Application of fluorescent amplified fragment length polymorphism for comparison of human and animal isolates of Yersinia enterocolitica

Yersinia enterocolitica biovar 1A: An underappreciated potential pathogen in the food chain

Yersinia enterocolitica is an underreported cause of foodborne gastroenteritis. Little is known of the diversity of Y. enterocolitica isolated from food and which food commodities contribute to human disease. In this study, Y. enterocolitica was isolated from 37/50 raw chicken, 8/10 pork, 8/10 salmon and 1/10 leafy green samples collected at retail in the UK. Up to 10 presumptive Y. enterocolitica isolates per positive sample underwent whole genome sequencing (WGS) and were compared with publicly available genomes. In total, 207 Y. enterocolitica isolates were analyzed and belonged to 38 sequence types (STs). Up to five STs of Y. enterocolitica were isolated from individual food samples and isolates belonging to the same sample and ST differed by 0-74 single nucleotide polymorphisms (SNPs). Biotype was predicted for 205 (99 %) genomes that all belonged to biotype 1A, previously described as non-pathogenic. However, around half (51 %) of food samples contained isolates belonging to the same ST as previously isolated from UK human cases. The closest human-derived isolates shared between 17 and 7978 single nucleotide polymorphisms (SNPs) with the food isolates. Extensive food surveillance is required to determine what food sources are responsible for Y. enterocolitica infections and to re-examine the role of biotype 1A as a human pathogen.

Yersinia enterocoliticainfections associated with improperly pasteurized milk products: southwest Pennsylvania, March–August, 2011

In July 2011, a cluster ofYersinia enterocoliticainfections was detected in southwestern Pennsylvania, USA. We investigated the outbreak's source and scope in order to prevent further transmission. Twenty-two persons were diagnosed with yersiniosis; 16 of whom reported consuming pasteurized dairy products from dairy A. Pasteurized milk and food samples were collected from this dairy.Y. enterocoliticawas isolated from two products. Isolates from both food samples and available clinical isolates from nine dairy A consumers were indistinguishable by pulsed-field gel electrophoresis. Environmental and microbiological investigations were performed at dairy A and pasteurization deficiencies were noted. Because consumption of pasteurized milk is common and outbreaks have the potential to become large, public health interventions such as consumer advisories or closure of the dairy must be implemented quickly to prevent additional cases if epidemiological or laboratory evidence implicates pasteurized milk as the outbreak source.

Scientific Opinion on the public health hazards to be covered by inspection of meat from sheep and goats

A risk ranking process identified Toxoplasma gondii and pathogenic verocytotoxin-producing Escherichia coli (VTEC) as the most relevant biological hazards for meat inspection of sheep and goats. As these are not detected by traditional meat inspection, a meat safety assurance system using risk-based interventions was proposed. Further studies are required on T. gondii and pathogenic VTEC. If new information confirms these hazards as a high risk to public health from meat from sheep or goats, setting targets at carcass level should be considered. Other elements of the system are risk-categorisation of flocks/herds based on improved Food Chain Information (FCI), classification of abattoirs according to their capability to reduce faecal contamination, and use of improved process hygiene criteria. It is proposed to omit palpation and incision from post-mortem inspection in animals subjected to routine slaughter. For chemical hazards, dioxins and dioxin-like polychlorinated biphenyls were ranked as being of high potential concern. Monitoring programmes for chemical hazards should be more flexible and based on the risk of occurrence, taking into account FCI, which should be expanded to reflect the extensive production systems used, and the ranking of chemical substances, which should be regularly updated and include new hazards. Control programmes across the food chain, national residue control plans, feed control and monitoring of environmental contaminants should be better integrated. Meat inspection is a valuable tool for surveillance and monitoring of animal health and welfare conditions. Omission of palpation and incision would reduce detection effectiveness for tuberculosis and fasciolosis at animal level. Surveillance of tuberculosis at the slaughterhouse in small ruminants should be improved and encouraged, as this is in practice the only surveillance system available. Extended use of FCI could compensate for some, but not all, the information on animal health and welfare lost if only visual post-mortem inspection is applied.

Genotypic Characterization of Yersinia enterocolitica Biotype 4/O:3 Isolates from Pigs and Slaughterhouses Using SE-AFLP, ERIC-PCR, and PFGE

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.

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.

