Yersinia pseudotuberculosis in China

Thirty strains of Yersinia pseudotuberculosis were isolated from rabbits (17 strains), wild rats (9 strains) and house rats (4 strains) in China between 1990 and 1993. The biochemical properties of these isolates were identical with those of Y. pseudotuberculosis and no special characteristics were found in these strains. Serologically, serogroups 4b and 5b were identical to isolates found in Japan, and a new serogroup 1c and unclassified strains have also been detected. The existence of virulence-associated properties were different among strains. The pYV plasmid was detected from 6 strains of 30 isolates. This report documents the presence of Y. pseudotuberculosis in China, providing important epidemiological information.     

Intra- and interspecies relatedness ofYersinia pestis by DNA hybridization and its relationship toYersinia pseudotuberculosis

The biochemical characteristics ofYersinia pestis are presented and compared with those ofY. pseudotuberculosis. Motility at 28°C, urease, fermentation of rhamnose, and growth rate on nutrient agar are the best means of separating these organisms. DNA hybridization studies demonstrated thatY. pestis strains are 90% or more interrelated and thatY. pestis andY. pseudotuberculosis are indistinguishable by DNA relatedness. On the basis of DNA data and biochemical and antigenic similarity, these organisms should be treated as two separate subspecies of the same species.Y. pseudotuberculosis was described beforeY. pestis and therefore has priority.Y. pseudotuberculosis subsp.pseudotuberculosis andY. pseudotuberculosis subsp.pestis are recommended as new designations forY. pseudotuberculosis andY. pestis. For medical purposes,Y. pestis andY. pseudotuberculosis can and should continue to be used.     

Biochemical,serological, and phage typing characteristics of 459Yersinia strains isolated from a terrestrial ecosystem

The origins of human contamination withYersinia enterocolitica are still unknown. We have investigated the major components of a terrestrial ecosystem (soil, earthworms, field voles, shrews, crops, hares, rabbits, and birds) for the presence ofYersinia. Four hundred fifty-nine strains ofYersinia were isolated. We report the first isolations of typicalY. enterocolitica belonging to classical or new biotypes and ofY. enterocolitica-like organisms (sucrose negative; rhamnose positive; melibiose and rhamnose positive) from soil samples, earthworms, crops, and birds. Sucrose-negativeY. enterocolitica strains and biotypes 1, 2, and 3, usually associated with human nonmesenteric syndromes, are predominant in soil, which can be considered as a reservoir for these biotypes.Y. enterocolitica serogroups O∶3 and O∶9, strains of which are responsible in Europe for human mesenteric syndromes, were not found in this study. The epidemiology ofY. enterocolitica infections is discussed.     

Yersinia pseudotubetculosis in Italy. Attempted Recovery from 37,666 Samples

From 1981 to 1991, 37,666 human, animal, food and environmental samples were cultured for Yersinia pseudotuberculosis using direct plating methods and/or cold enhancement techniques. Despite an intensive surveillance and adequate culture methods, Y. pseudotuberculosis was isolated from stools of 0.05% (5/9,720) of patients with acute enteritis, and alimentary tracts of 0.1% (10/6,849) of apparently healthy animals. No Y. pseudotuberculosis strains were recovered from stools of 4,726 healthy controls nor from the appendices (656), mesenteric lymph nodes (84), and stools (421) of 656 patients operated for suspected appendicitis. Of the 10,842 food and 4,368 environmental samples, none yielded positive cultures for Y. pseudotuberculosis.     

Comparison of 16S rDNA analysis and rep-PCR genomic fingerprinting for molecular identification of Yersinia pseudotuberculosis

