Yersinia pestis, the cause of plague, is a recently emerged clone of Yersinia pseudotuberculosis

Plague, one of the most devastating diseases of human history, is caused by Yersinia pestis. In this study, we analyzed the population genetic structure of Y. pestis and the two other pathogenic Yersinia species, Y. pseudotuberculosis and Y. enterocolitica. Fragments of five housekeeping genes and a gene involved in the synthesis of lipopolysaccharide were sequenced from 36 strains representing the global diversity of Y. pestis and from 12-13 strains from each of the other species. No sequence diversity was found in any Y. pestis gene, and these alleles were identical or nearly identical to alleles from Y. pseudotuberculosis. Thus, Y. pestis is a clone that evolved from Y. pseudotuberculosis 1,500-20,000 years ago, shortly before the first known pandemics of human plague. Three biovars (Antiqua, Medievalis, and Orientalis) have been distinguished by microbiologists within the Y. pestis clone. These biovars form distinct branches of a phylogenetic tree based on restriction fragment length polymorphisms of the locations of the IS100 insertion element. These data are consistent with previous inferences that Antiqua caused a plague pandemic in the sixth century, Medievalis caused the Black Death and subsequent epidemics during the second pandemic wave, and Orientalis caused the current plague pandemic.

Development of digoxigenin-labeled PCR amplicon probes for use in the detection and identification of enteropathogenic Yersinia and Shiga toxin-producing Escherichia coli from foods

By including digoxigenin-11-dUTP in a polymerase chain reaction (PCR), amplification products were produced that contained nonisotopic markers for use as DNA hybridization probes. Because these labeled amplicons encode pathogenic traits for specific foodborne bacteria, they can be used to detect the presence of potentially virulent organisms that may be present in foods. This technology allows the synthesis of a variety of shelf-stable probe reagents for detecting a number of foodborne microbes of public health concern. We used this technology to detect four genes in two potential pathogens: virF and yadA in enteropathogenic Yersinia and stx1 and stx2 in Shiga-like toxin-producing Escherichia coli. Results of DNA hybridizations of dot blots of 68 Yersinia strains and 24 of 25 E. coli strains were consistent with results of equivalent PCR analyses. DNA colony hybridization with nonisotopic virF probes of colonies arising on spread plates from artificially contaminated food homogenates was able to detect potentially pathogenic Y. enterocolitica. When compared with oligonucleotide probes, amplicon probes are much less sensitive to changes in hybridization and wash temperatures, allowing greater reproducibility. Labeled probe preparations were reused more than five times and have been stored at -20 degrees C for more than 8 months. This method conveniently generates probes that are safe, stable, inexpensive, reusable, and reliable.

Comparison of systems for identification and differentiation of species within the genus Yersinia

Of four tested identification systems (API 20E, API Rapid 32 IDE, Micronaut E, and the PCR-based Yersinia enterocolitica Amplification Set), API 20E is still the system of choice for identifying pathogenic Yersinia isolates. It provides the highest sensitivity both at the genus and at the species level and has the best cost-effectiveness correlation.

Characteristics of Yersinia pseudotuberculosis isolated from animals in Brazil

Strains (105) of Yersinia pseudotuberculosis isolated in Brazil between 1982 and 1990 were bio-serotyped. They were also studied for plasmid profile, autoagglutination and calcium dependence at 37 degrees C, Congo red uptake, pyrazinamidase activity, esculin hydrolysis, salicin fermentation and drug sensitivity: 95.24% were biotype 2, serogroup O:3; 2.86% were biotype 1, serogroup O:1; and 1.90% were biotype 2, non-agglutinable. Plasmids were found in 77.14% of the strains (one in each strain). There was total correlation between the presence of the virulence plasmid and autoagglutination, calcium dependence at 37 degrees C and Congo red uptake. The esculin, salicin and pyrazinamidase tests were not efficient in differentiating pathogenic from non-pathogenic Y. pseudotuberculosis isolates. All strains were highly sensitive to the drugs used. These results indicate that Y. pseudotuberculosis is a potential pathogen for humans in Brazil, especially because the bio-serogroups detected among animals are those most frequently associated with human diseases.