Behavior of Yersinia enterocolitica in Foods

Yersinia enterocolitica are ubiquitous, being isolated frequently from soil, water, animals, and a variety of foods. They comprise a biochemically heterogeneous group that can survive and grow at refrigeration temperatures. The ability to propagate at refrigeration temperatures is of considerable significance in food hygiene. Virulent strains of Yersinia invade mammalian cells such as HeLa cells in tissue culture. Two chromosomal genes, inv and ail, were identified for cell invasion of mammalian. The pathogen can cause diarrhoea, appendicitis and post-infection arthritis may occur in a small proportion of cases. The most common transmission route of pathogenic Y. enterocolitica is thought to be fecal-oral via contaminated food. Direct person-to-person contact is rare. Occasionally, pathogenic Y. enterocolitica has been detected in vegetables and environmental water; thus, vegetables and untreated water are also potential sources of human yersiniosis. However, the isolation rates of pathogenic Y. enterocolitica have been low, which may be due to the limited sensitivity of the detection methods. To identify other possible transmission vehicles, different food items should be studied more extensively. Many factors related to the epidemiology of Y. enterocolitica, such as sources, transmission routes, and predominating genotypes remain obscure because of the low sensitivity of detection methods.

Yersinia enterocolitica: Epidemiological Studies and Outbreaks

Yersinia enterocolitica is the most common bacteriological cause of gastrointestinal disease in many developed and developing countries. Although contaminated food is the main source of human infection due to Y. enterocolitica, animal reservoir and contaminated environment are also considered as other possible infection sources for human in epidemiological studies. Molecular based epidemiological studies are found to be more efficient in investigating the occurrence of human pathogenic Y. enterocolitica in natural samples, in addition to conventional culture based studies.

Yersinia enterocolitica: Mode of Transmission, Molecular Insights of Virulence, and Pathogenesis of Infection

Although Yersinia enterocolitica is usually transmitted through contaminated food and untreated water, occasional transmission such as human-to-human, animal-to-human and blood transfusion associated transmission have also identified in human disease. Of the six Y. enterocolitica biotypes, the virulence of the pathogenic biotypes, namely, 1B and 2-5 is attributed to the presence of a highly conserved 70-kb virulence plasmid, termed pYV/pCD and certain chromosomal genes. Some biotype 1A strains, despite lacking virulence plasmid (pYV) and traditional chromosomal virulence genes, are isolated frequently from humans with gastrointestinal diseases similar to that produced by isolates belonging known pathogenic biotypes. Y. enterocolitica pathogenic biotypes have evolved two major properties: the ability to penetrate the intestinal wall, which is thought to be controlled by plasmid genes, and the production of heat-stable enterotoxin, which is controlled by chromosomal genes.

Genetic relationships between clinical and non-clinical strains of Yersinia enterocolitica biovar 1A as revealed by multilocus enzyme electrophoresis and multilocus restriction typing

Background

Genetic relationships among 81 strains of Y. enterocolitica biovar 1A isolated from clinical and non-clinical sources were discerned by multilocus enzyme electrophoresis (MLEE) and multilocus restriction typing (MLRT) using six loci each. Such studies may reveal associations between the genotypes of the strains and their sources of isolation.

Results

All loci were polymorphic and generated 62 electrophoretic types (ETs) and 12 restriction types (RTs). The mean genetic diversity (H) of the strains by MLEE and MLRT was 0.566 and 0.441 respectively. MLEE (DI = 0.98) was more discriminatory and clustered Y. enterocolitica biovar 1A strains into four groups, while MLRT (DI = 0.77) identified two distinct groups. BURST (Based Upon Related Sequence Types) analysis of the MLRT data suggested aquatic serotype O:6,30-6,31 isolates to be the ancestral strains from which, clinical O:6,30-6,31 strains might have originated by host adaptation and genetic change.

Conclusion

MLEE revealed greater genetic diversity among strains of Y. enterocolitica biovar 1A and clustered strains in four groups, while MLRT grouped the strains into two groups. BURST analysis of MLRT data nevertheless provided newer insights into the probable evolution of clinical strains from aquatic strains.

Multilocus variable number tandem repeat analysis as a tool to discern genetic relationships among strains of Yersinia enterocolitica biovar 1A

AIMS

To identify variable number tandem repeat (VNTR)-containing loci, and to use multilocus VNTR (MLVA) to discern genetic relationships among strains of Yersinia enterocolitica biovar 1A isolated from diverse sources.