16S rDNA sequence analysis and repetitive element sequence-based PCR (rep-PCR) genomic fingerprinting were evaluated on 11 type strains of the genus Yersinia and 17 recognized serotype strains of Y. pseudotuberculosis to investigate their genetic relatedness and to establish the value of techniques for the identification of Y. pseudotuberculosis. A phylogenetic tree constructed from 16S rDNA sequences showed that the type strains of Yersinia species formed distinct clusters with the exception of Y. pestis and Y. pseudotuberculosis. Moreover, Y. pestis NCTC 5923^T was found to be closely related to Y. pseudotuberculosis serotypes 1b, 3, and 7. Dendrograms generated from REP-PCR, and ERIC-PCR data revealed that members of the genus Yersinia differed from each other with the degree of similarity 62% and 58%, respectively. However, the BOX-PCR results showed that Y. pestis 5923^T clustered with the Y. pseudotuberculosis group with a degree of similarity 74%. According to these findings, 16S rDNA sequence analysis was unable to reliably discriminate Y. pseudotuberculosis from Y. pestis. However, REP-PCR and especially ERIC-PCR provided an effective means of differentiating between members of the taxa. This revised version was published online in June 2006 with corrections to the Cover Date.     

Genomic comparison of Yersinia pestis and Yersinia pseudotuberculosis by combination of suppression subtractive hybridization and DNA microarray

In order to further figure out the genetic differences between Yersinia pestis and Yersinia pseudotuberculosis, and to provide novel insights into the evolution of Y. pestis, we compared the genomes of Y. pseudotuberculosis serogroup I strain ATCC29833 and Y. pestis Antiqua strain 49006 using a combination of suppression subtractive hybridization (SSH) and comparative genomic hybridization with DNAs from a diverse panel of Y. pestis and Y. pseudotuberculosis strains. SSH followed by BLAST analysis revealed 112 SSH fragments specific to strain ATCC29833, compared to the genomic sequence data of Y. pestis strains CO92, KIM and 91001. We identified 17 SSH fragments that appeared to be newly determined genetic contents of Y. pseudotuberculosis. The combination of SSH and microarray analysis showed that the parallel loss of genes contributed greatly not only to the significant genomic divergence between Y. pestis and Y. pseudotuberculosis but also to the intra-species microevolution of both of species. The results confirmed our earlier hypothesis that Y. pestis Antiqua isolates from the natural plague focus B in China represented the most ancestral strains in China, hence phylogenetically the closest isolates to Y. pseudotuberculosis.Electronic Supplementary Material Supplementary material is available to authorised users in the online version of this article at .Xiaoyi Wang and Dongsheng Zhou contributed equally to this work.     

Yersinia ironomics: comparison of iron transporters among Yersiniapestis biotypes and its nearest neighbor, Yersinia pseudotuberculosis

Although Yersinia pestis epidemic biovars and Yersinia pseudotuberculosis are recently diverged, highly related species, they cause different diseases via disparate transmission routes. Since iron transport systems are important for iron acquisition from hosts and for survival in the environment, we have analyzed potential iron transport systems encoded by epidemic and non-epidemic or endemic strains of Y. pestis as well as two virulent Y. pseudotuberculosis strains. Computational biology analysis of these genomes showed a high degree of identity/similarity among 16 proven or possible iron/heme transporters identified. Of these, 7 systems were essentially the same in all seven genomes analyzed. The remaining 9 loci had 2–6 genetic variations among these genomes. Two untested, potential siderophore-dependent systems appear intact in Y. pseudotuberculosis but are disrupted or absent in all the endemic Y. pestis strains as well as the epidemic strains from the antiqua and mediaevalis biovars. Only one of these two loci are obviously disrupted in Y. pestis CO92 (epidemic orientalis biovar). Experimental studies failed to identify a role for hemin uptake systems in the virulence of pneumonic plague and suggest that Y. pestis CO92 does not make a siderophore other than Ybt.     

Characteristics and Pathogenicity of Non-Melibiose-Fermenting Strains of Yersinia pseudotuberculosis O3

The biological properties of non-melibiose-fermenting (NMF) strains of Yersinia pseudotuberculosis 03 were investigated. These strains were clearly distinguished from representative melibiose-fermenting (MF) strains of Y. pseudotuberculosis 03 by their pathogenicity in mice, sensitivity to some phages, production of catalase, restriction endonuclease analysis of virulence plasmid DNA with BamHI, detection of specific yersinia outer-membrane proteins with SDS-PAGE, antigenicity of the outer-membrane proteins and neutrophil resistance to phagocytosis. The pathogenicity of NMF strains was clearly less than that of MF strains. In addition, the resistance of NMF strains to phagocytosis and catalase activity was evidently weaker than that of MF strains. These results suggested that the difference of pathogenicity was due to the ability of catalase production. Although the relationship between the above characteristics and melibiose-fermentation was not analysed, the pathogenicity of Y. pseudotuberculosis 03 strains can probably be predicted by testing melibiose-fermentation and catalase production.     

