In this study, the prevalence of in wild boars in northeast Germany was determined. For that purpose, the tonsils of 503 wild boars were sampled. The presence of was studied by diagnostic PCR. Positive samples were analyzed by cultural detection using a modified cold enrichment protocol. Ten isolates were obtained, which were characterized by biotyping, molecular serotyping, and multilocus sequence typing (MLST). In addition, whole-genome sequences and the antimicrobial susceptibility of the isolates were analyzed. was isolated from male and female animals, most of which were younger than 1 year. A prevalence of 2% (10/503) was determined by cultural detection, while 6.4% (32/503) of the animals were positive by PCR. The isolates belonged to the biotypes 1 and 2 and serotypes O:1a ( = 7), O:1b ( = 2), and O:4a ( = 1). MLST analysis revealed three sequence types, ST9, ST23, and ST42. Except one isolate, all isolates revealed a strong resistance to colistin. The relationship of the isolates was studied by whole-genome sequencing demonstrating that they belonged to four clades, exhibiting five different pulsed-field gel electrophoresis (PFGE) restriction patterns and a diverse composition of virulence genes. Six isolates harbored the virulence plasmid pYV. Besides two isolates, all isolates contained and genes and a complete or incomplete high-pathogenicity island (HPI). None of them possessed a gene for the superantigen YPM. The study shows that various strains exist in wild boars in northeast Germany, which may pose a risk to humans. is a foodborne pathogen whose occurrence is poorly understood. One reason for this situation is the difficulty in isolating the species. The methods developed for the isolation of are not well suited for We therefore designed a protocol which enabled the isolation of from a relatively high proportion of PCR-positive wild boar tonsils. The study indicates that wild boars in northeast Germany may carry a variety of strains, which differ in terms of their pathogenic potential and other properties. Since wild boars are widely distributed in German forests and even populate cities such as Berlin, they may transmit yersiniae to other animals and crop plants and may thus cause human infections through the consumption of contaminated food. Therefore, the prevalence of should be determined also in other animals and regions to learn more about the natural reservoir of this species.

Yersinia enterocolitica is a zoonotic enteropathogenic bacterium that can cause acute gastroenteritis and mesenteric lymphadenitis. Although Y. enterocolitica is common in animals, food, and the environment, the reservoirs and transmission routes of this pathogen are still not fully understood. The aim of our study was to determine the prevalence of Y. enterocolitica in seafood in Germany, because only limited data are available on that topic. Seafood samples were purchased from retail shops in Berlin, Germany and examined for the presence of Y. enterocolitica by cold enrichment followed by cultivation on selective agar. Presumptive Y. enterocolitica isolates were analyzed by biotyping, serotyping, and antimicrobial susceptibility testing. The total prevalence of Y. enterocolitica in seafood samples was 2.7% (6 of 220 samples). Mussel (2 of 90), shrimp (1 of 89), and cephalopod (3 of 41) samples were positive for Y. enterocolitica. Three isolates were identified as serotype O:8, one was identified as serotype O:5,27, and two samples did not belong to any investigated serotypes. The presence of the virulence-associated genes ail, inv, and ystB was studied by multiplex PCR. Four of the six isolates contained inv and ystB, one produced no positive results for the analyzed genes, and one contained only ystB. All Y. enterocolitica isolates were susceptible to cefotaxime, cefuroxime, chloramphenicol, ciprofloxacin, gentamicin, kanamycin, nalidixic acid, streptomycin, tetracycline, and trimethoprim. Resistance was observed to cephalothin (83.3% of isolates), amoxicillin (83.3%), and ampicillin (50.0%). This study provides the first comprehensive analysis of Y. enterocolitica in retail seafood in Germany. The prevalence found in these seafood samples was comparatively low, and all isolates belonged to biotype 1A. However, seafood contaminated with Y. enterocolitica may pose a risk to consumer health because the pathogenic potential of biotype 1A strains is still being debated.

Yersinia (Y.) enterocolitica and Y. pseudotuberculosis are important zoonotic agents which can infect both humans and animals. To combat these pathogens, the application of strictly lytic phages may be a promising tool. Since only few Yersinia phages have been described yet, some of which demonstrated a high specificity for certain serotypes, we isolated two phages from game animals and characterized them in terms of their morphology, host specificity, lytic activity on two bio-/serotypes and genome composition. The T7-related podovirus vB_YenP_Rambo and the myovirus vB_YenM_P281, which is very similar to a previously described phage PY100, showed a broad host range. Together, they lysed all the 62 tested pathogenic Y. enterocolitica strains belonging to the most important bio-/serotypes in Europe. A cocktail containing these two phages strongly reduced cultures of a bio-/serotype B4/O:3 and a B2/O:9 strain, even at very low MOIs (multiplicity of infection) and different temperatures, though, lysis of bio-/serotype B2/O:9 by vB_YenM_P281 and also by the related phage PY100 only occurred at 37 °C. Both phages were additionally able to lyse various Y. pseudotuberculosis strains at 28 °C and 37 °C, but only when the growth medium was supplemented with calcium and magnesium cations.

Yersinia enterocolitica is a heterogeneous species comprising highly pathogenic, weakly pathogenic and non-pathogenic strains. Previous data suggest that gene exchange may occur in Yersinia. Only scarce information exists about temperate phages of Y. enterocolitica, even though many prophage sequences are present in this species. We have examined 102 pathogenic Y. enterocolitica strains for the presence of inducible prophages by mitomycin C treatment. Ten phages were isolated from nine strains belonging to the bio (B)/serotypes (O) B2/O:5,27, B2/O:9 and 1B/O:8. All phages are myoviruses showing lytic activity only at room temperature. Whole-genome sequencing of the phage genomes revealed that they belong to three groups, which, however, are not closely related to known phages. Group 1 is composed of five phages (type phage: vB_YenM_06.16.1) with genome sizes of 43.8 to 44.9 kb, whereas the four group 2 phages (type phage: vB_YenM_06.16.2) possess smaller genomes of 29.5 to 33.2 kb. Group 3 contains only one phage (vB_YenM_42.18) whose genome has a size of 36.5 kb, which is moderately similar to group 2. The host range of the phages differed significantly. While group 1 phages almost exclusively lysed strains of B2/O:5,27, phages of group 2 and 3 were additionally able to lyse B4/O:3, and some of them even B2/O:9 and 1B/O:8 strains.

Yersinia (Y.) pseudotuberculosis is an important pathogen for both humans and animals. It can infect livestock as well as pets and wild animals. During the last years, a number of reports describe the isolation of Y. pseudotuberculosis from zoo animals, mainly birds and mammals, for which the infection was mostly lethal. Between 2005 and 2019, there were at least 17 cases of deceased mammals belonging to five different species at the Zoo Wuppertal, Germany, which suffered from a Y. pseudotuberculosis infection. Since only scarce information exists on properties of Y. pseudotuberculosis from zoo animals, we characterized eight isolates, covering all infected species, in detail. All of them are members of biotype 1, but belong to five serotypes, five sequence types (STs) and even seven cgMLST types. Using Pulsed-Field Gel Electrophoresis (PFGE) analysis and whole-genome sequencing (WGS), seven isolates could be discriminated from each other. They differ significantly regarding their virulence genes and mobile genetic elements. While the virulence plasmid pYV existed in all serotypes (five isolates), a complete high pathogenicity island (HPI) was detected only in the serotypes O:1a, O:1b and O:13 (four isolates), but not in O:2a and O:2b. Similarly, the content of other plasmids and prophages varies greatly between the isolates. The data demonstrates that the deceased mammals were infected by seven individual isolates and not by a single type predominating in the zoo animals.