods: Cases of E. coli O121 were identified through laboratory testing results and epidemiologic surveillance data. The cases were interviewed on exposures of interest, which were analyzed against Foodbook Report values for British Columbia. Environmental inspection of the dairy plant and the cheese products was conducted to ascertain a source of contamination. Whole genome multi-locus sequence typing (wgMLST) was performed on all positive E. coli O121 clinical and food isolates at the provincial laboratory.
Results: Four out of the seven cases consumed the same raw milk Gouda-like cheese between August and October 2018. The implicated cheese was aged longer than the required minimum of 60 days, and no production deficiencies were noted. One sample of the implicated cheese tested positive for E. coli O121. The seven clinical isolates and one cheese isolate matched by wgMLST within 6.5 alleles.
Conclusion: Raw milk Gouda and Gouda-like cheese has been implicated in three previous Shiga toxin-producing E. coli outbreaks in North America. It was recommended product labelling to increase consumer awareness and thermization of milk to decrease the risk of illness associated with raw milk Gouda and Gouda-like cheese.
Shiga toxin-producing Escherichia coli (STEC) is a major cause of foodborne illness in North America. STEC infections cause diarrheal illness and may lead to severe complications, such as hemolytic uremic syndrome, and death. The incidence rate of O157 STEC illness has been decreasing, whereas the rate of non-O157 STEC, including O121, has been increasing in many countries, likely due to changes in laboratory methods of detection. Outbreaks of STECO121 have been associated with raw flour, fresh or frozen produce, dairy and beef products
The risk of STEC due to unpasteurized dairy products has been previously described . Between 2002 and 2013, three E. coli O157 outbreaks associated with raw milk Gouda cheeses aged for at least 60 days were reported in North America, including one associated with a British Columbia (BC) dairy plant. Following each outbreak, public health professionals recommended strengthening control measures to decrease the risk associated with raw milk Gouda cheeses . None of these changes had been implemented in Canada by 2018.
In November 2018, another STEC outbreak associated with a raw milk Gouda-like cheese occurred in BC (population: 5.1 million).
The objective of this article is to describe the outbreak investigation and findings and reiterate the need for greater control measures related to raw milk Gouda-like cheese.