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.     

Serological analysis of eleven strains ofRhizobium japonicum

The present communication reports a serological analysis of eleven strains ofRhizobium japonicum. The slow-diffusing thermostable antigens were found to be suitable for the basic differentiation of the somatic serogroups inRhizobium japonicum. One to three precipitation bands of the slow-diffusing thermostable antigens, one to two bands of the fast-diffusing thermostable antigens and one to three bands of the thermolabile antigens were detectable in the whole cell cultures ofR. japonicum by means of the immunodiffusion technique. Two basic somatic serogroups were differentiated on the basis of the slow-diffusing thermostable antigens. The thermolabile antigens were identical in most of the strains.The author is greatly indebted to Mrs. M. Kabelovà for technical assistance.This investigation forms part of a contribution prepared by the Czechoslovak National Committee for the International Biological Programme (Section PP: Production Processes).     

Two strains ofVibrio cholerae non-O1 possessing somatic (O) antigen factors in common withV. cholerae serogroup O139 synonym “Bengal”

Two strains (O22 reference strain, 169–68, and strain 490–93 isolated from a patient with diarrhea in Thailand) ofVibrio cholerae non-O1 possessing somatic (O) antigen factors in common withV. cholerae O139 synonym Bengal are described. The O antigens of these two strains were closely related to that ofV. cholerae O139 in an a,b-a,c type of relationship, but were not completely identical with serogroup O139. Therefore, both these strains are not classified into the O139 serogroup ofV. cholerae, because they have their own major antigens. As the strain 490–93 could not be placed into any of the 154 established O serogroups ofV. cholerae, this strain was assigned to a new serogroup, O155. For practical use, the diagnostic antiserum prepared against the O139 reference strain (MO45, ATCC 51394) ofV. cholerae must be absorbed with reference strains 169–68 and 490–93 representing serogroups O22 and O155 ofV. cholerae to remove cross-reacting agglutinins of the O22 and O155 strains, respectively.     

Enterotoxin production at refrigeration temperature byYersinia enterocolitica andYersinia enterocolitica-like bacteria

Enterotoxin production after cultivation for 7 days in a refrigerator (3–6°C) was indicated for 4 of 20 strains ofYersinia enterocolitica andY. enterocolitica-like bacteria, by use of the infant mouse assay. These four strains were isolated from wild-living small mammals and water. Three of these isolates (Y. kristensenii, serogroups 11 and 28) were enterotoxigenic at 22 and 37°C as well as at refrigeration temperature. The remaining strain (Y. enterocolitica sensu stricto, serogroup 6) produced enterotoxin only at refrigeration temperature and at 22°C. The results indicate thatY. enterocolitica andY. enterocolitica-like bacteria may be capable of causing food intoxication after food storage at refrigeration temperature. A potential clinical significance of theY. enterocolitica enterotoxin in cold-blooded animals such as fish is suggested.     

Biochemical heterogeneity of serotype 03 strains of 700Yersinia strains isolated from humans,other mammals,flies, animal feed,and river water

A total of 700 serotype 03 strains of yersiniae were recovered from patients, households withYersinia enterocolitica-infected persons, healthy humans, pigs, dogs, flies, feed, and river water, from 1977 to 1983. Of these isolates, 695 belonged toYersinia enterocolitica, three toYersinia intermedia, and two toYersinia frederiksenii. The 695Y. enterocolitica strains were classified into 484 biotype 4 serotype 03 phage type VIII, 17 biotype 4A (ornithine decarboxylase-negative) serotype 03 phage type VIII, 15 biotype 4B (maltosenegative) serotype 03 phage type VIII, and 179 biotype 3B (VP-, sorbose-, and inositolnegative) serotype 03 phage type II. These four biochemical heterogeneous types, including three new types, ofY. enterocolitica probably have long existed in Japan. There was a close relation between human infection withY. enterocolitica and the harboring ofY. enterocolitica in pigs and dogs.     

