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1.  Gene polymorphism analysis of Yersinia enterocolitica outer membrane protein A and putative outer membrane protein A family protein 
BMC Genomics  2014;15:201.
Background
Yersinia enterocolitica outer membrane protein A (OmpA) is one of the major outer membrane proteins with high immunogenicity. We performed the polymorphism analysis for the outer membrane protein A and putative outer membrane protein A (p-ompA) family protein gene of 318 Y. enterocolitica strains.
Results
The data showed all the pathogenic strains and biotype 1A strains harboring ystB gene carried both ompA and p-ompA genes; parts of the biotype 1A strains not harboring ystB gene carried either ompA or p-ompA gene. In non-pathogenic strains (biotype 1A), distribution of the two genes and ystB were highly correlated, showing genetic polymorphism. The pathogenic and non-pathogenic, highly and weakly pathogenic strains were divided into different groups based on sequence analysis of two genes. Although the variations of the sequences, the translated proteins and predicted secondary or tertiary structures of OmpA and P-OmpA were similar.
Conclusions
OmpA and p-ompA gene were highly conserved for pathogenic Y. enterocolitica. The distributions of two genes were correlated with ystB for biotype 1A strains. The polymorphism analysis results of the two genes probably due to different bio-serotypes of the strains, and reflected the dissemination of different bio-serotype clones of Y. enterocolitica.
doi:10.1186/1471-2164-15-201
PMCID: PMC3995578  PMID: 24628971
Yersinia enterocolitica; ompA; p-ompA; ystB
2.  Identification of Virulence-Associated Characteristics in Clinical Isolates of Yersinia enterocolitica Lacking Classical Virulence Markers 
Infection and Immunity  1998;66(3):1113-1120.
Yersinia enterocolitica is an important enteric pathogen which has well-defined virulence determinants that allow the bacteria to become established in their hosts and overcome host defenses. A number of strains obtained from patients with diarrhea, however, lack these genes. Accordingly, the mechanisms by which they cause disease are uncertain. Most of these isolates belong to biotype 1A. Strains of this biotype are also frequently isolated from a variety of nonclinical sources, such as food, soil, water, and healthy animals, and there is evidence that some of these strains are avirulent. In this study we investigated 111 strains of Y. enterocolitica biotype 1A, 79 from symptomatic humans and 32 from nonclinical sources, for virulence-associated characteristics. DNA hybridization studies showed that none of the strains carried sequences homologous with pYV, the ∼70-kb Yersinia virulence plasmid. Some strains hybridized with DNA probes for one of the following chromosomal virulence-associated genes: ail (7.2%), myfA (11.7%), ystA (0.9%), and ystB (85%). In addition, 33 strains (29.7%) produced an enterotoxin that was reactive in infant mice. However, the frequencies of these virulence-associated properties in clinical and nonclinical isolates were similar. Clinical isolates invaded HEp-2 cells and Chinese hamster ovary cells to a significantly greater extent than nonclinical strains (P ≤ 0.002). In addition, clinical strains colonized the intestinal tracts of perorally inoculated mice for significantly longer periods than nonclinical isolates (P ≤ 0.01). Light and electron microscopic examination of tissue culture cells incubated with invasive yersiniae revealed that the bacteria invaded selected cells in large numbers but spared others, suggesting that biotype-1A strains of Y. enterocolitica may invade cells by a novel mechanism. These results indicate that some clinical isolates of Y. enterocolitica which lack classical virulence markers may be able to cause disease via virulence mechanisms which differ from those previously characterized in enteropathogenic Yersinia species.
PMCID: PMC108023  PMID: 9488403
3.  PCR Detection of Virulence Genes in Yersinia enterocolitica and Yersinia pseudotuberculosis and Investigation of Virulence Gene Distribution 
PCR-based assays were developed for the detection of plasmid- and chromosome-borne virulence genes in Yersinia enterocolitica and Yersinia pseudotuberculosis, to investigate the distribution of these genes in isolates from various sources. The results of PCR genotyping, based on 5 virulence-associated genes of 140 strains of Y. enterocolitica, were compared to phenotypic tests, such as biotyping and serotyping, and to virulence plasmid-associated properties such as calcium-dependent growth at 37°C and Congo red uptake. The specificity of the PCR results was validated by hybridization. Genotyping data correlated well with biotype data, and most biotypes resulted in (nearly) homogeneous genotypes for the chromosomal virulence genes (ystA, ystB, and ail); however, plasmid-borne genes (yadA and virF) were detected with variable efficiency, due to heterogeneity within the bacterial population for the presence of the virulence plasmid. Of the virulence genes, only ystB was present in biotype 1A; however, within this biotype, pathogenic and apathogenic isolates could not be distinguished based on the detection of virulence genes. Forty Y. pseudotuberculosis isolates were tested by PCR for the presence of inv, yadA, and lcrF. All isolates were inv positive, and 88% of the isolates contained the virulence plasmid genes yadA and lcrF. In conclusion, this study shows that genotyping of Yersinia spp., based on both chromosome- and plasmid-borne virulence genes, is feasible and informative and can provide a rapid and reliable genotypic characterization of field isolates.
doi:10.1128/AEM.69.3.1810-1816.2003
PMCID: PMC150046  PMID: 12620874
4.  Characterization of Yersinia enterocolitica Biotype 1A Strains Isolated from Swine Slaughterhouses and Markets 
The Scientific World Journal  2013;2013:769097.
