Evaluation of ribotyping as a tool for molecular typing of Yersinia pseudotuberculosis strains of worldwide origin

INDEL-Typing of <i>Yersinia pseudotuberculosis</i> Strains

The aim of this study was to develop a new method of intraspecific genetic differentiation of Yersinia pseudotuberculosis, based on the detection of INDEL-markers using PCR. Materials and methods. Analyzed were 308 strains from the NCBI database and 15 strains sequenced within the frames of this study. The nucleotide sequences of the strains were determined using the MiSeq technology platform. The genomes of the strains sequenced in the work, as well as genomes from the NCBI database, were assessed using in silico PCR with 7 pairs of primers designed in the study. As a result of a comparison of genome-wide sequences of 22 Y. pseudotuberculosis strains from the NCBI database, using the author’s software (GenExpert), 7 INDEL-markers were selected that make it possible to effectively distinguish between strains of the causative agent of pseudotuberculosis. Based on these markers, 7 pairs of primers were designed and synthesized for the analysis of different strains using PCR. Analysis of 323 strains in PCR in silico and 70 strains in PCR in vitro allowed for dividing them into 30 genetic groups. Comparison of the results of PCR in silico and in vitro confirmed the possibility of using the proposed primers for intraspecific differentiation of Y. pseudotuberculosis. Based on the data obtained, a dendrogram reflecting the phylogenetic relations of different strains of Y. pseudotuberculosis was constructed. When analyzing the distribution of Y. pseudotuberculosis strains by various clusters and genetic groups, a number of patterns were revealed. Conducted in silico and in vitro PCR show that the proposed method of INDEL-typing can be used for intraspecific genetic differentiation of the causative agent of pseudotuberculosis.

Loop-mediated isothermal amplification assays for detecting Yersinia pseudotuberculosis in milk powders

Yersinia pseudotuberculosis is a Gram-negative foodborne pathogen that causes several diseases, such as enteritis, septicemia, and reactive arthritis. Loop-mediated isothermal amplification (LAMP) assay targeting the 16S-23S rDNA internal transcribed spacer (ITS) region was developed to detect Y. pseudotuberculosis in milk powder. The DNA amplification could be completed in 1 h, and detected by produced white precipitate visible to naked eyes. The detection limit of LAMP assay was 10(0) fg/reaction for genomic DNA, and 10(0) CFU/100 g milk powder coupled with 12 h enrichment. LAMP assay is 100 times more sensitive than conventional polymerase chain reaction method for detecting Y. pseudotuberculosis, and correctly identified 18 cases of Y. pseudotuberculosis contaminations from 236 commercial milk powder products. In conclusion, the developed LAMP assay may facilitate rapid detection of Y. pseudotuberculosis contaminations in agricultural and food products.

PRACTICAL APPLICATION

Rapid and accurate detection of Yersinia pseudotuberculosis in milk products.

Typing and clustering of Yersinia pseudotuberculosis isolates by restriction fragment length polymorphism analysis using insertion sequences

Yersinia pseudotuberculosis is an enteropathogen that has an animal reservoir and causes human infections, mostly in temperate and cold countries. Most of the methods previously used to subdivide Y. pseudotuberculosis were performed on small numbers of isolates from a specific geographical area. One aim of this study was to evaluate the typing efficiency of restriction fragment length polymorphism of insertion sequence hybridization patterns (IS-RFLP) compared to other typing methods, such as serotyping, ribotyping, and multilocus sequence typing (MLST), on the same set of 80 strains of Y. pseudotuberculosis of global origin. We found that IS100 was not adequate for IS-RFLP but that both IS285 and IS1541 efficiently subtyped Y. pseudotuberculosis. The discriminatory index (DI) of IS1541-RFLP (0.980) was superior to those of IS285-RFLP (0.939), ribotyping (0.944), MLST (0.861), and serotyping (0.857). The combination of the two IS (2IS-RFLP) further increased the DI to 0.998. Thus, IS-RFLP is a powerful tool for the molecular typing of Y. pseudotuberculosis and has the advantage of exhibiting well-resolved banding patterns that allow for a reliable comparison of strains of worldwide origin. The other aim of this study was to assess the clustering power of IS-RFLP. We found that 2IS-RFLP had a remarkable capacity to group strains with similar genotypic and phenotypic markers, thus identifying robust populations within Y. pseudotuberculosis. Our study thus demonstrates that 2IS- and even IS1541-RFLP alone might be valuable tools for the molecular typing of global isolates of Y. pseudotuberculosis and for the analysis of the population structure of this species.