METHODS AND RESULTS

The whole genome sequence of Y. enterocolitica 8081 was analysed and eight VNTR loci with repeat sizes between 4 and 9 bp, and each containing more than four repeat copies were selected for MLVA typing of 88 strains of Y. enterocolitica. Of these, four loci were polymorphic and generated 26 MLVA genotypes among 81 strains of Y. enterocolitica biovar 1A. MLVA was found to be quite discriminatory (DI = 0.87). Cluster analysis and population modelling using minimum spanning tree (MST) clearly clustered Y. enterocolitica biovar 1A into two major groups.

CONCLUSIONS

The MLVA is easy to perform and can be used to discern clonal relationship among strains of Y. enterocolitica. Also the phylogenetic relationships obtained with MLVA genotypes were in good agreement with those established by other typing methods.

SIGNIFICANCE AND IMPACT OF THE STUDY

The MLVA method reported is relatively more discriminatory than the other genotyping methods and has the potential to be used as an epidemiological tool for the study of strains of Y. enterocolitica biovar 1A.

Polyphasic characterization of Xanthomonas axonopodis pv. allii associated with outbreaks of bacterial blight on three Allium species in the Mascarene archipelago

Based on the number of new reports during the last two decades, bacterial blight of onion (Allium cepa) is considered an emerging disease. The causal agent, Xanthomonas axonopodis pv. allii, is pathogenic to several Allium species after inoculation, but outbreaks worldwide have been primarily reported on onion. We describe a unique epidemiological situation in Réunion Island, France, with concomitant outbreaks on three Allium species, onion, leek (A. porrum), and garlic (A. sativum). There was no host specialization within Allium spp. among strains associated with the three host species. Based on amplified fragment length polymorphism (AFLP) and restriction fragment length polymorphism, strains associated with these outbreaks in Réunion Island were highly related genetically to strains isolated from diseased plant samples and contaminated seed lots in the neighboring island of Mauritius, where the disease has occurred since 1984. All AFLP haplotypes were identified as X. axonopodis pv. allii based on polymerase chain reaction analysis using specific primers, biochemical tests, and/or pathogenicity tests. Two genetically related groups of strains (A and B) that can be distinguished by AFLP, differential utilization of three carbon sources, and xanthomonadin pigment production were detected initially after establishment of the pathogen. In less than 10 years after the establishment of the pathogen there was nearly an extinction of group A strains in Réunion Island, suggesting differences in fitness between strains in the two groups.

Prevalence of pathogenic Yersinia enterocolitica in pigs slaughtered at a Swiss abattoir

Human yersiniosis is the third most common enteric disease after campylobacteriosis and salmonellosis in many European countries. However, epidemiological data on the prevalence of pathogenic Yersinia enterocolitica in animals and humans is insufficient. Pigs are assumed to be the main reservoir of pathogenic Y. enterocolitica because pig is so far the only animal species from which pathogenic strains have frequently been isolated. This work was conducted to study the frequency of ail-positive Y. enterocolitica in pigs slaughtered at a Swiss abattoir. In total, 212 pig tonsils were screened by real-time PCR and culture methods. The prevalence rate of ail-positive Y. enterocolitica in pigs at slaughter was 88% and 34% with PCR and culture methods, respectively. The 148 ail-positive isolates from the 72 culture-positive tonsils were bio-and serotyped. The most common bioserotype was 4/O:3 found in 96% (69/72) of the culture-positive samples. However, pig was also shown to be a reservoir for ail-positive Y. enterocolitica belonging to bioserotypes 2/O:5,27 and 2/O:9, which were detected in 8% (6/72) and 1% (1/72) of the culture-positive samples, respectively. Using PFGE with NotI, only a limited number of different patterns was found. In all, 6 genotypes were obtained when 86 isolates of bioserotype 4/O:3 from 69 samples were characterised and two genotypes (N1 and N4) dominated. The biotype 4 differs clearly from biotype 2 with PFGE. Antimicrobial resistance testing of 77 ail-positive Y. enterocolitica isolates from 72 samples studied with disc-diffusion revealed that all strains were sensitive to cefotaxime, chloramphenicol, ciprofloxacin and tetracycline, which are antimicrobial agents used for treatment of human disease. The isolates of bioserotype 2/O:5,27 differed from the isolates of bioserotypes 2/O:9 and 4/O:3 in resistance to ampicillin and amoxicillin/clavulanic acid.