Yersinia enterocolitica is an important foodborne pathogen that causes illness in humans and animals. Y. enterocolitica is also the most heterogeneous species of the genus and is divided into distinct serotypes and over six biotypes. Y. enterocolitica biotype 1A strains are classically considered as nonpathogenic; however, some biotype 1A isolates have been considered as causative of gastrointestinal disease, yielding symptoms indistinguishable from those produced by pathogenic biotypes. Even after decades of isolation of clinical strains, the pathogenic mechanisms of these isolates are still not fully understood. In the present study, 122 Yersinia enterocolitica biotype 1A strains isolated from swine slaughterhouses and meat markets in Sao Paulo, Brazil, were characterized according to the presence of the virulence genes ail, virF, and ystA. A total of 94 strains were positive to at least one virulence gene (77.05%), and 67 were positive to all of them (54.92%). Twenty-two strains were submitted to PFGE genotyping resulting in 22 distinct pulsotypes, varying from 50% to 84% of genetic similarity. Any clustering tendency among pulsotypes related to origin, isolation site, or even virulence profile was not observed. The present study reports an important contamination of the environment in swine slaughterhouses, meat markets, and pork, by potentially virulent Y. enterocolitica biotype 1A.
doi:10.1155/2013/769097
PMCID: PMC3588180  PMID: 23476146
5.  The use of the HRM method for identifying possible mutations in the ymoA gene region and evaluating their influence on the enterotoxic properties of Y. enterocolitica strains 
BMC Veterinary Research  2014;10(1):207.
Background
The yst gene that encodes the production of Yst enterotoxins is one of the most important and reliable virulence markers. Its ability to produce Yst has been demonstrated in pathogenic strains isolated from clinical cases of yersiniosis with diarrhea. However, not all yst positive strains produce enterotoxins. According to some authors, Yst production can be restored in a silent strain by ymoA mutation. In this study, the HRM method was applied to identify ymoA single nucleotide polymorphism with the aim of evaluating their influence on the enterotoxic properties of Y. enterocolitica strains.
Results
Two genotypes (A and G) of the examined nucleotide sequence and some variations were detected in the HRM analysis. A phylogenetic analysis of 10 genotype A nucleotide sequences revealed 100% similarity with the Yersinia enterocolitica subsp. enterocolitica 8081 genome NCBI Acc. No. AM286415. An analysis of 10 genotype G nucleotide sequences and 3 variations sequences revealed two point mutations in the examined region: transition A3387326G and insertion A in position 3387368. However, no mutations were observed in the coding region of any of the examined ymoA gene fragments. Genotype G was identified in nearly all Y. enterocolitica strains isolated from pigs. Only 4 nucleotide sequences were similar to AM286415 and did not feature point mutations. In case of human Y. enterocolitica strains 31 were classified as belonging to genotype A, the remaining 59 belonged to genotype G and were characterized by the presence of point mutations.
Conclusions
No correlations were observed between enterotoxic properties and the presence of mutations in the ymoA gene region of Y. enterocolitica strains isolated from both humans and pigs.
doi:10.1186/s12917-014-0207-6
PMCID: PMC4177235  PMID: 25234736
Yersinia enterocolitica; ymoA gene; Yst enterotoxins; HRM; SNP
6.  Genotypic Characterization of Yersinia enterocolitica Biotype 4/O:3 Isolates from Pigs and Slaughterhouses Using SE-AFLP, ERIC-PCR, and PFGE 
Journal of Pathogens  2013;2013:521510.
Yersinia enterocolitica is a foodborne pathogen that causes illness in humans and animals. The biotype 4/O:3 has been commonly associated with yersiniosis and is characterized by the presence of chromosomal and extra-chromosomal virulence genes. Molecular typing methods have been successfully used to characterize Y. enterocolitica genetic heterogeneity and to study the epidemiology of the bacteria from different origins. In this study, 320 Y. enterocolitica biotype 4/O:3 isolates originating in pigs and slaughterhouses were characterized according to the virulence profile, and 61 isolates were typified through SE-AFLP, ERIC-PCR, and PFGE techniques. The majority of the isolates originated from pigs, and the predominant virulence profile was ail+ virF+ rfbC+ ystA+, representing 83.4% of the tested isolates. All of the Y. enterocolitica 4/O:3 isolates were positive for at least ystA gene. The SE-AFLP and ERIC-PCR patterns were highly homogeneous. The SE-AFLP was more discriminative than the ERIC-PCR and tended to cluster isolates according to the slaughterhouse. Despite the limited genetic diversity of Y. enterocolitica 4/O:3, PFGE was shown to be the most discriminative technique considering one band of difference. Fattening pigs proved to be an important reservoir of Y. enterocolitica biotype 4/O:3 carrying virulence genes.
doi:10.1155/2013/521510
PMCID: PMC3683492  PMID: 23819054
7.  Detection of pathogenic Yersinia enterocolitica by polymerase chain reaction and digoxigenin-labeled polynucleotide probes. 
Journal of Clinical Microbiology  1992;30(10):2668-2673.