Putative origin of Yersinia pseudotuberculosis in western and eastern countries. A comparison of restriction endonuclease analysis of virulence plasmids

Yersinia pseudotuberculosis isolates from Russia east of Moscow, Korea and mainland China were used for restriction endonuclease analysis of virulence plasmid (REAP) and findings were compared with REAP of isolates from Japan and Western countries. An identical REAP pattern of each serogroup 1a, 1b, 3, 4a and 4b strain was observed among isolates from Russia, Korea, mainland China, and Japan but such was absent in West European strains. Therefore, the possibility that the origin of Y. pseudotuberculosis between West Europe and eastern Eurasia east of Moscow may be from a different clone should be considered.

[The epidemiological aspects of a pseudotuberculosis polyclonal infection]

The plasmid profile of 489 Y. pseudotuberculosis strains, serovar 1b, isolated from patients during 23 outbreaks and in sporadic cases of the disease were studied. As revealed in this study, in foci with the heterogeneous population of Y. pseudotuberculosis, serovar 1b, outbreaks and sporadic cases of the disease were caused by the polyclonal population of the microorganism. The study showed that three types of outbreaks could be differentiated, depending on the clonal characteristics of the microorganism causing these outbreaks and the presence of the dominating clone of the causative agent. Y. pseudotuberculosis infection caused by the combination of several clones of the microorganism was designated as polyclonal infection.

[Yersinia pseudotuberculosis sensitivity to fluoroquinolones and the efficacy of pefloxacin in experimental pseudotuberculosis]

The sensitivity of Y. pseudotuberculosis of different origin and plasmid profile to Russian preparations of the ftoroquinolones group (cyprofloxacin, pefloxacin, norfloxacin) was studied. Of the 3 preparations under study, pefloxacin was found to be most active with respect to Y. pseudotuberculosis. The absence of relationship between antibiotic resistance in 4 Y. pseudotuberculosis strains to cyprofloxacin, pefloxacin and norfloxacin and their additional conjugative R-plasmid with molecular weights of 32 and 38 mD was noted. Pefloxacin was shown to give a good sanitation and protective effect in experimental pseudotuberculosis.

Homology with a repeated Yersinia pestis DNA sequence IS100 correlates with pesticin sensitivity in Yersinia pseudotuberculosis

We have identified IS100 sequences in a specific subset of Yersinia pseudotuberculosis isolates that were also sensitive to the Y. pestis-produced bacteriocin, pesticin. In contrast, Y. pseudotuberculosis strains which did not contain IS100 sequences were not sensitive to pesticin. We propose that IS100 serves as a molecular marker that identifies a subset of Y. pseudotuberculosis isolates that have a particularly close evolutionary and/or ecological relationship with Y. pestis.

Identification of pathogenic strains within serogroups of Yersinia pseudotuberculosis and the presence of non-pathogenic strains isolated from animals and the environment

The existence of apathogenic strains of Yersinia pseudotuberculosis (Yp) has not so far been reported. Recently, the authors characterized new serogroups and a new subgroup in Yp, that is, O9, O10, O12, O13 and O14 and O1c, and the pathogenicity of these new strains was of interest. A total of 137 strains of serogroups O1c, O6, O7, O9, O10, O11, O12, O13 and O14 of Yp were investigated for their pathogenicity in vivo and in vitro. Although catalase activity and the inv gene were detected in all strains except those of groups O13 and O14, only a few strains, from serogroups O6 and O10 caused severe infection in mice. The remaining strains caused no mortality or severe infection even when they grew in limited tissues of infected mice. All the strains of Yp not possessing the virulence plasmid p YV caused no severe infection in mice. It is evident that less pathogenic Yp exists and that not only pathogenic but also less pathogenic Yp organisms exist in the same serogroup.

