Listeriosis outbreaks in British Columbia, Canada, caused by soft ripened cheese contaminated from environmental sources.

Lorraine Mcintyre,Monika Naus,Lynn Wilcott

doi:10.1155/2015/131623

Lorraine Mcintyre, Monika Naus + Show 1 more

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https://doi.org/10.1155/2015/131623

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Abstract

Soft ripened cheese (SRC) caused over 130 foodborne illnesses in British Columbia (BC), Canada, during two separate listeriosis outbreaks. Multiple agencies investigated the events that lead to cheese contamination with Listeria monocytogenes (L.m.), an environmentally ubiquitous foodborne pathogen. In both outbreaks pasteurized milk and the pasteurization process were ruled out as sources of contamination. In outbreak A, environmental transmission of L.m. likely occurred from farm animals to personnel to culture solutions used during cheese production. In outbreak B, birds were identified as likely contaminating the dairy plant's water supply and cheese during the curd-washing step. Issues noted during outbreak A included the risks of operating a dairy plant in a farm environment, potential for transfer of L.m. from the farm environment to the plant via shared toilet facilities, failure to clean and sanitize culture spray bottles, and cross-contamination during cheese aging. L.m. contamination in outbreak B was traced to wild swallows defecating in the plant's open cistern water reservoir and a multibarrier failure in the water disinfection system. These outbreaks led to enhanced inspection and surveillance of cheese plants, test and release programs for all SRC manufactured in BC, improvements in plant design and prevention programs, and reduced listeriosis incidence.

Highlights

Listeria is an environmentally ubiquitous Gram positive bacterium found in soil and vegetation, sewage, water, animal feeds, and food processing environments [1]
Inspections revealed that the external environments of both dairy processing plants were either neutral or unacceptable, observations supported by test findings of high Listeria spp. and L.m. prevalence in areas outside the dairy processing plant and in the farm environment
Outbreak A events likely resulted from a good manufacturing practices (GMPs) procedural failure arising from incorrect handling practices of culture spray solutions, while outbreak B was attributed to a multibarrier failure in the potable water supply to the plant

Summary

Introduction

Listeria is an environmentally ubiquitous Gram positive bacterium found in soil and vegetation, sewage, water, animal feeds, and food processing environments [1]. The pathogenic species L. monocytogenes (L.m.) infects domestic animals (i.e., cattle, sheep, goats, horses, poultry) and has been found in wild avians, fish, and shellfish [2]. 99% of listeriosis cases are contracted through the consumption of contaminated food [4]. Healthy individuals rarely seek medical care for listeriosis infections, as these are self-limited with gastroenteritis and/or mild flu-like symptoms. Elderly persons (>65 years), immune compromised individuals, neonates, and pregnant women and their fetuses are more susceptible to invasive forms of listeriosis infections, which can lead to encephalitis, meningitis, septicemia, and/or spontaneous abortions during the last trimester of pregnancy. Mortality rates for invasive listeriosis typically range between 20% and 40% [5, 6]

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