Yersinia enterocolitica is widespread in nature, but only a few bioserotypes are involved in human infections. Pigs are considered to be the major reservoirs of pathogenic strains. It is essential to have an accurate and rapid method for the detection of pathogenic yersiniae. To achieve this objective, 19-base synthetic oligonucleotide primers were used in a polymerase chain reaction (PCR) to detect the ail gene (which is conserved only in pathogenic strains) in strains of Y. enterocolitica and related species originating from pigs or pork products. Digoxigenin-labeled probes derived from the ail, inv, and yst genes were also evaluated on these strains. The PCR amplified a 273-bp fragment of the ail gene involved in eukaryotic cell invasion and serum resistance. The PCR detected template DNA only in strains of Y. enterocolitica traditionally classified as human pathogens but not in biotype 1A strains and related species. Other members of the family Enterobacteriaceae were also negative for the target gene. The digoxigenin-labeled ail probe gave identical results to the PCR. By use of this nonisotopic method, inv-homologous DNA was detected only among yersiniae, except for Y. ruckeri. Although all pathogenic serotypes of Y. enterocolitica were positive for the heat-stable enterotoxin yst gene, two strains of biotype 1A, one Y. intermedia strain, and six other species of the Enterobacteriaceae were also positive. Our results support the notion that pigs constitute an important reservoir of pathogenic Y. enterocolitica and that the inv-homologous sequence is Yersinia specific.
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PMCID: PMC270496  PMID: 1400967
8.  Development of a highly specific assay for rapid identification of pathogenic strains of Yersinia enterocolitica based on PCR amplification of the Yersinia heat-stable enterotoxin gene (yst). 
Journal of Clinical Microbiology  1997;35(6):1636-1638.
The chromosomal gene yst, which encodes a heat-stable enterotoxin of Yersinia enterocolitica, is a useful diagnostic marker because it occurs only in invasive strains of this species. A homologous gene also occurs in some strains of Yersinia kristensenii. Sequence analysis of the yst genes from two different strains of Y. enterocolitica and from Y. kristensenii revealed a substantial number of mismatches at the 3' ends of the yst genes of the so-called American and European biotypes of Y. enterocolitica. Moreover, several mismatches and a deletion of 5 codons were found in the yst of Y. kristensenii. These findings were used to develop a PCR-based assay for yst of Y. enterocolitica which yielded a detectable product in as little as 50 min. The assay was 100% specific in terms of its ability to identify potentially pathogenic strains of Y. enterocolitica regardless of biotype or serotype. The PCR yielded an amplicon that was visible on agarose gel electrophoresis from as few as 100 CFU, or 10 CFU when the PCR was combined with dot blot hybridization with a digoxigenin-labeled oligonucleotide probe that corresponded to an internal sequence of yst. These results establish the value of the yst gene as a target for the identification of pathogenic bioserotypes of Y. enterocolitica and the usefulness of PCR for this purpose.
PMCID: PMC229810  PMID: 9163505
9.  Role of Yersinia enterocolitica Yst toxin in experimental infection of young rabbits. 
Infection and Immunity  1992;60(10):4269-4277.
We constructed a Yst-negative mutant of Yersinia enterocolitica W1024 by reverse genetics, and we compared the virulence of the yst+ and yst isogenic strains in an experimental oral infection of the young rabbit. The rabbits infected with the yst+ strain suffered from the diarrhea and lost weight, and most of them died. By contrast, the occurrence of diarrhea, weight loss, and death in the group of rabbits infected with the yst mutant was as low as that in the group of uninfected rabbits. Bacteria from both strains were excreted in the feces and induced a serum antibody response against Yop proteins. The yst mutant disappeared more rapidly from the feces. We conclude that the enterotoxin Yst is a major factor involved in the Y. enterocolitica-associated diarrhea in the young rabbit. Given the similarity with the symptoms observed for children, this result suggests that Yst could also be an important factor in diarrhea in young children infected with Y. enterocolitica.
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PMCID: PMC257462  PMID: 1398938
10.  Molecular epidemiology of Yersinia enterocolitica O:3 infections: use of chromosomal DNA restriction fragment length polymorphisms of rRNA genes. 
Journal of Clinical Microbiology  1991;29(11):2368-2374.
Yersinia enterocolitica is a major enteric pathogen associated with a wide variety of clinical and immunologic manifestations, including transfusion-associated disease, from which there is a high mortality. Although previously rare in the United States, in the late 1980s Y. enterocolitica O:3 emerged as the predominant serotype in the United States, as it has been in Canada, Europe, and Japan. Epidemiologic investigation of this serogroup has been hampered by the limited availability of a phage typing system and the fact that Y. enterocolitica harbors few plasmids that are useful as strain markers. We therefore analyzed whole-cell DNA restriction fragment length polymorphisms of rRNA genes (ribotyping) to study a group of 61 (50 human, 11 porcine) Y. enterocolitica isolates. Initially, 20 different restriction enzymes were used: NciI appeared to give the best discrimination of hybridization banding patterns (ribotypes) within Y. enterocolitica O:3. Ribotyping distinguished seven clones among all the study isolates and four clones within Y. enterocolitica O:3 (53 isolates studied) and clearly differentiated Y. enterocolitica O:3 from Y. enterocolitica O:9; O:1,2,3; O:20; and O:5,27. Most serogroup O:3 isolates belonged to two clones, ribotypes I and II, including 23 of 24 Y. enterocolitica O:3 (13 human, 11 porcine chitterling) isolates recovered from a recent outbreak of Y. enterocolitica in children in Atlanta associated with chitterling preparation and 3 transfusion-associated O:3 isolates from the United States. Y. enterocolitica O:3 ribotypes I and II were also isolated in Japan, ribotypes II and IV were isolated in Belgium, and ribotype I was isolated in Canada. Ribotype patterns I and II corresponded to phage types 9b and 8, respectively. Ribotyping was able to distinguish individual strains of Y. enterocolitica O:3, but suggests that a limited number of clones have disseminated within the United States and globally. The finding of identical ribotype patterns in chitterling and human specimens from the Atlanta outbreak supports epidemiologic evidence that swine were the source of infection and major reservoir for Y. enterocolitica O:3.
