Yersinia enterocolitica and Yersinia pseudotuberculosis Detection in Foods
Table 1
Confirmation characteristics of pathogenic Y. enterocolitica and Y. pseudotuberculosis.
Test
Medium
Condition
Characteristic
Reactions
Species
Y. enterocolitica
Y. pseudotuberculosis
The first confirmation test
Urea broth
30°C, 24 h
Urea
+
+
TSI
Slant/column
yellow/yellow
red/yellow
red/yellow
H2S
−
−
−
Gas
−
−
−
LIM
Lysin
−
−
−
Indole
d
−
−
Motility
+,d
+
+
Bile-esculin agar
Esculin
+
−
−
+
The second confirmation test
Pyrazinamidase-test agar
30°C, 48 h
Pyrazinamidase
+
−
−
−
TSB
25°C & 37°C, 24 h
Autoagglutination
−
+
+
+
−
Biotype of Y. enterocolitica
1A
1B
2
3
3 variant VP−
4
3 VP-, S
1, 2, 3, 6
5
4
Genetic group of Y. pseudotuberculosis
Biotyping test
30°C, 48 h
Lipase
+
+
−
−
−
−
−
−
−
−
Indole
+
+
(+)
−
−
−
−
−
−
−
Xylose
+
+
+
+
+
−
+
+
+
+
Voges-Proskauer (VP)
+
+
+
+
−
+
−
−
−
−
Sucrose
+
+
+
+
+
+
−
−
−
−
Differentiation test
Rhamnose
−
−
−
−
−
−
−
+
+
+
Melibiose
−
−
−
−
−
−
−
+
−
−
Serotyping
Others
O:8
O:5, 27 O:9
O:3
O:3
O:3
O:3
O:1 to O:15
O:3
part of O:1, O:5, O:6, O:7, O:9, O:10, O:11, O:12
Pyrazinamidase test is carried out by inoculating a slant of the pyrazinamidase test agar and incubating at 30°C for 48 hours. Then 1 mL of 1% freshly prepared aqueous solution of ammonium ferric sulphate is poured on the slant. After 15 minutes, the reaction is investigated. A brownish pink colour indicates formation of pyrazinic acid and is a positive pyrazinamidase reaction. Autoagglutination test is carried out by inoculating Trypticase soy broth (TSB; BBL) (or MR-VP medium; Difco) and incubating at 25°C and 37°C for 24 hours. The virulent plasmid-positive strain invariably autoagglutinated in TSB when grown at 37°C but did not at 25°C.
