Characterization of Yersinia enterocolitica strains potentially virulent for humans and animals in river water

Biological and genomic characterization of three psychrophilic Y. enterocolitica phages

Yersinia (Y.) enterocolitica is an important foodborne pathogenic species that is mainly transmitted by the consumption of contaminated meat, particularly pork. To combat the bacteria along the food chain, the application of strictly lytic phages may be a promising tool. As the temperatures in the gut of animals and during food processing can differ significantly, a phage cocktail intended to be used for applications should comprise phages that are active at various temperatures. In this study, we isolated and characterized three phages with a myoviridal morphology (vB_YenM_P8, vB_YenM_P744 and vB_YenM_P778), which lysed the most important Y. enterocolitica serotypes O:3, O:9 and O:5,27 at a low multiplicity of infection (MOI) and at low temperatures down to 6°C. While vB_YenM_P8 is a member of the T4 family, vB_YenM_P744 and vB_YenM_P778 are novel phages that do not show relationship to known phages. The three phages were mixed in a cocktail with the already described phages vB_YenM_P281 and vB_YenP_Rambo. The cocktail revealed a strong lytic activity and lysed a mixture of Y. enterocolitica serotypes at room temperature (RT) within few hours with a reduction of up to 4.8 log10 units. Moreover, at even lower temperatures the mixture was significantly reduced after incubation overnight. The strongest reductions were determined at 6°C (4.0 log10 units) suggesting that the cocktail can lyse the psychrophilic Y. enterocolitica also during food processing. To determine possible phage resistance, 100 colonies that survived the infection by the phages were isolated and analysed regarding their serotype and phage susceptibility. Most isolates belonged to serotype O:9, but all of them were still sensitive to at least one phage of the cocktail.

Study of Zoonotic Pathogens in Alien Population of Veiled Chameleons (Chamaeleo calyptratus) in the Canary Islands (Spain)

Veiled chameleons (Chamaeleo calyptratus) are native to the Arabian Peninsula that have been introduced as pets in many regions around the world, such as the Canary Islands (Spain). In this work, the gastrointestinal content from veiled chameleons of Gran Canaria island (Canary Islands) has been analyzed to determine the presence of zoonotic bacteria. Forty animals were analyzed using different selective culture media and PCR. The most isolated bacteria were Yersinia enterocolitica (52.4%), followed by Salmonella spp. (40.0%), with positive isolates for Salmonella Tyhpi and Salmonella Typhimurium. Pseudomonas spp. was found in 32.5% of the chameleons. More than half were positive for Pseudomonas aeruginosa. Antibiotic-resistant Staphylococcus spp. was detected in six animals plus one isolate of non-resistant Staphylococcus hominis. Multiple mycobacteria species belonging to both tuberculous and non-tuberculous complexes were identified as well as Escherichia coli carrying the stx₁ and eae virulence genes with 12.5% and 7.5% prevalence, respectively. Listeria monocytogenes, Campylobacter spp., and Vibrio spp. were found in lower proportion (<5%). The results obtained indicate that veiled chameleons in Gran Canaria could be playing a role in the maintenance and dissemination of the pathogens detected, harming public health and biodiversity.

Phage vB_YenS_P400, a Novel Virulent Siphovirus of Yersinia enterocolitica Isolated from Deer

Phage vB_YenS_P400 isolated from deer, is a virulent siphovirus of Y. enterocolitica, whose circularly permutated genome (46,585 bp) is not substantially related to any other phage deposited in public nucleotide databases. vB_YenS_P400 showed a very narrow host range and exclusively lysed two Y. enterocolitica B4/O:3 strains. Moreover, lytic activity by this phage was only discernible at room temperature. Together with the finding that vB_YenS_P400 revealed a long latent period (90 to 100 min) and low burst size (five to ten), it is not suitable for applications but provides insight into the diversity of Yersinia phages.

Detection, characterization, and antimicrobial susceptibility of Yersinia enterocolitica in different types of wastewater in the Czech Republic

AIMS

The purpose of the study was to evaluate the occurrence of Yersinia enterocolitica in different types of wastewater and to characterize the isolates by biotyping, serotyping, and antimicrobial susceptibility testing. In addition, cultivation protocols were evaluated.

METHODS AND RESULTS

The occurrence of Y. enterocolitica was determined in treated and untreated municipal wastewater, as well as in hospital, slaughterhouse, and cowshed wastewater. Y. enterocolitica was detected in 84.1% of the wastewater samples, while the main sources were untreated municipal and slaughterhouse wastewater. In contrast, the lowest incidence was found in hospital wastewater. An exclusive occurrence of biotype 1A (98.3%) was detected. Pathogenic bio-serotypes 4/O:3 and 3/O:3 were isolated only from slaughterhouse wastewater. The highest resistance rates were observed for ampicillin (92.5%) and amoxicillin-clavulanic acid (36.8%).

CONCLUSIONS

Y. enterocolitica was commonly detected in wastewater, although the prevalence varied depending on the origin of the wastewater. No single cultivation protocol was able to recover Y. enterocolitica isolates from such a complex matrix as wastewater.

SIGNIFICANCE AND IMPACT OF THE STUDY

Our study provided data that can contribute to the evaluation of wastewater as a source of Y. enterocolitica and to understanding the threat of wastewater isolates to human health.

Properties of Two Broad Host Range Phages of Yersinia enterocolitica Isolated from Wild Animals

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.