Yersinia spp. in surface water in San Luis,Argentina

Yersinia spp. was examined in three rivers and two lakes located in the Province of San Luis, Argentina, over a 1-year period. Water samples were concentrated either by Moore's gauze technique or by filtering through diatomaceous earth. Five enrichment media: yeast extract-Bengal rose broth (YER) with bile-oxalate-sorbose broth (BOS); 67 mmol/L phosphatebuffered saline (pH 7.6; PBS); PBS enriched with 1% mannitol and 1% peptone (PBSMP); PBS with lyzed 0.5% sheep blood (PBSB); Wauters broth (W); and five plating media: Mac Conkey agar (MC);Salmonella—Shigella agar (SS); 5% sheep blood agar (BA); lactose-sucrose-urea agar (LSU) and irgasan-novobiocin agar (IN) were used. The following strains were isolated:Y. intermedia B1 O:4,32–4,33 Lis Xz (four strains),Y. intermedia B1 O:57 Lis Xo (one strain),Y. intermedia B2 0:57 Lis Xo (one strain),Y. enterocolitica B1 O:10–34 Lis Xz (one strain), andY. frederiksenii undetermined biovar, O:16–16,29 Lis Xz (two strains). The incidence of isolation ofYersinia spp. was 7.14%. YER-BOS proved to be the best enrichment method since it allowed the highest recovering ofYersinia spp. strains. Among plating media, the best results were obtained with MC. Apparently, the isolation ofYersinia spp. can be related to environmental variables such as temperature differences between cold and warm seasons. Negative results obtained during virulence assays suggest that isolated strains lack the pathogenic potential against man.     

Extended serotyping scheme forVibrio cholerae

Fifty-seven new O serogroups have been added to the existing serotyping scheme ofVibrio cholerae to extend the scheme from O84 to O140. Prominent new additions were serogroups O139 and O140. The reference strain of O139 was isolated from a patient from an epidemic of cholera-like diarrhea in Madras, Southern India. Serogroup O140 was assigned to a group ofV. cholerae strains which were tentatively named as the Hakata serogroup and which possessed the C (Inaba) factor but not the B (Ogawa) nor the A (major specific antigen of O1 serogroup ofV. cholerae). As all antisera against reference strains ofV. cholerae contained some amount of antibody to the rough (R) antigen, all diagnostic O antisera must be absorbed with the reference rough strain, CA385.     

Characterization of rhizobia fromLeucaena

Seventy-six rhizobia were isolated from the nodules ofLeucaena plants of various genotypes growing in a wide range of soil types and climatic regions. The isolates were fast-growing and acid-producing. In establishing a serological grouping for the isolates, the intrinsic antibiotic resistance (IAR) patterns to low concentrations of eight antibiotics was helpful for selecting the strains for immunization purposes. Eight distinct somatic serogroups ofLeucaena rhizobia were identified by using strain-specific fluorescent antibodies. The results indicated that use of serological markers is a more specific technique than IAR pattern for strain identification. Strains from some different serogroups had the same IAR patterns. The immunofluorescence cross-reactions ofLeucaena rhizobia serogroups among themselves and with other species of fast- and slow-growing rhizobia were very low. Sero-grouping is ideal for use in further ecological studies in field inoculation trials.     

Analysis of insect toxin complex gene variability of <Emphasis Type="Italic">Yersinia pestis</Emphasis> and <Emphasis Type="Italic">Yersinia pseudotuberculosis</Emphasis> strains

The nucleotide sequences of the Tc’s insect toxin complex genes have been analyzed in 18 natural strains of the main and non-main subspecies of Yersinia pestis isolated in different natural foci in the Russian Federation, as well as neighboring and more remote countries, as compared to the data on Y. pestis and Y. pseudotuberculosis strains stored in the NCBI GenBank database. The nucleotide sequences of these genes in plague agent strains have been found to be highly conserved, in contrast to those of the pseudotuberculosis agent. The sequences of two genes, tcaC and tccC2, have been found to be almost identical in Y. pestis strains, whereas other three genes (tcaA, tcaB, and tccC1) contain a few mutations, which, however, are not common for all strains of the plague agent. Exceptions are only strains of the Y. pestis biovar orientalis, whose tcaB gene is in a nonfunctional state due to a nucleotide deletion. The results suggest that the formation of the species Y. pestis as an agent of a natural focal infection with a transmissive mechanism has not resulted in degradation of the Tc’s complex genes. Instead, these genes are likely to have been altered as the plague agent have been adapting to the new environment.     