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PMCID: PMC270340  PMID: 1723068
11.  Application of Comparative Phylogenomics To Study the Evolution of Yersinia enterocolitica and To Identify Genetic Differences Relating to Pathogenicity 
Journal of Bacteriology  2006;188(10):3645-3653.
Yersinia enterocolitica, an important cause of human gastroenteritis generally caused by the consumption of livestock, has traditionally been categorized into three groups with respect to pathogenicity, i.e., nonpathogenic (biotype 1A), low pathogenicity (biotypes 2 to 5), and highly pathogenic (biotype 1B). However, genetic differences that explain variation in pathogenesis and whether different biotypes are associated with specific nonhuman hosts are largely unknown. In this study, we applied comparative phylogenomics (whole-genome comparisons of microbes with DNA microarrays combined with Bayesian phylogenies) to investigate a diverse collection of 94 strains of Y. enterocolitica consisting of 35 human, 35 pig, 15 sheep, and 9 cattle isolates from nonpathogenic, low-pathogenicity, and highly pathogenic biotypes. Analysis confirmed three distinct statistically supported clusters composed of a nonpathogenic clade, a low-pathogenicity clade, and a highly pathogenic clade. Genetic differences revealed 125 predicted coding sequences (CDSs) present in all highly pathogenic strains but absent from the other clades. These included several previously uncharacterized CDSs that may encode novel virulence determinants including a hemolysin, a metalloprotease, and a type III secretion effector protein. Additionally, 27 CDSs were identified which were present in all 47 low-pathogenicity strains and Y. enterocolitica 8081 but absent from all nonpathogenic 1A isolates. Analysis of the core gene set for Y. enterocolitica revealed that 20.8% of the genes were shared by all of the strains, confirming this species as highly heterogeneous, adding to the case for the existence of three subspecies of Y. enterocolitica. Further analysis revealed that Y. enterocolitica does not cluster according to source (host).
doi:10.1128/JB.188.10.3645-3653.2006
PMCID: PMC1482848  PMID: 16672618
12.  Nucleotide sequence of yst, the Yersinia enterocolitica gene encoding the heat-stable enterotoxin, and prevalence of the gene among pathogenic and nonpathogenic yersiniae. 
Infection and Immunity  1990;58(9):2983-2988.
The gene encoding the heat-stable enterotoxin (yst) was cloned from the chromosome of Yersinia enterocolitica W1024 (serotype O:9), and the nucleotide sequence was determined. The yst gene encodes a 71-amino-acid polypeptide. The C-terminal 30 amino acids of the predicted protein exactly correspond to the amino acid sequence of the toxin extracted from culture supernatants (T. Takao, N. Tominaga, and Y. Shimonishi, Biochem. Biophys. Res. Commun. 125:845-851, 1984). The N-terminal 18 amino acids have the properties of a signal sequence. The central 22 residues are removed during or after the secretion process. This organization in three domains (Pre, Pro, and mature Yst) resembles that of the enterotoxin STa of Escherichia coli. The degree of conservation between the E. coli and Y. enterocolitica toxins is much lower in the Pre and the Pro domains than in the mature proteins. The mature toxin of Y. enterocolitica is much larger than that of E. coli, but the active domain appears to be highly conserved. The yst gene of Y. enterocolitica introduced in E. coli K-12 directed the secretion of an active toxin. The cloned yst gene was used as an epidemiological probe among a collection of 174 strains representative of all Yersinia species except Yersinia pestis and numerous Y. enterocolitica subgroups. In Y. enterocolitica, there was a clear-cut difference between pathogenic and nonpathogenic strains: 89 of 89 pathogenic and none of 51 nonpathogenic strains contained yst-homologous DNA, suggesting that Yst is involved in pathogenesis. Among the other Yersinia species, only four strains of Yersinia kristensenii had DNA homologous to yst.
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PMCID: PMC313599  PMID: 2201642
13.  Homologues of Insecticidal Toxin Complex Genes in Yersinia enterocolitica Biotype 1A and Their Contribution to Virulence  
Infection and Immunity  2005;73(10):6860-6867.
Yersinia enterocolitica is an enteric pathogen that consists of six biotypes: 1A, 1B, 2, 3, 4, and 5. Strains of the latter five biotypes can carry a virulence plasmid, known as pYV, and several well-characterized chromosomally encoded virulence determinants. Y. enterocolitica strains of biotype 1A lack the virulence-associated markers of pYV-bearing strains and were once considered to be avirulent. There is growing epidemiological, clinical, and experimental evidence, however, to suggest that some biotype 1A strains are virulent and can cause gastrointestinal disease. To identify potential virulence genes of pathogenic strains of Y. enterocolitica biotype 1A, we used genomic subtractive hybridization to determine genetic differences between two biotype 1A strains: an environmental isolate, Y. enterocolitica IP2222, and a clinical isolate, Y. enterocolitica T83. Among the Y. enterocolitica T83-specific genes we identified were three, tcbA, tcaC, and tccC, that showed homology to the insecticidal toxin complex (TC) genes first discovered in Photorhabdus luminescens. The Y. enterocolitica T83 TC gene homologues were expressed by Y. enterocolitica T83 and were significantly more prevalent among clinical biotype 1A strains than other Yersinia isolates. Inactivation of the TC genes in Y. enterocolitica T83 resulted in mutants which were attenuated in the ability to colonize the gastrointestinal tracts of perorally infected mice. These results indicate that products of the TC gene complex contribute to the virulence of some strains of Y. enterocolitica biotype 1A, possibly by facilitating their persistence in vivo.
doi:10.1128/IAI.73.10.6860-6867.2005
PMCID: PMC1230942  PMID: 16177365
14.  Yersinia enterocolitica in sheep - a high frequency of biotype 1A 
Background
Pigs are regarded as the main reservoir for human pathogenic Yersinia enterocolitica, which is dominated by bioserotype 4/O:3. Other animals, including sheep, have occasionally been reported as carriers of pathogenic strains of Y. enterocolitica. To our knowledge, this is the first study performed in the Nordic countries in which the presence of Y. enterocolitica in sheep is investigated.