Passive immunity to infection with Yersinia spp. mediated by anti-recombinant V antigen is dependent on polymorphism of V antigen

The V antigen is a 37-kDa secreted polypeptide encoded on the 70-kb virulence plasmid of pathogenic Yersinia spp. Besides having regulatory functions, it is known to be a virulence factor and a protective antigen. DNA sequencing of the most common serotypes of human pathogenic Yersinia enterocolitica and Y. pseudotuberculosis revealed that two evolutionary distinct types of V antigen exist in Yersinia spp. One type is represented by Y. enterocolitica serotype 08 strains WA, WA-314, and NCTC 10938 (designated LcrV-YenO8); the other type comprises Y. pestis, Y. pseudotuberculosis, and Y. enterocolitica serotypes O3, O9, and O5,27 (LcrV-Yps). A hypervariable region between amino acids 225 and 232 represents the main difference between the two types. By raising monospecific antisera against both types of V antigen (anti-rVO8 and anti-rVO3), we were able to demonstrate that, in general, passive immunization of mice against a challenge with yersiniae was possible with both anti-Y. enterocolitica V antigen sera. However, anti-V antigen serum was protective only if the immunizing V antigen was the same type as the V antigen produced by the infective strain. The failure of the American V antigen type represented by Y. enterocolitica serotype O8 to protect against Yersinia spp. carrying the other V antigen type (LcrV-Yps) could be an explanation for the presence of plague foci in American countries.

[Prevalence of IS285 and IS100 in Yersinia pestis and Yersinia pseudotuberculosis genomes]

Cell DNAs of various species of Enterobacteriaceae were hybridized with the probes based on IS285 and IS100, mobile genetic elements of Yersinia pestis. These IS elements are found only in the genomes of all tested Y. pestis strains and a number of strains of a related bacterium Y. pseudotuberculosis. Phylogenetic relations between the tested strains and correlation of fingerprints with the geographical origin of the strains were revealed by analysis of the hybridization profiles of Y. pestis and Y. pseudotuberculosis chromosomal DNAs with IS probes. Comparison of the chromosomal IS100 profiles of Y. pestis wild strain and its nonpigmented mutant helped us determine the minimal extension of the genetic rearrangement and detect at least three copies of the IS element in the mutant region.

Characteristics and pathogenicity of non-melibiose-fermenting strains of Yersinia pseudotuberculosis O3

The biological properties of non-melibiose-fermenting (NMF) strains of Yersinia pseudotuberculosis O3 were investigated. These strains were clearly distinguished from representative melibiose-fermenting (MF) strains of Y. pseudotuberculosis O3 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 O3 strains can probably be predicted by testing melibiose-fermentation and catalase production.

Molecular typing of Yersinia pseudotuberculosis by using an IS200-like element

The IS200-like insertion sequence (IS) is a 708-bp element recently found in Yersinia pestis. Its nucleotide sequence is 85% identical to that of IS200 recovered in most Salmonella enterica isolates. It is also present in multiple copies in Y. pseudotuberculosis. In contrast, this IS is found in some (biotype 1B strains) but not other Y. enterocolitica strains and is absent in the nonpathogenic yersiniae: Y. frederiksenii, Y. kristensenii, Y. intermedia, Y. bercovieri, and Y. mollaretii. The number and locations of the ISs in the Y. pseudotuberculosis genome vary among strains, resulting in a high degree of polymorphism, but IS fingerprints are stable after multiple subcultures of clinical isolates. The discriminative power of IS typing is better than that of ribotyping and almost as good as that of the time-consuming method of pulsotyping. Overall, IS200-like is a useful molecular marker in determining the epidemiology of Y. pseudotuberculosis infections.

Detection of Yersinia enterocolitica serogroup O:3 by a PCR method

Yersinia enterocolitica is the etiologic agent of a range of clinical situations in humans, but only a small number of serotypes are involved. Among these, Y. enterocolitica O:3 is the most frequently implicated. A PCR method was developed to detect Y. enterocolitica O:3. For this purpose, two pairs of primers were designed to amplify two fragments of the rfb cluster of Y. enterocolitica O:3: a 253-bp fragment of the rfbB gene and a 405-bp fragment of the rfbC gene. A specific detection was obtained only with rfbC primers, which yielded a PCR product of the expected size exclusively with pathogenic Y. enterocolitica of serotype O:3. This pair of primers was combined with the ail, inv, and virF primers previously described (H. Nakajima, M. Inoue, T. Mori, K.-I. Itoh, E. Arakawa, and H. Watanabe, J. Clin. Microbiol. 30:2484-2486, 1992) to allow both the detection and the differentiation between Y. pseudotuberculosis, pathogenic Y. enterocolitica of serotype O:3 and other pathogenic Y. enterocolitica.

