Direct isolation of Yersinia enterocolitica and Yersinia pseudotuberculosis from meat.

Studies were done to determine the usefulness of dilute alkali (KOH) treatment of meat samples for direct isolation of Yersinia enterocolitica and Yersinia pseudotuberculosis, without enrichment. Virulent Y. enterocolitica and Y. pseudotuberculosis in pork contaminated with 10(2), 10(3), and 10(4) cells per g survived the direct KOH treatment and were never recovered by using KOH postenrichment treatment. From 6 (4.8%) of 125 samples of retail ground pork, four biotype 4 serotype O3 and one biotype 3B serotype O3 strains of Y. enterocolitica and one Y. pseudotuberculosis serotype 4b strain were recovered by using direct KOH treatment without enrichment. As these isolations were attained without using enrichment cultural procedures, they represent an important time-saving alternative to simplify and speed isolation of Yersinia spp. from meat.     

Direct isolation of Yersinia pseudotuberculosis from fresh water in Japan.

Yersinia pseudotuberculosis was recovered from KOH-treated precipitates of 20.6% of 500 freshwater samples. KOH treatment of precipitates is a simple and expedient means of recovering Y. pseudotuberculosis from such samples.     

Direct isolation of Yersinia pseudotuberculosis from fresh water in Japan.

Yersinia pseudotuberculosis was recovered from KOH-treated precipitates of 20.6% of 500 freshwater samples. KOH treatment of precipitates is a simple and expedient means of recovering Y. pseudotuberculosis from such samples.     

Action of sodium chloride on Yersinia pseudotuberculosis and Yersinia enterocolitica

The bacteriostatic and bactericidal action of sodium chloride on 60 Y. pseudotuberculosis strains, 75 Y. enterocolitica strains and 158 urine-fermenting strains has been studied. A new specific feature of Y. pseudotuberculosis has been revealed: high sensitivity to sodium chloride. The suitability of the sodium chloride test has been shown for the identification of Yersinia and the differentiation of Y. pseudotuberculosis and Y. enterocolitica.     

Alkali method for rapid recovery of Yersinia enterocolitica and Yersinia pseudotuberculosis from foods.

A new culture method employing a potassium hydroxide treatment was compared with the conventional cold enrichment method for efficacy in recovering Yersinia sp. from naturally and artificially contaminated food. The new method increased the yield of Yersinia sp. fourfold and the sensitivity 100-fold, shortened the incubation period, and appreciably decreased the growth of non-Yersinia bacteria from a variety of meats, shellfish, and vegetables.     

A cloned chromosomal DNA fragment which differentiates Yersinia pestis from Yersinia pseudotuberculosis and Yersinia enterocolitica

Chromosomal DNA from reference Yersinia strains was digested individually with 9 restriction endonucleases. DNA fragments were separated and analyzed by electrophoresis through agarose gels. The clearest fragment patterns were obtained when EcoRI was employed. The Y. pestis fragment pattern obtained after the use of this enzyme showed the presence of a unique DNA fragment with molecular mass 1400 bp. This DNA fragment was cloned, purified, labeled with 32P and then used to probe EcoRI digests of all three Yersinia species. A strong hybridization signal was obtained with Y. pestis strain. No such signal was found with Y. pseudotuberculosis or Y. enterocolitica. These results indicate that the DNA fragment is species specific and could be used as a diagnostic DNA probe for Y. pestis.     

Distinctive electrophoretic and isoelectric focusing patterns of esterases from Yersinia enterocolitica and Yersinia pseudotuberculosis

Esterases of 53 strains of Yersinia enterocolitica sensu stricto, including five previously defined biotypes, and 30 strains of Yersinia pseudotuberculosis were analysed by horizontal polyacrylamide-agarose gel electrophoresis and by isoelectrofocusing in thin-layer polyacrylamide gel. Esterase bands were defined by their range of activity towards several synthetic substrates, their resistance to heat and to di-isopropyl fluorophosphate. The two species were characterized by distinct electrophoretic patterns of their esterases. The apparent molecular weights of the heat-resistant esterase of Y. enterocolitica and of the major heat-resistant esterase of Y. pseudotuberculosis, as determined by polyacrylamide gradient gel electrophoresis, were estimated to be 52 000 and 250 000, respectively. On the basis of electrophoretic mobilities and isoelectric points of esterases produced by strains of Y. enterocolitica, five principal zymotypes were observed: two for strains of biotype 1, two for strains of biotypes 2 and 3, respectively, and only one for strains of both biotypes 4 and 5. The zymotypes of strains of biotypes 2, 3, 4 and 5 appeared to be more closely related to one another than to zymotypes of strains of biotype 1. Variations in number or mobility of bands observed within each biotype of Y. enterocolitica and within some serotypes of Y. pseudotuberculosis could represent an additional marker for epidemiological analysis.     

The serodiagnosis of human infections with Yersinia enterocolitica and Yersinia pseudotuberculosis

The techniques of sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and immunoblotting were evaluated for the serodiagnosis of human infections with Yersinia enterocolitica and Yersinia pseudotuberculosis. Lipopolysaccharide (LPS) was prepared from strains comprising four serogroups of Y. enterocolitica and five serogroups of Y. pseudotuberculosis, tested against 200 sera submitted to the Laboratory of Enteric Pathogens for routine serodiagnosis, and shown to contain antibodies to Yersinia LPS by agglutination. Forty four sera were found to contain antibodies that bound to one of the LPS preparations used in the immunoassay. Thirty five of the sera contained antibodies to the LPS of Y. enterocolitica O3, whilst three contained antibodies to the LPS of Y. enterocolitica O5, 27 and Y. enterocolitica O9 LPS respectively. Two sera had antibodies to the LPS of Y. pseudotuberculosis II and a single serum contained antibodies to Y. pseudotuberculosis IV. The SDS-PAGE-immunoblotting procedure described proved to be a reliable procedure for the serodiagnosis of infections with Y. enterocolitica and Y. pseudotuberculosis.     

