Evaluation of isolation methods for pathogenic Yersinia enterocolitica from pig intestinal content.
OBJECTIVE
The aim of this study was to evaluate the efficiency of four isolation methods for the detection of pathogenic Yersinia enterocolitica from pig intestinal content.


RESULTS
The four methods comprised of 15 isolation steps using selective enrichments (irgasan-ticarcillin-potassium chlorate and modified Rappaport broth) and mildly selective enrichments at 4 or 25 degrees C. Salmonella-Shigella-desoxycholate-calcium chloride agar, cefsulodin-irgasan-novobiocin agar were used as plating media. The most sensitive method detected 78% (53/68) of the positive samples. Individual isolation steps using cold enrichment as the only enrichment or as a pre-enrichment step with further selective enrichment showed the highest sensitivities (55-66%). All isolation methods resulted in high numbers of suspected colonies not confirmed as pathogenic Y. enterocolitica.


CONCLUSIONS
Cold enrichment should be used in the detection of pathogenic Y. enterocolitica from pig intestinal contents. In addition, more than one parallel isolation step is needed.


CONCLUSIONS
The study shows that depending on the isolation method used for Y. enterocolitica, the detected prevalence of Y. enterocolitica in pig intestinal contents varies greatly. More selective and sensitive isolation methods need to be developed for pathogenic Y. enterocolitica.
Laukkanen
R
R
 Department of Food and Environmental Hygiene, Faculty of Veterinary Medicine, University of Helsinki, Helsinki, Finland.
Hakkinen
M
M
 Microbiology Unit, Department of Animal Diseases and Food Safety Research, Finnish Food Safety Authority Evira, Mustialankatu, Helsinki, Finland.
Lundén
J
J
 Department of Food and Environmental Hygiene, Faculty of Veterinary Medicine, University of Helsinki, Helsinki, Finland.
Fredriksson-Ahomaa
M
M
 Institute of Food Hygiene and Technology, Faculty of Veterinary Medicine, Ludwig-Maximilians-Universität Munich, Schönleutnerstrasse, Oberschleissheim, Germany.
Johansson
T
T
 Microbiology Unit, Department of Animal Diseases and Food Safety Research, Finnish Food Safety Authority Evira, Mustialankatu, Helsinki, Finland.
Korkeala
H
H
 Department of Food and Environmental Hygiene, Faculty of Veterinary Medicine, University of Helsinki, Helsinki, Finland.
D000818:Animals; D015169:Colony Count, Microbial / Q000379:methods*; D003470:Culture Media; D007422:Intestines / Q000382:microbiology*; D008969:Molecular Sequence Data; D011237:Predictive Value of Tests; D012680:Sensitivity and Specificity; D012703:Serotyping; D013552:Swine / Q000382:microbiology*; D013553:Swine Diseases / Q000382:microbiology; D015008:Yersinia enterocolitica / Q000145:classification / Q000302:isolation & purification*
D003470:Culture Media