Bacterial Pathogens and Indicators in Pasteurized Goat, Sheep, and Water Buffalo Milk Cheese - April 1, 2019 to March 31, 2023

Food microbiology - Targeted surveys - Final report

Summary

A 4-year targeted survey^Footnote 1 analysed 910 samples of pasteurized goat, sheep, and water buffalo milk cheese for the presence of the pathogens Listeria monocytogenes (L. monocytogenes), Salmonella species (spp.), and Staphylococcus aureus (S. aureus). All samples were also tested for generic Escherichia coli (E. coli) which is an indicator of the hygienic and sanitary conditions of the food supply chain from production to the point of sale.

Almost all (99.8%) of the samples tested were found to be satisfactory. Salmonella spp., L. monocytogenes, and S. aureus at elevated levels were not detected in any of the samples. Generic E. coli at elevated levels was found in 2 of the 910 (0.2%) samples. The Canadian Food Inspection Agency (CFIA) conducted appropriate follow-up activities.

Overall, our survey results indicate that pasteurized goat, sheep, and water buffalo milk cheese sold in Canada are generally safe for consumption. However, as with all food, and especially those that are ready-to-eat (RTE) good hygienic practices are recommended for producers, retailers and consumers.

Why was this survey conducted

The survey was conducted to generate baseline information on the quality and safety of pasteurized goat, sheep, and water buffalo milk cheese sold at retail in Canada. A similar survey^Footnote 2 was conducted from 2018 to 2021, however the samples were not selected based on the animal source. The product types sampled under this survey include soft^Footnote 3, semi-soft^Footnote 3, firm^Footnote 3, and hard^Footnote 3 pasteurized cheeses which are all commonly consumed by Canadians^Footnote 4 of all ages. Unfortunately, many cheeses have been associated with recalls^Footnote 5 and foodborne illness outbreaks^Footnote 6^Footnote 7^Footnote 8 and are considered to be high risk foods.

Contamination with bacterial pathogens can occur at any step in the food supply chain such as during production, processing, packaging, distribution, at retail and/or during preparation for consumption. Consequently, if pathogens are present, there is a potential for foodborne illness as cheeses are RTE.

When was the survey conducted

The survey was conducted over a 4-year period from April 1, 2019 to March 31, 2023.

Where were the samples collected from

Samples were collected from national retail chains and local/regional grocery stores located in the following 11 major cities across Canada:

Halifax
Moncton
Quebec City
Montreal
Toronto
Ottawa
Vancouver
Victoria
Calgary
Saskatoon
Winnipeg

The planned number of samples to be collected from each city was based on the population of the province in which the city was located relative to the total population of Canada.

How many and what kind of samples were collected

A total of 910 pasteurized goat, sheep, and water buffalo cheese samples were collected. A variety of product types were selected to represent a range of moisture content (soft^Footnote 3, semi-soft^Footnote 3, firm^Footnote 3, and hard^Footnote 3 cheeses). A sample consisted of a single or multiple consumer sized packages of the same lot weighing at least 250g.

What were the samples tested for

All samples were tested for L. monocytogenes, Salmonella spp., S. aureus and generic E. coli. L. monocytogenes, Salmonella spp., and S. aureus are pathogenic bacteria while generic E. coli is an indicator of the overall hygienic and sanitary conditions under which the samples have been processed, stored and transported.

What methods were used to tests the samples

Samples were analyzed using analytical methods published in Health Canada's Compendium of Analytical Methods for the Microbiological Analysis of Foods^Footnote 9 that were suitable for the testing of pasteurized cheese.

How were samples assessed

The samples were assessed using criteria based on the principles of the following Health Canada documents: Health Products and Food Branch (HPFB) Standards and Guidelines for Microbiological Safety of Foods – An Interpretive Summary^Footnote 10, Policy on Listeria monocytogenes in Ready-to-Eat Foods^Footnote 11 and the Food and Drugs Act^Footnote 12 (Section 4(1)).