Direct detection and isolation of plasmid-bearing virulent serotypes of Yersinia enterocolitica from various foods.

A procedure was developed for direct detection, isolation, and maintenance of plasmid-bearing virulent serotypes of Yersinia enterocolitica from different food sources. Plasmid-bearing virulent strains of Y. enterocolitica representing five serotypes were simultaneously detected and isolated from enriched swab samples of artificially contaminated pork chops, ground pork, cheese, and zucchini, using Congo red binding and low-calcium-response tests. The method was also effective in isolating plasmid-bearing virulent strains of Y. enterocolitica from naturally contaminated porcine tongues. Virulence of the strains isolated from these foods was confirmed by PCR, the expression of plasmid-associated phenotypes, and mouse pathogenicity.     

Anti-microbial susceptibility of Yersinia pseudotuberculosis and Yersinia enterocolitica under different cultural conditions

Generally, Yersinia pseudotuberculosis and Y. enterocolitica grown at 37°C had increased susceptibility to antibiotics than when grown at 25°C. The susceptibility to kanamycin, cephalothin, tetracycline and chloramphenicol of Yersinia was also influenced by the growth medium and gas composition.N. Markova, T. Radoucheva, L. Ilieva and D. Veljanov are with the Institute of Microbiology, Bulgarian Academy of Science, 1113 Sofia, Bulgaria.     

Characterization of IS1541-like elements in Yersinia enterocolitica and Yersinia pseudotuberculosis

We characterized Yersinia enterocolitica and Yersinia pseudotuberculosis insertion sequences related to insertion sequence 1541, recently identified in Yersinia pestis. For each of the two species, two insertion sequence copies were cloned and sequenced. Genetic elements from Y. pseudotuberculosis were almost identical to insertion sequence 1541, whereas these from Y. enterocolitica were less related. Phylogenetic analysis of the putative transposases encoded by insertion sequences from the three pathogenic members of the genus Yersinia showed that they clustered with those encoded by Escherichia coli and Salmonella enterica elements belonging to the insertion sequence 200/insertion sequence 605 group. Insertion sequences originating from Y. pestis and Y. pseudotuberculosis constitute a monophyletic lineage distinct from that of Y. enterocolitica.     

virF-positive Yersinia pseudotuberculosis and Yersinia enterocolitica found in migratory birds in Sweden

During spring and autumn migrations, 468 fecal samples from 57 different species of migratory birds were collected in Sweden. In total, Yersinia spp. were isolated from 12.8% of collected samples. The most commonly found species was Yersinia enterocolitica, which was isolated from 5.6% of all collected samples, followed by Y. intermedia (3.8%), Y. frederiksenii (3.0%), Y. kristensenii (0.9%), Y. pseudotuberculosis (0.6%), and Y. rohdei (0.4%). The pathogenic, virF-positive Y. pseudotuberculosis strains were recovered from three thrushes. These strains belonged to the same bioserotype, 1/O:2, but had two different profiles as determined by pulsed-field gel electrophoresis with NotI and SpeI enzymes. In addition, 10 Y. enterocolitica strains, all from barnacle geese, belonged to bioserotype 3/O:3, which is associated with human disease. Two of the strains were pathogenic, carrying the virF gene on their plasmids. All pathogenic Y. pseudotuberculosis and Y. enterocolitica strains were recovered during the spring, and as the birds were caught during active migration they likely became infected at an earlier stage of the migration, thus potentially transporting these bacterial pathogens over long geographical distances.     

virF-Positive Yersinia pseudotuberculosis and Yersinia enterocolitica Found in Migratory Birds in Sweden

During spring and autumn migrations, 468 fecal samples from 57 different species of migratory birds were collected in Sweden. In total, Yersinia spp. were isolated from 12.8% of collected samples. The most commonly found species was Yersinia enterocolitica, which was isolated from 5.6% of all collected samples, followed by Y. intermedia (3.8%), Y. frederiksenii (3.0%), Y. kristensenii (0.9%), Y. pseudotuberculosis (0.6%), and Y. rohdei (0.4%). The pathogenic, virF-positive Y. pseudotuberculosis strains were recovered from three thrushes. These strains belonged to the same bioserotype, 1/O:2, but had two different profiles as determined by pulsed-field gel electrophoresis with NotI and SpeI enzymes. In addition, 10 Y. enterocolitica strains, all from barnacle geese, belonged to bioserotype 3/O:3, which is associated with human disease. Two of the strains were pathogenic, carrying the virF gene on their plasmids. All pathogenic Y. pseudotuberculosis and Y. enterocolitica strains were recovered during the spring, and as the birds were caught during active migration they likely became infected at an earlier stage of the migration, thus potentially transporting these bacterial pathogens over long geographical distances.     

Production of thermolabile enterotoxins of Escherichia coli by Yersinia enterocolitica and Yersinia pseudotuberculosis

The plasmids pCG86 and RP4elt coding for thermolabile enterotoxins of Escherichia coli (LT) were transferred in conjugation to Yersinia enterocolitica and Yersinia pseudotuberculosis cells. Both plasmids were stably inherited by the recipient cells. The elt genes of the toxins were expressed in Yersinia cells at the level comparable to the one registered in Escherichia coli cells. In the broth cultures of transconjugant cells the major part of LT toxin is bound with cells (74-97%). The obtained data may serve an experimental basis in favour of possibility of Ent+ strains of Yersinia enterocolitica and Yersinia pseudotuberculosis formation in nature and expediency of search and diagnosing of such strains.