Development of multiple-locus variable-number tandem-repeat analysis for Yersinia enterocolitica subsp. palearctica and its application to bioserogroup 4/O3 subtyping

Yersinia enterocolitica bioserogroup 4/O3 is the predominant causative agent of yersiniosis in Europe and North America. Multiple-locus variable-number tandem-repeat analysis (MLVA) was developed to improve the resolution power of classical genotyping methods. MLVA based on six loci was able to distinguish 76 genotypes among 91 Y. enterocolitica isolates of worldwide origin and 41 genotypes among 51 nonepidemiologically linked bioserogroup 4/O3 isolates, proving that it has a high resolution power. However, only a slight correlation of the MLVA genotypes and the geographic distribution of the isolates was observed. Although MLVA was also capable of distinguishing strains of Y. enterocolitica subsp. palearctica O9 and O5,27, there was only a minor correlation between the MLVA genotypes and serogroups. MLVA may be a helpful tool for epidemiological investigations of Y. enterocolitica subsp. palearctica outbreaks.

An aflagellate mutant Yersinia enterocolitica biotype 1A strain displays altered invasion of epithelial cells, persistence in macrophages, and cytokine secretion profiles in vitro

Despite being classically defined as non-pathogenic, there is growing evidence that biotype 1A Yersinia enterocolitica isolates may be aetiological agents of disease in humans. In previous studies, a potential link between motility and the ability of biotype 1A strains to invade cultured epithelial cells was observed. In an attempt to further investigate this finding, a flagella mutant was constructed in a human faecal Y. enterocolitica biotype 1A isolate. The flagella mutation abolished the ability of the strain to invade cultured human epithelial cells, although adherence was not affected. The aflagellate mutant was also attenuated in its ability to survive within cultured macrophages, being cleared after 3 h, whilst the wild-type persisted for 24 h after infection. Examination of cytokine secretion by infected macrophages also suggested that the flagella of biotype 1A strains act as anti-inflammatory agents, decreasing production of tumour necrosis factor (TNF)-alpha whilst increasing secretion of interleukin (IL)-10. Preliminary studies using porcine in vitro organ culture (IVOC) tissue suggested that the flagella mutant was also attenuated in its ability to colonize intestinal tissue.

The rrn locus and gyrB genotyping confirm the existence of two clonal groups in strains of Yersinia enterocolitica subspecies palearctica biovar 1A

Eighty-one strains of Yersinia enterocolitica biovar 1A representing several serotypes isolated from India, France, Germany and the USA were analyzed using ribotyping, 16S-23S rDNA intergenic spacer length polymorphism analysis (PCR-ribotyping) and gyrB restriction fragment length polymorphism. Ribotyping with BglI, NciI and EcoRV distinguished 81 strains into 4, 3 and 2 ribotypes respectively. BglI-NciI combination gave the highest Simpson's diversity index (DI=0.43). Strains with identical ribotypes were further differentiated by PCR-ribotyping. The combination of BglI-NciI ribotyping with PCR ribotyping increased DI to 0.72. This suggested that the combination of the two may be used for molecular epidemiological studies of Y. enterocolitica biovar 1A. This approach clearly resolved the strains into two clonal groups, each comprising strains isolated from humans, swine, pork and wastewater. PCR-RFLP of the gyrB gene using three enzymes (AluI, MspI and HinfI) distinguished strains into seven types and confirmed the existence of two clonal groups. Thus, assessment of heterogeneity based on chromosomal restriction analysis (ribotyping), rRNA spacer length polymorphism (PCR-ribotyping) and gyrB gene analysis were in concordance and provided unequivocal evidence for the presence of two groups amongst strains of Y. enterocolitica biovar 1A despite their diverse geographic origins. These data also grouped clinical and non-clinical strains of serotype O:6,30-6,31 into discrete subgroups.

Distribution of virulence-associated genes inYersinia enterocoliticabiovar 1A correlates with clonal groups and not the source of isolation

Yersinia enterocolitica, an important food- and water-borne enteric pathogen, is represented by six biovars viz. 1A, 1B and 2-5. Some biovar 1A strains, despite lacking virulence plasmid (pYV) and chromosomal virulence genes, have been reported to cause symptoms similar to that produced by isolates belonging to known pathogenic biovars. Virulence-associated genes viz. ail, virF, inv, myfA, ystA, ystB, ystC, tccC, hreP, fepA, fepD, fes, ymoA and sat were studied in 81 clinical and nonclinical strains of Y. enterocolitica biovar 1A by PCR amplification. All strains lacked ail, virF, ystA and ystC genes. The distribution of other genes with respect to clonal groups revealed that four genes viz. ystB, hreP, myfA and sat were associated exclusively with strains belonging to clonal group A. The clonal groups A and B were differentiated previously based on rep (REP-/ERIC) - PCR genomic fingerprinting. The distribution of virulence-associated genes, however, did not differ significantly between clinical and nonclinical strains. In strains of Y. enterocolitica biovar 1A, clonal groups seem to reflect virulence potential better than the source (clinical vs. nonclinical) of isolation.