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.

Restriction endonuclease analysis of plasmid DNA of Yersinia pseudotuberculosis infections in Shimane Prefecture, Japan

The epidemiology of Yersinia pseudotuberculosis infections in a limited area of Shimane Prefecture, Japan, was examined by serotyping and restriction endonuclease analysis of virulence plasmid DNA of Y. pseudotuberculosis strains isolated from humans, wildlife animals and river water. Almost all isolates from three sources belonged to serotype 1b REAP pattern D and serotype 4b REAP patterns B, G and L. The identity of the distribution of serotype and REAP patterns among isolates from humans, wildlife animals and river water shows that Y. pseudotuberculosis is transmitted to humans through environmental substances contaminated by wildlife animals infected with this species.

Isolation of Yersinia pseudotuberculosis from river waters in Japan and Germany using direct KOH and HeLa cell treatments

Yersinia pseudotuberculosis was recovered from precipitates directly treated with KOH and/or HeLa cell in 25.7% of 680 river water samples collected in Japan. Recovery was nil in similar samples from Germany. Treatment of precipitates by KOH and infection of HeLa cells, respectively, is an expedient and selective means for isolation of Y. pseudotuberculosis from such samples.

Studies of the biosynthesis of 3,6-dideoxyhexoses: molecular cloning and characterization of the asc (ascarylose) region from Yersinia pseudotuberculosis serogroup VA

The 3,6-dideoxyhexoses are found in the lipopolysaccharides of gram-negative bacteria, where they have been shown to be the dominant antigenic determinants. Of the five 3,6-dideoxyhexoses known to occur naturally, four have been found in various strains of Salmonella enterica (abequose, tyvelose, paratose, and colitose) and all five, including ascarylose, are present among the serotypes of Yersinia pseudotuberculosis. Although there exists one report of the cloning of the rfb region harboring the abequose biosynthetic genes from Y. pseudotuberculosis serogroup HA, the detailed genetic principles underlying a 3,6-dideoxyhexose polymorphism in Y. pseudotuberculosis have not been addressed. To extend the available information on the genes responsible for 3,6-dideoxyhexose formation in Yersinia spp. and facilitate a comparison with the established rfb (O antigen) cluster of Salmonella spp., we report the production of three overlapping clones containing the entire gene cluster required for CDP-ascarylose biosynthesis. On the basis of a detailed sequence analysis, the implications regarding 3,6-dideoxyhexose polymorphism among Salmonella and Yersinia spp. are discussed. In addition, the functional cloning of this region has allowed the expression of Ep (alpha-D-glucose cytidylyltransferase), Eod (CDP-D-glucose 4,6-dehydratase), E1 (CDP-6-deoxy-L-threo-D-glycero-4- hexulose-3-dehydrase), E3 (CDP-6-deoxy-delta 3,4-glucoseen reductase), Eep (CDP-3,6-dideoxy-D-glycero-D- glycero-4-hexulose-5-epimerase), and Ered (CDP-3,6-dideoxy-L-glycero-D-glycero-4-hexulose-4-reductase), facilitating future mechanistic studies of this intriguing biosynthetic pathway.

Pathogenicity of a strain of Yersinia pseudotuberculosis isolated from a pig with porcine colitis syndrome

A strain of Yersinia pseudotuberculosis (NCTC 12718), isolated from a seven-week-old pig suffering from an ulcerative typhlocolitis, was inoculated orally into 16 growing pigs in two separate experiments. At necropsy 10 days later, typhlocolitis was present in nine of the pigs, and it was accompanied by diarrhoea in four cases. In both the original case and in the experimental pigs, the typhlocolitis was characterised by microabscesses of the lamina propria, frequently involving ulceration or erosion of the surface epithelium. The organism was of serotype IIa, which has not been isolated previously from pigs in the United Kingdom. Y pseudotuberculosis may be the aetiological agent responsible in some cases of porcine colitis syndrome.