Methods
Tonsils and faecal samples collected from sheep slaughtered on the island Gotland (Sweden) from September 2010 through January 2011 were analysed for presence of Y. enterocolitica. In an attempt to maximize recovery, several cultural strategies were applied. Various non-selective media were used and different temperatures and durations of the enrichment were applied before subculturing on Cefsulodin Irgasan Novobiocin (CIN) agar. Presumptive Y. enterocolitica colonies were subjected to urease, API 20E and agglutination test. Yersinia enterocolitica isolates were biotyped, serotyped, and tested for pathogenicity using a TaqMan PCR directed towards the ail-gene that is associated with human pathogenic strains of Y. enterocolitica.
Results
The samples collected from 99 sheep yielded 567 presumptive Y. enterocolitica colonies. Eighty urease positive isolates, from 35 sheep, were identified as Y. enterocolitica by API 20E. Thirty-four of 35 further subtyped Y. enterocolitica isolates, all from faecal samples, belonged to biotype 1A serotype O:5, O:6. O:13,7 and O:10. One strain was Yersinia mollaretii serotype O:62. No human pathogenic strains of Y. enterocolitica were found in the investigated sheep. Other species identified were Y. kristensenii (n = 4), Y. frederiksenii/intermedia (n = 3), Providencia rettgeri (n = 2), Serratia marcescens (n = 1) and Raoultella ornithinolytica (n = 1).
Conclusions
This study does not support the hypothesis that sheep play an important role in transmission of the known human pathogenic Y. enterocolitica in the studied geographical region. However, because there are studies indicating that some strains of Y. enterocolitica biotype 1A may cause disease in humans, the relative importance of sheep as carriers of human pathogenic strains of Y. enterocolitica remains unclear. Tonsils do not appear to be favourable sites for Y. enterocolitica biotype 1A in sheep.
doi:10.1186/1751-0147-54-39
PMCID: PMC3432015  PMID: 22748116
Yersinia enterocolitica; Sheep; Biotype 1A; Zoonosis; Tonsil; Faeces
15.  Tracing genomic variations in two highly virulent Yersinia enterocolitica strains with unequal ability to compete for host colonization 
BMC Genomics  2012;13:467.
Background
Yersinia enterocolitica is a gastrointestinal foodborne pathogen found worldwide and which especially affects infants and young children. While different bioserotypes have been associated with varying pathogenicity, research on Y. enterocolitica is mainly conducted on the highly virulent mouse-lethal strains of biotype 1B and serotype O:8. We demonstrate here that two Y. enterocolitica bioserotype 1B/O:8 strains, 8081 and WA-314, display different virulence and fitness properties in a mouse model. In vivo co-infection experiments revealed that strain WA-314 overcomes strain 8081 in the colonization of spleen and liver. To trace the reasons of this incongruity, we present here the first high-quality sequence of the whole genome of strain WA-314 and compare it to the published genome of strain 8081.
Results
Regions previously accepted as unique to strain 8081, like the YAPI and YGI-3 genomic islands, are absent from strain WA-314, confirming their strain-specificity. On the other hand, some fitness- and bacterial competition-associated features, such as a putative colicin cluster and a xenobiotic-acyltransferase-encoding gene, are unique to strain WA-314. Additional acquisitions of strain WA-314 are seven prophage-like regions. One of these prophages, the 28-kb P4-like prophage YWA-4, encodes a PilV-like protein that may be used for adhesion to and invasion of the intestinal cells. Furthermore, a putative autotransporter and two type 1 fimbrial proteins of strain WA-314 show a sequence similarity <50% with the orthologous proteins in strain 8081. The dissimilar sequences of these proteins indicate possible different functions or interaction modes, reflecting the specific adhesion properties of Y. enterocolitica strains 8081 and WA-314 and thus the different efficiency of host colonization. Further important differences were found in two pYV plasmid-encoded virulence factors, YopM and YscP. The impact of these differences on virulence is discussed.
Conclusions
Our study emphasizes that the virulence of pathogens can be increased, by acquiring new genes and/or improving the function of essential virulence proteins, resulting in permanently hyper-virulent strains. This work also highlights the importance of addressing genetic and phenotypic variations among closely related bacterial strains, even those belonging to the same bioserotype.
doi:10.1186/1471-2164-13-467
PMCID: PMC3469391  PMID: 22963272
Yersinia enterocolitica; Hyper-virulent; Genome comparison; Diversity; Host colonization; Virulence factors; YscP; YopM
16.  Identification of Yersinia enterocolitica at the Species and Subspecies Levels by Fourier Transform Infrared Spectroscopy ▿  
Applied and Environmental Microbiology  2009;75(18):5809-5813.