Identification and characterisation of a novel adhesin Ifp in <Emphasis Type="Italic">Yersinia pseudotuberculosis</Emphasis>

Background  

In order to identify new virulence determinants in Y. pseudotuberculosis a comparison between its genome and that of Yersinia pestis was undertaken. This reveals dozens of pseudogenes in Y. pestis, which are still putatively functional in Y. pseudotuberculosis and may be important in the enteric lifestyle. One such gene, YPTB1572 in the Y. pseudotuberculosis IP32953 genome sequence, encodes a protein with similarity to invasin, a classic adhesion/invasion protein, and to intimin, the attaching and effacing protein from enteropathogenic (EPEC) and enterohaemorraghic (EHEC) Escherichia coli.     

Transmission of Yersinia pseudotuberculosis in the Pork Production Chain from Farm to Slaughterhouse

The transmission of Yersinia pseudotuberculosis in the pork production chain was followed from farm to slaughterhouse by studying the same 364 pigs from different production systems at farm and slaughterhouse levels. In all, 1,785 samples were collected, and the isolated Y. pseudotuberculosis strains were analyzed by pulsed-field gel electrophoresis. The results of microbial sampling were combined with data from an on-farm observation and questionnaire study to elucidate the associations between farm factors and the prevalence of Y. pseudotuberculosis. Following the same pigs in the production chain from farm to slaughterhouse, we were able to show similar Y. pseudotuberculosis genotypes in live animals, pluck sets (containing tongue, tonsils, esophagus, trachea, heart, lungs, diaphragm, liver, and kidneys), and carcasses and to conclude that Y. pseudotuberculosis contamination originates from the farms, is transported to slaughterhouses with pigs, and transfers to pluck sets and carcasses in the slaughter process. The study also showed that the high prevalence of Y. pseudotuberculosis in live pigs predisposes carcasses and pluck sets to contamination. When production types and capacities were compared, the prevalence of Y. pseudotuberculosis was higher in organic production than in conventional production and on conventional farms with high rather than low production capacity. We were also able to associate specific farm factors with the prevalence of Y. pseudotuberculosis by using a questionnaire and on-farm observations. On farms, contact with pest animals and the outside environment and a rise in the number of pigs on the farm appear to increase the prevalence of Y. pseudotuberculosis.     

Cytotoxicity and Calcium-Dependent Antigen of Yersinia

The relationship between invasiveness and calcium dependency was examined in various strains of Yersinia enterocolitica and Y. pseudotuberculosis by using established cell lines. Infection with calcium-dependent bacteria resulted in the formation of microvilli and the adherence of bacteria on the cell surface, and the adherent bacteria were ingested 1.5 hr after infection. Morphological changes in the cells became visible 2 to 3 hr after infection, and intracellular multiplication of the ingested bacteria was noted. When the cells were incubated with bacteria at 37 C for 1.5 hr and then at 25 C, however, the morphological changes in the infected cells were not observed. No isogenic strains that had lost calcium dependency for growth at 37 C were able to elicit the morphological changes in the cells, though they possessed the ability to adhere to and penetrate the cells. The antigen(s) supposedly related to cytotoxicity of the calcium-dependent Yersinia was sought by using antibodies prepared against calcium-dependent bacteria and then absorbed with calcium-independent bacteria and with calcium-independent bacterial cytosol. Double diffusion tests between the antisera and bacterial cytosol extracts revealed the presence of an antigen which was a cytoplasmic substance common to all calcium-dependent but not calcium-independent strains of Y. enterocolitica and Y. pseudotuberculosis.