PCR-based random amplified polymorphic DNA fingerprinting of Yersinia pseudotuberculosis and its practical applications

The random amplified polymorphic DNA (RAPD) fingerprinting method was used to distinguish between various strains of Yersinia pseudotuberculosis, a causative agent of gastroenteritis in humans. The RAPD test uses arbitrarily chosen DNA oligomers of 10 nucleotides to prime DNA synthesis from genomic sites to which they are accidentally matched or almost matched. Most 10-nucleotide primers yielded strain-specific arrays. Ten Y. pseudotuberculosis type strains were distinguishable from each other by analyzing the RAPD arrays produced by using primers with a 50% G+C content. The RAPD patterns of Y. pseudotuberculosis strains were found to be constant regardless of the presence or absence of the large plasmid. RAPD tests were subsequently used to identify 30 clinical isolates of Y. pseudotuberculosis that were collected as the causative agent of an outbreak of Izumi fever, a disease showing clinical symptoms characteristic of atypical scarlet fever, in Japan. The RAPD arrays from all of the isolates yielded common patterns that were unique to each primer used. Since those 30 isolates belonged to serotype 5a and the restriction digest patterns of their large plasmids were all the same, the results of the RAPD tests confirmed the view that those isolates were from a single source and indicated that the RAPD test can be practically applied to survey transmission of the bacterium in humans.

Characterization of Yersinia pseudotuberculosis serogroups O9, O10 and O11; subdivision of O1 serogroup into O1a, O1b, and O1c subgroups

In this study, three new antigens (O9, O10 and O11) of Yersinia pseudotuberculosis are described. The O1 antigen is further subdivided into O1a, O1b and O1c. The methods used to prepare specific antisera for O-antigen identification are also described. Furthermore, the H antigens of these new serogroups are determined and their biochemical characteristics analysed. The antigenic formulae of the known serogroups within the basic antigenic scheme introduced by the authors' laboratories are presented.

[Large scale outbreak of Yersinia pseudotuberculosis serotype 5a infection at Noheji-machi in Aomori Prefecture]

In June 1991, there were large scale outbreaks of Yersinia pseudotuberculosis at 4 primary schools and 1 junior high-school in Noheji-machi in Aomori Prefecture. A total of 732 patients (725 pupils and school children, 7 teachers and personnel) were affected and 134 were hospitalized. Sex ratio of incidence was 1.1:1.0 without appreciable difference. Clinical symptoms (478 patients) were represented frequently by pyrexia (86.4%), eruption (73.8%), abdominal pain (66.7%), vomiting nausea (63.4%), etc., and were characterized by a strawberry tongue, pharyngeal redness, membranous desquamation of the fingers and arthralgia during convalescence. Yersinia pseudotuberculosis was isolated from 27 (81.8%) of 33 patients stool specimens, 1 waste water specimen and 2 (11.7%) of cooking employees' stool specimens. The isolates were confirmed serotype 5a, and positive for calcium-dependency and autoagglutination, and harboring 40-50 megadalton virulent plasmid. Restrictive endonuclease digestive pattern of plasmid proved to be identical. In many cases, patients' serum antibody titer showed a significant increase ratio to the isolated strain. In term of drug susceptibility, all the strains were sensitive to cefem, penicillin and amino-glycoside series and resistant to macrolide and sulfa series. The infectious source was limited to the school feeding, but the responsible food remained unknown. Mean latency and exposure day were presumed to be 6.5 days and May 30, respectively.

In vitro characteristics of Yersinia pseudotuberculosis of nonhuman primate origin

Six strains of serotypes 1 or 2 of Y. pseudotuberculosis were isolated from dead squirrel monkeys, a cotton-top tamarin and a marmoset hybrid. All strains harboured a 71.6 kb plasmid, all were totally oxacillin-resistant and partially resistant to cephalosporins. Biochemically, serotypes 1 and 2 differed from each other in their beta-galactosidase production in a nonfermenter system, whereas the lack of rhamnose, maltose, salicin and trehalose fermentation seemed to be attributable to technical causes.