Yersinia enterocolitica and other Yersinia species, such as Y. pseudotuberculosis, Y. bercovieri, and Y. intermedia, were differentiated using Fourier transform infrared spectroscopy (FT-IR) combined with artificial neural network analysis. A set of well defined Yersinia strains from Switzerland and Germany was used to create a method for FT-IR-based differentiation of Yersinia isolates at the species level. The isolates of Y. enterocolitica were also differentiated by FT-IR into the main biotypes (biotypes 1A, 2, and 4) and serotypes (serotypes O:3, O:5, O:9, and “non-O:3, O:5, and O:9”). For external validation of the constructed methods, independently obtained isolates of different Yersinia species were used. A total of 79.9% of Y. enterocolitica sensu stricto isolates were identified correctly at the species level. The FT-IR analysis allowed the separation of all Y. bercovieri, Y. intermedia, and Y. rohdei strains from Y. enterocolitica, which could not be differentiated by the API 20E test system. The probability for correct biotype identification of Y. enterocolitica isolates was 98.3% (41 externally validated strains). For correct serotype identification, the probability was 92.5% (42 externally validated strains). In addition, the presence or absence of the ail gene, one of the main pathogenicity markers, was demonstrated using FT-IR. The probability for correct identification of isolates concerning the ail gene was 98.5% (51 externally validated strains). This indicates that it is possible to obtain information about genus, species, and in the case of Y. enterocolitica also subspecies type with a single measurement. Furthermore, this is the first example of the identification of specific pathogenicity using FT-IR.
doi:10.1128/AEM.00206-09
PMCID: PMC2747871  PMID: 19617388
17.  Homology Analysis of Pathogenic Yersinia Species Yersinia enterocolitica, Yersinia pseudotuberculosis, and Yersinia pestis Based on Multilocus Sequence Typing 
We developed a multilocus sequence typing (MLST) scheme and used it to study the population structure and evolutionary relationships of three pathogenic Yersinia species. MLST of these three Yersinia species showed a complex of two clusters, one composed of Yersinia pseudotuberculosis and Yersinia pestis and the other composed of Yersinia enterocolitica. Within the first cluster, the predominant Y. pestis sequence type 90 (ST90) was linked to Y. pseudotuberculosis ST43 by one locus difference, and 81.25% of the ST43 strains were from serotype O:1b, supporting the hypothesis that Y. pestis descended from the O:1b serotype of Y. pseudotuberculosis. We also found that the worldwide-prevalent serotypes O:1a, O:1b, and O:3 were predominated by specific STs. The second cluster consisted of pathogenic and nonpathogenic Y. enterocolitica strains, two of which may not have identical STs. The pathogenic Y. enterocolitica strains formed a relatively conserved group; most strains clustered within ST186 and ST187. Serotypes O:3, O:8, and O:9 were separated into three distinct blocks. Nonpathogenic Y. enterocolitica STs were more heterogeneous, reflecting genetic diversity through evolution. By providing a better and effective MLST procedure for use with the Yersinia community, valuable information and insights into the genetic evolutionary differences of these pathogens were obtained.
doi:10.1128/JCM.02185-13
PMCID: PMC3911470  PMID: 24131695
18.  Genotypic Diversity and Virulence Characteristics of Clinical and Environmental Vibrio vulnificus Isolates from the Baltic Sea Region 
Applied and Environmental Microbiology  2013;79(12):3570-3581.
The genetic diversity of Vibrio vulnificus isolates from clinical and environmental sources originating from the Baltic Sea region was evaluated by multilocus sequence typing (MLST), and possible relationships between MLST clusters, potential genotypic and phenotypic traits associated with pathogenicity, and source of isolation were investigated. The studied traits included genotyping of polymorphic loci (16S rRNA, vcg, and pilF), presence/absence of potential virulence genes, including nanA, nab, and genes of pathogenicity regions, metabolic features, hemolytic activity, resistance to human serum, and cytotoxicity to human intestinal cells. MLST generated 35 (27 new) sequence types and divided the 53 isolates (including four reference strains) into two main clusters, with cluster I containing biotype 1 and 2 isolates of mainly environmental origin and cluster II containing biotype 1 isolates of mainly clinical origin. Cluster II isolates were further subdivided into two branches. Branch IIB included isolates from recent cases of wound infections that were acquired at the German Baltic Sea coastline between 2010 and 2011 and isolates from seawater samples of the same regions isolated between 1994 and 2010. Comparing the MLST data with the results of genotyping and phenotyping showed that strains of MLST cluster II possess a number of additional pathogenicity-associated traits compared to cluster I strains. Rapid microbiological methods such as matrix-assisted laser desorption ionization–time of flight (MALDI-TOF) mass spectrometry combined with typing of selected virulence-associated traits (e.g., serum resistance, mannitol fermentation, nanA, and pathogenicity region XII) could be used for risk assessment purposes regarding V. vulnificus strains isolated from the Baltic Sea region.
doi:10.1128/AEM.00477-13
PMCID: PMC3675912  PMID: 23542621
19.  Nutritional requirements for synthesis of heat-stable enterotoxin by Yersinia enterocolitica. 
Applied and Environmental Microbiology  1993;59(10):3314-3320.