Table 1 - Assessment criteria
Bacteria	Satisfactory	Investigative	Unsatisfactory
L. monocytogenes	Not detected	Not applicable (category 1^{Table Note a}) Detected and ≤ 10² CFU/g (category 2^{Table Note a})	Detected (category 1^{Table Note a}) >10² CFU/g (category 2^{Table Note a})
Salmonella spp.	Not detected	Not applicable	Detected
S. aureus	≤ 10² CFU/g	> 10² and ≤ 10⁴ CFU/g	> 10⁴ CFU/g
Generic E. coli	≤ 10² CFU/g	> 10² and ≤ 2x10³ CFU/g	> 2x10³ CFU/g

No assessment guidelines had been established in Canada for the presence of Salmonella spp. in pasteurized cheese at the time of writing this report. As this bacteria is considered pathogenic to humans it's presence was assessed as unsatisfactory as it is considered to be a violation of the Food and Drugs Act^Footnote 12 Section 4(1)a.

What were the survey results

Over 99.7% of the samples tested were found to be satisfactory. Salmonella spp., L. monocytogenes, and S. aureus (>10² CFU/g) were not detected in any of the samples. Generic E. coli at elevated levels (>10² CFU/g) were found in 2 of the 910 (0.2%) samples.

Table 2 - Assessment results
Bacteria	Number of samples tested	Satisfactory (%)	Investigative (%)
L. monocytogenes	910	908	0
Salmonella spp.			Not applicable
S. aureus			0
Generic E. coli			2^{Table Note b}^{Table Note c}
Total	910	908 (99.8)	2 (0.2)

Survey results are also presented by origin (table 3), production practice (table 4), animal source (table 5), moisture on a fat free basis (MFFB)^Footnote 3 (table 6), and whether the product is ripened or unripened.

Table 3 - Assessment results by product origin
Product origin	Number of samples tested (%)	Satisfactory	Investigative
Domestic	524 (57.6)	524	0
Import	219 (24.1)	217	2
Bulgaria	14	14	0
France	58	58	0
Greece	36	35	1
Israel	1	1	0
Italy	8	7	1
Netherlands	1	1	0
Norway	2	2	0
Spain	86	86	0
United Kingdom	5	5	0
United States	1	1	0
Unknown^{Table Note d}	167 (18.4)	167	0
Total	910	908	2

Table 4 - Assessment results by production practice
Production practice	Number of samples tested (%)	Satisfactory	Investigative
Conventional	896 (98.5)	894	2
Organic	14 (1.5)	14	0
Total	910	908	2

Table 5 - Assessment results by animal source
Animal source	Number of samples tested (%)	Satisfactory	Investigative
Goat	727 (79.9)	727	0
Sheep	118 (13.0)	117	1
Sheep and Goat	17 (1.9)	16	1
Sheep, Goat, and Cow	1 (0.1)	1	0
Water Buffalo	47 (5.2)	47	0
Total	910	908	2

Table 6 - Assessment results by moisture on a fat free basis^Footnote 3
MFFB^Footnote 3	Number of samples tested (%)	Satisfactory	Investigative
Hard (<50%)	37 (4.1)	36	1
Firm (50-62%)	260 (28.6)	260	0
Semi-soft (62-67%)	87 (9.6)	86	1
Soft (67-80%)	526 (57.8)	526	0
Total	910	908	2

Table 7 - Assessment results by ripened vs. unripened
Ripened or Unripened	Number of samples tested (%)	Satisfactory	Investigative
Ripened	361 (39.7)	359	2
Unripened (Fresh)	549 (60.3)	549	0
Total	910	908	2

What do the survey results mean

Previous Canadian^Footnote 2^Footnote 13 and international^Footnote 14 studies on the microbiological quality and safety of retail pasteurized cheeses have shown results approximating those in our study, however no pathogens were detected in any of the samples in the current study. Differing prevalence rates between studies may be attributable to differences in product types tested, methodology, study design, etc.

Overall, our survey results indicate that pasteurized cheese sold in Canada are generally safe for consumption. However, as with all food, and especially those that are RTE good hygienic practices are recommended for producers, retailers and consumers.

What is done with the survey results

All results are used to:

inform risk management decisions
support program design and re-design

The investigative samples triggered appropriate follow-up activities which may have included:

on-site visit of the manufacturer
review of manufacturer production and sanitation practices
review of records and inspection of equipment and establishment conditions

Can I access the survey data

Yes. The data will be accessible on the Open Government Portal.