Detection and identification of Yersinia pseudotuberculosis and pathogenic Yersinia enterocolitica by an improved polymerase chain reaction method

We developed a polymerase chain reaction method in order to detect and identify both Yersinia pseudotuberculosis and pathogenic Yersinia enterocolitica. Polymerase chain reaction was performed by using a mixture of primers against the inv gene from Y. pseudotuberculosis and the ail gene from pathogenic Y. enterocolitica. Further addition of primers against the plasmid-coded virF gene from Y. enterocolitica made it possible to detect a virulence-associated gene of both species at the same time. This method was proved to be an adequate and convenient procedure for routine detection and identification of these bacilli.

[The gene identification of bacterial species and serovariants by the polymerase chain reaction with universal oligonucleotides: the reidentification of earlier isolated strains of Yersinia pseudotuberculosis]

Genetic analysis of 19 standard strains belonging to 6 Yersinia species (Y. pestis, Y. pseudotuberculosis, Y. enterocolitica, Y. kirstensenii, Y. frederiksenii, Y. intermedia) revealed that gene typing by the method of polymerase chain reaction (PCR) with the use of universal primers permitted the identification of species in bacterial cultures by PCR patterns and the determination of Y. pseudotuberculosis serovars within 4 hours. By this method 23 Y. pseudotuberculosis strains (serovar 1), earlier isolated in different regions of the USSR from humans and rodents, were studied. The study showed that out of 14 strains of human origin only two strains could actually be classified with serovar 1, while the remaining strains were reidentified as belonging to serovar 5. Among 9 strains isolated from rodents those of serovar 1 prevailed (8 strains). The authors suppose that strains of serovar 5 cause outbreaks and sporadic cases of pseudotuberculosis, occurring considerably more often than it is commonly believed in the USSR.

Recognition by peptide mapping of three different structural groups of outer membrane protein YOP-1 of Yersinia enterocolitica and Yersinia pseudotuberculosis

The structural relation of YOP-1 of "european" and "american" Yersinia enterocolitica serotypes O:3, O:9, O:5,27, and O:8 and O:20, respectively, and Y. pseudotuberculosis serotypes I, II, and III was compared by sodium dodecyl sulfate polyacrylamide gel electrophoresis and peptide mapping using Staphylococcus aureus protease V8. Apparent molecular weights of YOP-1 ranged from 206,000 (O:3) to approx. 180,000 (O:8). According to their respective peptide maps YOP-1 of the "european" and "american" Y. enterocolitica serotypes and Y. pseudotuberculosis serotypes could be assigned to three different groups. Evaluation of several isolates of Y. enterocolitica serotypes O:3, O:9, and O:8 by peptide mapping indicated that YOP-1 is conserved within a serotype. However, one serotype O:8 isolate differed from the consensus peptide pattern of the other serotype O:8 and O:20 isolates. The similarity of the peptide patterns of Yersinia serotypes which predominate in certain geographical locations, i.e., "european" and "american" Y. enterocolitica serotypes, suggest common evolution of YOP-1 of these serotypes independent of the evolution of the other serotypes.

Acute mesenteric lymphadenitis due to Yersinia pseudotuberculosis lacking a virulence plasmid

A serotype 4a strain of Yersinia pseudotuberculosis lacking the virulence plasmid pYV (pYV- strain) was isolated from the mesenteric lymph nodes but not from the stool or the appendix of a 10-year-old girl with a diagnosis of acute mesenteric lymphadenitis. Microscopically, reticulocytic abscess and lymphadenitis were persent in the enlarged mesenteric lymph nodes. Antibody against the isolate was detected in the serum. The isolate was negative for the presence of plasmid pYV and plasmid pYV-mediated properties, including autoagglutination and calcium dependency, but was positive for chromosome-mediated properties, including invasion into HeLa cells and tissues of mice and the Serény test. Mice were orally infected with this pYV- strain, and rapid elimination from the intestine occurred 14 days later. Hence, the potential to inhibit the phagocytosis encoded by plasmid pYV was lacking. As the pYV- strain was recovered from the mesenteric lymph nodes and the spleen, the invasiveness was encoded by chromosomal genes. The count of the pYV- strain in the mesenteric lymph nodes increased to 10(4.6) cells per g within 4 days. These findings suggest that pYV- Y. pseudotuberculosis was the causative agent of acute mesenteric lymphadenitis in the absence of gastroenteritis.