A defined medium that supported the growth of and synthesis of heat-stable enterotoxin (YST) by clinical isolates of Yersinia enterocolitica at levels equivalent to those observed in a complex Trypticase soy broth-0.6% yeast extract medium was developed. The defined medium contained four amino acids (L-methionine, L-glutamic acid, glycine, and L-histidine), inorganic salts, N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES) buffer, and potassium gluconate as the carbon source. Methionine was required for growth by most strains of Y. enterocolitica used in this study; thus, it was not possible to determine whether it was also required for the synthesis of YST. The other 17 amino acids commonly found in proteins did not stimulate the synthesis of YST when added to the defined medium. The yield of YST observed with other carbon sources fermented by Y. enterocolitica ranged from 4- to 26-fold lower than that obtained with potassium gluconate. The divalent cations Ca2+ and Mn2+ had no effect on the synthesis of YST; however, concentrations of Fe2+ above 10 microM inhibited the synthesis of the enterotoxin. The addition of a mixture of pyrimidines containing thymine, cytosine, and uracil, each at a concentration of 2.0 mM, stimulated the synthesis of YST by 10 to 15%, whereas a mixture of adenine and guanine, each at a similar concentration, inhibited the synthesis of YST. Vitamins had no effect on the amounts of YST produced by Y. enterocolitica strains grown in the defined medium.(ABSTRACT TRUNCATED AT 250 WORDS)
PMCID: PMC182453  PMID: 8250556
20.  Assessment of enterotoxin production by Yersinia enterocolitica and identification of a novel heat-stable enterotoxin produced by a noninvasive Y. enterocolitica strain isolated from clinical material. 
Infection and Immunity  1993;61(2):764-767.
Twenty-eight clinical isolates of Yersinia enterocolitica were investigated for their abilities to produce heat-stable enterotoxin (YST). All 21 invasive strains (serogroup O3 biotype 4) carried the previously described gene for YST (yst), with toxin detectable in culture supernatants from 20 strains. One of seven noninvasive, biotype 1A strains also had enterotoxic activity, despite failure to hybridize with a probe for yst. The toxin produced by this noninvasive (serogroup O6) strain resembled YST in terms of molecular size, heat stability, and solubility in methanol. It differed from YST, however, with respect to regulation of its production by temperature and its mechanism of action, which did not appear to involve cyclic GMP.
PMCID: PMC302791  PMID: 8380799
21.  Virulence and phenotypic characterization of Yersinia enterocolitica isolated from humans in the United States. 
Journal of Clinical Microbiology  1983;17(1):128-138.
Yersinia enterocolitica was recently reclassified into Yersinia enterocolitica sensu stricto and three additional species. With this new classification, it was of interest to reexamine pathogenicity previously ascribed to Y. enterocolitica. All available clinical isolates of Y. enterocolitica sent to the Centers for Disease Control from 1970 through 1980 were selected for characterization and comparison. One-hundred such strains had been submitted, from 21 states. Most (85%) were biotype 1, and O:8 was the most common of the 24 serotypes encountered. All strains were examined by several virulence assays. Two strains caused conjunctivitis in guinea pigs, 7 were lethal for mice, 54 invaded HEp2 cells, 18 produced a heat-stable enterotoxin, 9 were calcium dependent, 20 autoagglutinated, and 34 had a distinctive colonial morphology at 37 degrees C. Ten isolates of each of the new species that had previously been grouped with Y. enterocolitica (Y. kristensenii, Y. intermedia, and Y. frederiksenii) were characterized and were generally negative in all assays. This study points out pathogenicity differences among Yersinia species, confirms the complex nature of virulence in Y. enterocolitica, and confirms that no single current assay correlates with virulence in Y. enterocolitica.
PMCID: PMC272587  PMID: 6826697
22.  Efficient subtyping of pathogenic Yersinia enterocolitica strains by pulsed-field gel electrophoresis. 
Journal of Clinical Microbiology  1994;32(12):2913-2920.
Yersinia enterocolitica is an enteropathogen that has recently and rapidly expanded over the world. There is a close correlation between the biotypes, serotypes, and phage types of the strains, making it virtually impossible to distinguish isolates of the same serotype with the classical phenotypic markers. In the present study, pulsed-field gel electrophoresis (PFGE) was used to compare the NotI genomic profile (i.e., pulsotype) of 20 strains each of serotypes O:3, O:9, and O:5. Eleven, 12, and 18 different pulsotypes were obtained, respectively, indicating that this technique is very efficient for subtyping pathogenic isolates of Y. enterocolitica. Within strains of serotype O:5, PFGE differentiated two subgroups that corresponded to two biotypes (biotypes 1A and 3). Comparison of the pulsotypes of three strains of biotype 3 and serotype O:3 (referred to as 3/O:3) with those of strains 4/O:3 and 3/O:5 suggested that the pulsotype is closer to the biotype than to the serotype. The pulsotypes of five pairs of strains isolated from the same patient or siblings were also analyzed. In four pairs, the two strains displayed identical pulsotypes, indicating that PFGE might be a powerful epidemiological tool. In the fifth pair, one restriction fragment differed, suggesting that genomic polymorphism may occur in vivo in Y. enterocolitica. Finally, the in vitro genomic stabilities of one strain each of Y. enterocolitica O:3, O:9, and O:5 were investigated. The pulsotypes of 10 isolated colonies were identical within each strain, indicating that in vitro, the genome of Y. enterocolitica is much more stable than that of Y. pestis.
Images
PMCID: PMC264200  PMID: 7883877
23.  The Complete Genome Sequence and Comparative Genome Analysis of the High Pathogenicity Yersinia enterocolitica Strain 8081 
PLoS Genetics  2006;2(12):e206.