Distribution of virF/lcrF-positive Yersinia pseudotuberculosis serotype O:3 at farm level

The distribution and persistence of pathogenic, virF/lcrF-positive Yersinia pseudotuberculosis were investigated in pigs and in the pig house environment during rearing to determine possible contamination routes of early infections. Based on Y. pseudotuberculosis-positive tonsils of slaughter pigs in our previous study, Y. pseudotuberculosis-positive animals were traced back to the farms. Eight farms were visited from 6-10 months later, and a total of 155 pooled and six individual faecal samples from pigs and 116 pooled environmental samples were collected for analysis by different culture methods. Four of the eight farms were found to be Y. pseudotuberculosis-positive. All positive faecal samples were obtained from fattening pigs, with prevalence varying from 5% to 71% on positive farms. Sows, boars and suckling piglets were Y. pseudotuberculosis-negative on all farms. Most Y. pseudotuberculosis-positive farms (three of four) were on a one-site production system, which had a higher prevalence of Y. pseudotuberculosis (5-26%) among fattening pigs than the all-in, all-out system (1-5%). All Y. pseudotuberculosis isolates belonged to serotype O:3 and carried the virF/lcrF gene on the virulence plasmid. Biotypes 2 and 3 were involved, the latter in one isolate and not being previously reported in pigs. Altogether 53 isolates from 16 positive samples were characterized with pulsed-field gel electrophoresis (PFGE). Using SpeI, NotI and XbaI enzymes, four, three and two different PFGE patterns were obtained respectively. A total of nine different genotypes were identified when the profiles of the enzymes were combined. The most common genotypes were gIV, found on three, and gXII, found on two of the four Y. pseudotuberculosis-positive farms. The same genotypes previously detected in pig tonsils were present in pig faeces from the same farm, indicating that some Y. pseudotuberculosis strains can persist in the pig house environment.

Yersinia pseudotuberculosis infection in a suckler calf in the United Kingdom: a case report

Enterocolitis caused by Yersinia pseudotuberculosis was identified by bacterial culture and histopathology in a 5-month old suckler calf. No other significant enteric pathogens were detected. Diagnosis of this condition can be missed if selective media are not used for bacteriology and if histopathology is not attempted or the alimentary tract is unsuitable for examination. This is the first case report of Y. pseudotuberculosis infection in a calf in the United Kingdom.

Oral inoculation with Type III secretion mutants of Yersinia pseudotuberculosis provides protection from oral, intraperitoneal, or intranasal challenge with virulent Yersinia

The enteric pathogen Yersinia pseudotuberculosis (Yptb) causes gastroenteritis, mesenteric lymphadenitis, and systemic infections in humans, livestock, and wild animals. Yptb Type III secretion system (pTTSS) mutants efficiently colonize lymphoid tissues, but not the gastrointestinal tract, spleen, or liver. Here, we show that a single oral inoculation of pTTSS mutants prevents morbidity in almost 100% of mice challenged intragastrically with virulent Yptb. In addition, a single oral inoculation of a pTTSS mutant protected 50% of mice challenged intraperitoneally or intranasally with virulent Yptb. In addition, the intranasally challenged mice that succumbed to infection lived significantly longer than non-immunized mice. Thus, pTTSS mutants can function as live attenuated vaccine when delivered orally. Potential uses for these attenuated strains include use as a livestock vaccine, a rodent plague control reagent in endemic areas around the world, and a vector for delivery of other antigens to the mesenteric lymph nodes.