Intestinal carriage of Yersinia pseudotuberculosis by wild birds and mammals in Japan

Fecal specimens were obtained from wild birds and mammals in the eastern part of Shimane Prefecture, Japan, an area where serotype 1b, 2b, 3, and 4b strains of Yersinia pseudotuberculosis were found to be prevalent in humans. Each of 869 animals, including 259 wild birds and 610 wild mammals, was screened for yersiniae. A total of 37 strains of Y. pseudotuberculosis were isolated from 34 (5.6%) mammals, including 23 raccoon dogs (Nyctereutes procyonoides), eight deer (Cervus nippon), two hares (Lepus brachyurus), and one marten (Martes melampus), and from two (0.8%) birds, including one eastern spot-billed duck (Anas poecilorhyncha) and one wigeon (Anas penelope). The Y. pseudotuberculosis isolates collected belonged to virulence plasmid-positive (serotypes 1b, 2b, 3, 4b, and 6) and virulence plasmid-negative (serotype 5a) strains, the most predominant serotype being 4b. The close relationship between the regional distributions of Y. pseudotuberculosis in wild animals and humans suggests that wild animals are an important source of infection.

[Microbiology and epidemiology of Yersinia infections]

Eleven species are actually recognized within the genus Yersinia of which three--Y. pestis, Y. pseudotuberculosis, and certain serovars of Y. enterocolitica--are important infectious organisms for humans and warm-blooded animals. The causative agents of yersiniosis, Y. pseudotuberculosis and Y. enterocolitica, occur world-wide in areas of moderate and subtropical climate. Asymptomatically infected warm-blooded animals, causing environmental contamination, are the most important factors for the epidemiology of yersiniosis; apathogenic Yersinia species and serovars, on the other hand, are largely adapted to environmental conditions and, with regard to their ecology, independent from warm- or cold-blooded host organisms. The agents are usually transmitted by the oral route with food-stuffs as the most important vehicle of human yersiniosis. For their isolation, enrichment procedures and selective media have been developed. The organisms are identified by biochemical reactions and can be differentiated by serological and, in case of Y. enterocolitica, also by phage-typing methods. The differentiation of pathogenic and apathogenic strains is of diagnostic importance and should be routinely performed; simple tests are available for this purpose. Demonstration of antibodies against cell-wall-associated (lipopolysaccharide) or plasmid-encoded (protein) antigens may confirm the diagnosis if the causative agents failed to be isolated.

Enteritis in sheep, goats and pigs due to Yersinia pseudotuberculosis infection

The features of naturally occurring Yersinia pseudotuberculosis serotype III infections in 16 sheep, one goat and 3 pigs, and Y. pseudotuberculosis serotype I infections in 3 goats, are described. Affected animals usually had diarrhoea and were in poor condition or emaciated. A number were moribund or dead when submitted for necropsy. Thickening of the caecal and colonic mucosa was the only gross lesion attributable to Y. pseudotuberculosis infection, with liver or other visceral abscesses not being seen. Characteristic microabscesses were demonstrated in the intestinal mucosa of 10 sheep, one goat and one pig infected with Y. pseudotuberculosis serotype III and one goat infected with Y. pseudotuberculosis serotype I. Sheep, goats and pigs dosed orally with Y. pseudotuberculosis serotype III, the serotype isolated most commonly from these species, developed intestinal infection. In sheep and pigs, infection was accompanied by diarrhoea. Haematological changes and specific antibodies were elicited in all 3 species in response to infection. Microabscesses were seen in the intestinal mucosa of all experimentally exposed animals. The occurrence of field cases and the results of experimental exposure confirm that Y. pseudotuberculosis serotype III is an enteropathogen of sheep, goats and pigs. The association of Y. pseudotuberculosis serotype I with lesions in a goat, indicates that this bacterium may also be a pathogen of this species. It is concluded that Y. pseudotuberculosis serotype III is an enteric pathogen of a wide range of ungulate species including cattle, buffalo, deer, antelopes, sheep, goats and pigs. Serotypes I and II, while having a more restricted host range, are probably also pathogens of ungulates and, in particular, deer, antelopes and goats.