The human enteropathogen, Yersinia enterocolitica, is a significant link in the range of Yersinia pathologies extending from mild gastroenteritis to bubonic plague. Comparison at the genomic level is a key step in our understanding of the genetic basis for this pathogenicity spectrum. Here we report the genome of Y. enterocolitica strain 8081 (serotype 0:8; biotype 1B) and extensive microarray data relating to the genetic diversity of the Y. enterocolitica species. Our analysis reveals that the genome of Y. enterocolitica strain 8081 is a patchwork of horizontally acquired genetic loci, including a plasticity zone of 199 kb containing an extraordinarily high density of virulence genes. Microarray analysis has provided insights into species-specific Y. enterocolitica gene functions and the intraspecies differences between the high, low, and nonpathogenic Y. enterocolitica biotypes. Through comparative genome sequence analysis we provide new information on the evolution of the Yersinia. We identify numerous loci that represent ancestral clusters of genes potentially important in enteric survival and pathogenesis, which have been lost or are in the process of being lost, in the other sequenced Yersinia lineages. Our analysis also highlights large metabolic operons in Y. enterocolitica that are absent in the related enteropathogen, Yersinia pseudotuberculosis, indicating major differences in niche and nutrients used within the mammalian gut. These include clusters directing, the production of hydrogenases, tetrathionate respiration, cobalamin synthesis, and propanediol utilisation. Along with ancestral gene clusters, the genome of Y. enterocolitica has revealed species-specific and enteropathogen-specific loci. This has provided important insights into the pathology of this bacterium and, more broadly, into the evolution of the genus. Moreover, wider investigations looking at the patterns of gene loss and gain in the Yersinia have highlighted common themes in the genome evolution of other human enteropathogens.
Synopsis
The goal of this study was to catalogue all the genes encoded within the Y. enterocolitica genome to help us better understand how this bacterium and related bacteria cause different diseases. There are currently genome sequences (complete gene catalogues) available for two other members of this bacterial lineage, which cause dramatically different diseases: Y. pseudotuberculosis, like Y. enterocolitica, is a gut pathogen (enteropathogen) causing gastroenteritis in humans and animals. Yersinia pestis mostly resides within blood (circulating or in fleas following blood meals) and lymph tissue. It causes bubonic plague in humans and animals, and is historically known as “The Black Death.” A three-way comparison of these genomes revealed a patchwork of genes we have defined as being species- or disease-specific and genes that are common to all three Yersinia species. This has provided us with important information on shared gene functions that define the two enteropathogenic yersinias and those that differentiate them. This will help us to connect what we know about the Y. enterocolitica lifestyle within the gut to the disease it causes and its genetic makeup. We have also provided further evidence of gene-loss by Y. pestis as it has evolved from Y. pseudotuberculosis into a more acute systemic pathogen. Similar patterns of gene loss are seen in other important pathogens such as Salmonella enterica serovar Typhi.
doi:10.1371/journal.pgen.0020206
PMCID: PMC1698947  PMID: 17173484
24.  Molecular Analysis of β-Lactamase Genes to Understand their Differential Expression in Strains of Yersinia enterocolitica Biotype 1A 
Scientific Reports  2014;4:5270.
Beta-lactams are used as major therapeutic agents against a number of infectious agents. Due to widespread use of β-lactams, β-lactamases have evolved at a rapid pace leading to treatment failures. Yersinia enterocolitica causes many gastrointestinal problems. It is an extremely heterogeneous species comprising more than fifty serotypes and six biotypes which differ in their ecological niches, geographical distribution and pathogenic potential. Though biotype 1A strains have been associated with outbreaks of Yersiniosis, there has been a controversy regarding their pathogenicity. The strains of Y. enterocolitica isolated from India belonged to biotype 1A and possessed genes for two β-lactamases namely, blaA and blaB. An earlier study by us reported differential expression of blaA by strains of Y. enterocolitica biotype 1A. The present study has been carried out to understand the molecular bases which regulate the expression of blaA in Y. enterocolitica biotype 1A. We concluded that six types of blaA variants were present in strains of biotype 1A. Neither amino acid substitutions in blaA nor mutations in promoter regions of blaA contributed to differential expression of blaA in Y. enterocolitica biotype 1A. Rather, the secondary structures attained by mRNA of blaA might underlie the differential expression of blaA in Y. enterocolitica.
doi:10.1038/srep05270
PMCID: PMC4053712  PMID: 24920253
25.  Virulence and arsenic resistance in Yersiniae. 
Journal of Bacteriology  1997;179(3):612-619.
The genus Yersinia contains three pathogenic species: Yersinia pestis, Y. pseudotuberculosis, and Y. enterocolitica. Only a few biotypes and serotypes of Y. enterocolitica are pathogenic, and these form two distinct groups: some are of low virulence, and they are encountered worldwide; others, mainly encountered in North America, are markedly more virulent. All pathogenic yersiniae possess a 70-kb virulence plasmid called pYV which encodes secreted antihost proteins called Yops as well as a type III secretion machinery that is required for Yop secretion. Genes encoding Yop synthesis and secretion are tightly clustered in three quadrants of the pYV plasmid. We show here that in the low-virulence strains of Y. enterocolitica, the fourth quadrant of the plasmid contains a new class II transposon, Tn2502. This transposon encodes a defective transposase, but transposition can be complemented in trans by Tn2501, another class II transposon. Tn2502 was not detected in the pYV plasmids of the more virulent American strains of Y. enterocolitica, of Y. pseudotuberculosis, and of Y. pestis. Tn2502 confers arsenite and arsenate resistance. This resistance involves four genes; three are homologous to the arsRBC genes present on the Escherichia coli chromosome, but no homolog of the fourth one, arsH, has been found. The systematic presence of such a resistance operon on a virulence plasmid is unusual and could be related to the recent spread of low-virulence Y. enterocolitica strains. The presence of this ars operon also constitutes the first significant difference between the pYV plasmids from different Yersinia species.
PMCID: PMC178738  PMID: 9006011

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