The Prevalence of Yersinia enterocolitica and Yersinia pseudotuberculosis in Small Wild Rodents in Poland

Rodents are a large group of mammals that can be carriers of zoonotic pathogens such as Yersinia strains that cause yersiniosis. The prevalence of Yersinia enterocolitica and Yersinia pseudotuberculosis was determined in 214 small wild rodents from south-eastern Poland. Samples were analyzed by precultivation and PCR. Nine (4.2%) Y. enterocolitica and one (0.5%) Y. pseudotuberculosis isolates were received. Most of them (n = 5) were obtained from the common vole (Microtus arvalis). All Y. enterocolitica strains were classified as biotype (BT) 1A. A PCR analysis of virulence markers revealed that all Y. enterocolitica isolates contained the ystB gene and five isolates harbored a rare genetic combination of ail/ystB. Three of the four ail/ystB-positive isolates belonged to serotype O:5.27. The Y. pseudotuberculosis inv-positive isolate was classified as BT 1. A genetic analysis of Y. enterocolitica harboring the ystB gene revealed 100% similarity between the analyzed sequences and the sequences from diarrhea patients in India and the United Kingdom as well as high similarity with the sequences from different species of wild animals from Poland. The Y. pseudotuberculosis inv sequence was 100% identical to the sequence isolated from fully virulent clinical strain from France and Australia. The results of our study suggest that small wild rodents, especially voles and yellow-necked mice, may act as carriers of Yersinia strains. The high similarity of the tested gene sequences between our isolates and the isolates from other free-living animals indicates that small wild rodents can play a role in the epidemiology of yersiniosis and can shed Yersinia spp. into the environment.

An overview of Yersinia enterocolitica and related species in samples of different origin from San Luis, Argentina

This study is aimed at offering an overview of the prevalence of Yersinia enterocolitica and related species in San Luis, Argentina, from samples of diverse origin received in our laboratory between 1984 and 2014, and providing an analysis of the distribution of Yersinia isolates according to their isolation sources, highlighting bioserotypes and potential reservoirs and vehicles of transmission to humans. From a total of 4572 samples of human, animal, food and environmental origins analyzed by traditional culture methods and molecular techniques, 229 (5%) samples were Yersinia positive. The highest frequency of Yersinia isolates was observed in environmental specimens (14.3%), followed by animal (9.2%), food (5%) and human (0.6%) samples. A total of 255 Yersinia isolates were characterized, including 183 Y. enterocolitica and 72 isolates of other Yersinia species. Biotype 1A associated to several serotypes was identified in Y. enterocolitica isolates from environment (100%), animals (95.5%), foods (71.7%) and human samples (40%); bioserotype 2/O:9 was identified in isolates from foods (25.5%), and biotype 3 was associated with strains from humans (60%), animals (4.5%) and foods (2.8%). This biotype included three strains O:3 and six strains O:5. The data highlight animals and foods as the main Y. enterocolitica sources in our region.

Molecular Characteristics of "BlaB-Like" Chromosomal Inducible Cephalosporinase of Yersinia enterocolitica Biotype 1A Strains

Yersinia enterocolitica biotype 1A strains are emerging pathogens, frequently isolated from clinical samples across the globe. Y. enterocolitica strains produce two chromosomal β-lactamases, BlaA and BlaB. BlaA is a constitutively expressed, Ambler class A, penicillinase, whereas BlaB is Ambler class C-type, inducible cephalosporinase. An earlier study from our laboratory indicated that instead of BlaB, Y. enterocolitica biotype 1A produced a "BlaB-like" enzyme. The objective of this work was to study the molecular characteristics of "Bla-B like" β-lactamases produced by biotype 1A strains to discern their similarity with AmpC-type β-lactamases and the basis of varied levels of minimum inhibitory concentration (MIC) to cefotaxime. Thus, the promoters and blaB genes were investigated in four strains of biotype 1A. Three-dimensional structures of the "BlaB-like" enzymes were modeled, and docked in silico with cefotaxime to understand how specific substitutions in gene sequences affect antibiotic susceptibilities. Our results indicated that all the reported key catalytic residues were present in variants of "Bla-B-like" enzymes, discerned in biotype 1A strains, but at different positions. Molecular docking of enzyme variants with cefotaxime revealed that lesser was the number of the H-binding residues with cefotaxime in a strain, lower was the MIC of cefotaxime in that strain. To the best of our knowledge, this is the first study in which the molecular characteristics and enzymatic interactions of "BlaB-like" cephalosporinases of Y. enterocolitica biotype 1A strains have been reported.

Prevalence and Antimicrobial Resistance of Yersinia enterocolitica in Retail Seafood

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.

Presence of ail and ystB genes in Yersinia enterocolitica biotype 1A isolates from game animals in Poland

The pathogenicity of Yersinia enterocolitica is associated with the presence of plasmid and chromosomal virulence genes. Strains belonging to biotype 1A do not possess pYV plasmids, often harbour the ystB gene and usually lack the ail gene, which is the main virulence marker for Y. enterocolitica. The simultaneous presence of ail and ystB is uncommon. In this study, 21/218 (9.6%) biotype 1A Y. enterocolitica isolates from rectal swabs of wild boar (Sus scrofa; n = 18), red deer (Cervus elaphus; n = 2) and roe deer (Capreolus capreolus; n = 1) in Poland harboured both ail and ystB genes.