Yersinia enterocolitica isolates of differing biotypes from humans and animals are adherent, invasive and persist in macrophages, but differ in cytokine secretion profiles in vitro

Previous epidemiological studies have demonstrated a potential link between the serotypes of Yersinia enterocolitica recovered from cattle, sheep and pigs and those isolated from human disease cases. Further studies utilizing amplified fragment length polymorphisms have shown a relationship at the genetic level between strains of biotypes 3 and 4 from humans and livestock, and also suggested that some biotype 1A isolates, classically defined as non-pathogenic, are closely related to biotype 3 and 4 isolates. This study sought to understand further the pathogenic potential of Y. enterocolitica isolates from livestock in Great Britain. A range of surrogate in vitro models, such as invasion of epithelial tissue cultures, survival in cultured macrophages and cytokine secretion response, was employed to assess the pathogenicity of 88 strains. The results suggested that all isolates examined were capable of adhering to and invading epithelial cells and of surviving within macrophages. However, the inflammatory response of the infected macrophages differed with the infecting Y. enterocolitica subtype, with the response to pathogenic biotype 3 and 4 isolates different to that observed with biotype 1A isolates, and with the biotype 3 O : 5,27 isolates recovered exclusively from animals. Infections of porcine tissue also suggested the possibility of host-tissue tropism within Y. enterocolitica subtypes.

Molecular epidemiology of Yersinia enterocolitica infections

Yersinia enterocolitica is an important food-borne pathogen that can cause yersiniosis in humans and animals. The epidemiology of Y. enterocolitica infections is complex and remains poorly understood. Most cases of yersiniosis occur sporadically without an apparent source. The main sources of human infection are assumed to be pork and pork products, as pigs are a major reservoir of pathogenic Y. enterocolitica. However, no clear evidence shows that such a transmission route exists. Using PCR, the detection rate of pathogenic Y. enterocolitica in raw pork products is high, which reinforces the assumption that these products are a transmission link between pigs and humans. Several different DNA-based methods have been used to characterize Y. enterocolitica strains. However, the high genetic similarity between strains and the predominating genotypes within the bio- and serotype have limited the benefit of these methods in epidemiological studies. Similar DNA patterns have been obtained among human and pig strains of pathogenic Y. enterocolitica, corroborating the view that pigs are an important source of human yersiniosis. Indistinguishable genotypes have also been found between human strains and dog, cat, sheep and wild rodent strains, indicating that these animals are other possible infection sources for humans.

Genotyping of human and porcine Yersinia enterocolitica, Yersinia intermedia, and Yersinia bercovieri strains from Switzerland by amplified fragment length polymorphism analysis

In this study, 231 strains of Yersinia enterocolitica, 25 strains of Y. intermedia, and 10 strains of Y. bercovieri from human and porcine sources (including reference strains) were analyzed using amplified fragment length polymorphism (AFLP), a whole-genome fingerprinting method for subtyping bacterial isolates. AFLP typing distinguished the different Yersinia species examined. Representatives of Y. enterocolitica biotypes 1A, 1B, 2, 3, and 4 belonged to biotype-related AFLP clusters and were clearly distinguished from each other. Y. enterocolitica biotypes 2, 3, and 4 appeared to be more closely related to each other (83% similarity) than to biotypes 1A (11%) and 1B (47%). Biotype 1A strains exhibited the greatest genetic heterogeneity of the biotypes studied. The biotype 1A genotypes were distributed among four major clusters, each containing strains from both human and porcine sources, confirming the zoonotic potential of this organism. The AFLP technique is a valuable genotypic method for identification and typing of Y. enterocolitica and other Yersinia spp.

Sporadic human Yersinia enterocolitica infections caused by bioserotype 4/O : 3 originate mainly from pigs

Yersinia enterocolitica 4/O : 3 is the most frequent cause of sporadic human yersiniosis in Finland and Germany. To investigate the possible link between pigs and humans, 282 human and 534 porcine strains from Finland and Germany were characterized with PFGE using NotI, ApaI and XhoI enzymes. Most of the human strains (>80 %) were indistinguishable from the porcine strains in both countries and most of the genotypes (178/182) were different in Finland and Germany. The indistinguishable genotypes among human and porcine strains together with different genotypes in Finland and Germany indicate that pigs are an important source of sporadic yersiniosis in both countries.