1. Yersinia sp.

2. Characteristics of Yersinia
Enterobacteriaceae family
Morphology, growth characteristics, non-spore forming
Motile? Well, yes and no
~100,000 cases (7th)

3. Taxonomy and classification
11 species
Four pathogens
Y. pestis
Y. pseudotuberculosis
Y. ruckeri
Y. enterocolitica
Serotyping
O:3, O:9, O:5,27
H-typing exists (a,b; b,c; b,c,e,f,k; etc) but is seldom done

4. Biotyping

5. Growth characteristics
Psychrotroph
-1 oC to 40 oC
Heat sensitive
D62.8C in whole milk ~1-60 seconds
Slightly more salt resistant
Grows in 5% salt
pH ~4.0-10; optimum 7.6

6. Reservoirs Zoonoses Large number of wild and domestic animals
Wild rodents
Freshwater ecosystems, soil, rivers, particularly in cool weather
Distribution of specific biotypes/serotypes
Pigs, especially tonsils (biotype 4, also biotype 2)
Wild rodents (?) (biotype 1B; O:8 and O:13a,13b)
Foods of concern: undercooked pork, chitterlings
Animal pathogenic strains exist but are different

8. Outbreaks Location Year # cases Serotype Source New York 1981 159 O:8
Powdered milk/chow mein
Southern US
1982
172
O13a,13b
Pasteurized milk
Chicago
2002 9
O:3
Chitterlings
Norway
2005 11
O:5,27
Brawn
2011 21
O:9
Salad mix PA 7
Not reported
Finland
2014 43
O:1
Raw milk

9. Disease About 104 cfu necessary 3-7 day incubation period
Diarrhea, fever, abdominal pain
Few days to three weeks
Acute mesenteric lymphadenitis, presents as pseudoappendicular syndrome
In rare cases, may have immunological complications
Reactive arthritis
Typically less than three months, prognosis good

10. Take-home points
Y. enterocolitica is species of most concern to food microbiologists
Primary sources are pigs, and possibly rodents; reservoir depends upon serotype
Psychrotrophic
Not terribly resistant to inactivation
Unique disease
Unique phenotypes