FSC-342 Midterm: Lecture 18 - Yersinia

To what bacterial family does Yersinia belong?

Enterobacteriaceae

Is Yersinia Gram positive or Gram negative?

Gram negative

Is Yersinia a facultative anaerobe?

Yes

Is Yersinia oxidase positive or negative?

Oxidase negative

Does Yersinia ferment lactose?

No

How is Yersinia enterocolitica motile?

By peritrichous flagella

Which Yersinia species causes bubonic plague?

Yersinia pestis

Is Yersinia pestis foodborne?

No

What is the natural reservoir of Yersinia pestis?

Rats

How is Yersinia pestis transmitted?

By infected flea bites

What was the fatality rate of bubonic plague between 1990 and 2005?

About 10%

Which Yersinia species is a foodborne pathogen and similar to Y. pestis?

Yersinia pseudotuberculosis

What are the primary reservoirs of Yersinia pseudotuberculosis?

Rodents and birds

Which Yersinia species is most associated with foodborne disease?

Yersinia enterocolitica

Which biovar is commonly isolated in the U.S.?

Biovar 1B ("American strains")

Can Y. enterocolitica grow below 4°C?

Yes, it is psychrotrophic

What is the optimal growth temperature for Y. enterocolitica?

28–30°C

What is the doubling time at 30°C?

~34 minutes

Can Y. enterocolitica survive freezing and thawing?

Yes

Where does Y. enterocolitica survive longer — cooked or raw foods?

Cooked foods

In what types of foods can Y. enterocolitica grow?

Refrigerated meats, vacuum-packed foods, pasteurized products

How quickly can it increase on cooked pork at 25°C?

Within 24 hours

Can Y. enterocolitica grow in seafood and vegetables?

Yes, slowly

Is Y. enterocolitica a good competitor with normal food flora?

No

What is the pH growth range of Y. enterocolitica?

pH 4–10 (optimum 7.6)

How much salt can Y. enterocolitica tolerate?

Up to 5% NaCl

What enzyme does Y. enterocolitica produce to enhance acid tolerance?

Urease

Is Y. enterocolitica inactivated by pasteurization?

Yes

What heat treatment can inactivate Y. enterocolitica?

71.8°C for 18 sec or 62.8°C for 30 min

How effective is heating at 80°C for 10–20 sec?

99.9% reduction

Is Y. enterocolitica sensitive to radiation?

Yes (ionizing and UV)

Is Y. enterocolitica sensitive to organic acids and chlorine?

Yes, though some resistance may occur

What temperatures help control Y. enterocolitica?

Below 4°C

What is an important control strategy after pasteurization?

Avoiding post-pasteurization contamination

Where is Yersinia commonly found in the environment?

Soil, vegetation, lakes, streams, wells

Which animal is the primary reservoir of virulent Y. enterocolitica serovars?

Pigs

What is the main food associated with pathogenic Y. enterocolitica?

Raw or undercooked pork

What is the likely infectious dose of Y. enterocolitica?

Low CFU (exact amount not well defined)

What is a major barrier to infection by Y. enterocolitica?

Gastric acidity

Who is most susceptible to Yersiniosis?

Children under 12, elderly, immunocompromised, malnourished, alcoholics, diabetics

What are common symptoms of Yersiniosis in children?

Diarrhea, low fever, headache, sore throat, abdominal pain

How can Yersiniosis present in older children?

Pseudoappendicitis

How long can Yersiniosis last?

A few days to 3 weeks or more

What symptom may occur in adults?

Pharyngitis

What serious complication can occur in immunocompromised adults?

Bacteremia

What is the fatality rate of Yersinia bacteremia?

30–60%

What foods should be avoided to prevent Yersiniosis?

Raw milk and chitterlings

What is an important kitchen prevention strategy?

Minimizing cross-contamination

What happened in the Pennsylvania Milk Outbreak of 2011?

16 cases from contaminated pasteurized milk due to post-pasteurization contamination

What foods tested positive for Y. enterocolitica in that outbreak?

Ice cream and homemade yogurt

What happened in the Norway Brawn Outbreak of 2006?

Contaminated brawn (pork head meat)

What was the source of a U.S. holiday outbreak of Yersiniosis?

Raw chitterlings cleaned and prepared at home