[The sensitivity of Yersinia to bacteriophage Mu]

Various representatives of the genus Yersinia were found to differ in their sensitivity to the lytic action of bacteriophage Mu cts62, which could serve as an auxiliary test for the differentiation of Y. pestis and Y. pseudotuberculosis. Among the strains under study, the causative agents of plague (34 strains) were sensitive to phage Mu cts62, while the causative agents of enteric yersiniosis (42 strains) and pseudotuberculosis (73 strains), except 3 strains with the properties of Y. pestis, were resistant to this phage.

[The first case of pseudotuberculosis found in China]

This paper reports the first case of pseudotuberculosis in China. From the patient's stool, a strain of Yersinia pseudotuberculosis was isolated. The isolate has all the classical characteristics of Yersinia pseudotuberculosis and belongs to serotype IV.

Isolation and properties of carboxylesterase P4 from Yersinia pseudotuberculosis

The carboxylesterase P4 produced by Yersinia pseudotuberculosis was purified 330-fold by gel permeation and DEAE-trisacryl chromatography with a final yield of 21%. The apparent molecular weight, as determined by fast-protein liquid chromatography, was 45 kDa. The hydrolytic activity of esterase P4 was higher with the 1-naphthyl esters than with the 2-naphthyl esters of acetic, propionic and butyric acids. The apparent Km values were identical for 1-naphthyl acetate and 1-naphthyl propionate (0.15 mM). The enzyme was unstable at pH values below 5, but retained 80% of its initial activity after 30 min at 65 degrees C. It was unaffected by EDTA, eserine, tosyl-L-lysine chloromethylketone, iodoacetamide or 4-hydroxymercuribenzoate, but was strongly inhibited by low concentrations of diisopropyl fluorophosphate, suggesting the presence of serine in its active site. The purified enzyme gave a single precipitin line on Ouchterlony double immunodiffusion with homologous antiserum. This antiserum cross-reacted with the esterase bands E3 and E5 of Y. enterocolitica biotype 1, whereas there was no cross-reaction with the esterase bands produced by Y. enterocolitica biotypes 2 to 5, Y. intermedia, Y. frederiksenii, Y. kristensenii or Y. aldovae. The carboxylesterase P4 produced by Y. pestis was physicochemically, biochemically and immunologically indistinguishable from Y. pseudotuberculosis carboxylesterase P4. The latter enzyme and carboxylesterase B of Escherichia coli showed some biochemical similarities, but were antigenically unrelated. Our data confirm the relevance of esterases to phylogenetic and taxonomic studies of Enterobacteria.

Isolation of Yersinia pseudotuberculosis from water

In recent years, a number of sporadic or community infections of Yersinia pseudotuberculosis were observed in several mountain area of Okayama Prefecture, Japan. Epidemiological observations strongly suggested that drinking water in those areas, i.e. non-chlorinated water from mountain stream or wells, must be the source of the infection, so we examined the waters from the epidemic areas to detect the organisms. The examinations revealed the germs in the waters; the contamination rate of water from the northern areas is higher than that from the southern urban regions. The isolation procedures for the germs were also studied and improved. The media added with blood or hemin proved to be better for isolation of the organism.

Yersinia pseudotuberculosis infection contracted through water contaminated by a wild animal

We performed epidemiological studies on Yersinia pseudotuberculosis in one valley where a 3-year-old boy had been infected with Y. pseudotuberculosis serotype 4b in December 1982. Y. pseudotuberculosis serotype 4b was isolated from a water sample derived from a mountain stream from which the boy had drunk and from 1 of 41 rats trapped in the upper part of this stream in December 1986. The restriction endonuclease patterns of the plasmids in these isolates showed the rat and patient isolates to be identical but distinct from the water isolate. These data suggest the potential for transmission of Y. pseudotuberculosis through water contaminated by nondomesticated animals carrying this species.