ASRB NET and ARS Dairy Pathogens, Toxins & Microbial Risk: practice questions

1 · Listeria monocytogenes in dairy products · medium

Which groups are most at risk of severe listeriosis?

1. People with lactose intolerance
2. Pregnant women, newborns, the elderly and immunocompromised
3. Healthy adult men aged 20 to 40 years who exercise regularly
4. Athletes in training

2 · Salmonella and pathogenic Escherichia coli · easy

Salmonella Dublin is notable because it is:

1. A harmless indicator organism
2. A spore-forming organism that survives UHT treatment of milk
3. Cattle-adapted and frequently multidrug-resistant
4. A strict human pathogen with no animal host

3 · Salmonella and pathogenic Escherichia coli · medium

The large 1985 US salmonellosis outbreak from pasteurised milk was attributed to:

1. Infected milk tanker drivers
2. Salmonella surviving correct pasteurisation of the milk
3. Contaminated packaging
4. A raw-to-pasteurised cross-connection

4 · Campylobacter, Yersinia and Cronobacter · easy

Campylobacter jejuni grows best at:

1. 37 to 42 degrees Celsius
2. 4 to 7 degrees Celsius
3. 20 degrees Celsius only
4. 55 to 60 degrees Celsius

5 · Campylobacter, Yersinia and Cronobacter · medium

Which unusual route has caused Campylobacter outbreaks from pasteurised milk?

1. Contaminated rennet
2. Birds pecking bottle caps
3. Mastitis in goats
4. Spores surviving pasteurisation

6 · Mycobacterium bovis, Brucella and Coxiella: zoonoses carried in milk · medium

Which Brucella species is the most virulent for people?

1. Brucella canis
2. Brucella ovis
3. Brucella melitensis
4. Brucella abortus

7 · Mycotoxins: aflatoxin M1 · medium

The carry-over of aflatoxin B1 into milk as M1 is commonly about:

1. 90 per cent
2. 0.0001 per cent
3. 50 per cent
4. 1 to 3 per cent of ingested B1

8 · Raw milk and raw milk cheese risks · hard

Which raw milk cheeses are regarded as low risk?

1. Soft surface-ripened cheeses eaten young
2. Any raw milk cheese eaten within one week
3. Fresh high-moisture cheeses such as queso fresco made the same day
4. Hard, long-ripened cheeses such as Parmigiano Reggiano

9 · Microbial risk assessment and the ICMSF approach · medium

Using P = 1 - exp(-r x dose) with r = 0.0001, what is the probability of illness from 1,000 cells?

1. About 0.905
2. About 0.001
3. About 0.1 exactly
4. About 0.095

10 · Investigating dairy-borne outbreaks · medium

Of 50 people who drank a milk, 40 became ill; of 50 who did not, 5 became ill. What is the relative risk?

1. 35
2. 4
3. 0.8
4. 8