Clinical manifestations of Yersinia pseudotuberculosis infection in children

Enteric Infection-Associated Reactive Arthritis: A Systematic Review and Meta-Analysis

Background. The objective of this systematic review and meta-analysis was to estimate the proportions of individuals infected with Campylobacter, Escherichia, Salmonella, Shigella, or Yersinia who develop reactive arthritis. Methods. A systematic review was conducted, encompassing English-language articles published before January 2024, sourced from the Embase, PubMed, Scopus, and Web of Science databases. This review included observational studies that reported the occurrence of reactive arthritis (ReA) among patients with Campylobacter, Escherichia, Salmonella, Shigella, or Yersinia infections. Data extraction was carried out independently by two reviewers. Subsequently, a random-effects meta-analysis was performed, with heterogeneity assessed using the I2 value. Additionally, meta-regression was employed to investigate the potential influence of study-level variables on the observed heterogeneity. Results. A total of 87 studies were identified; 23 reported on ReA development after Campylobacter infection, 7 reported on ReA after Escherichia infection, 30 reported ReA onset after salmonellosis, 14 reported ReA after shigellosis, and 13 reported ReA after Yersinia infection. The proportion of Campylobacter patients who developed ReA was 0.03 (95% CI [0.01, 0.06], I2 = 97.62%); the proportion of Escherichia patients who developed ReA was 0.01 (95% CI [0.00, 0.06], I2 = 92.78%); the proportion of Salmonella patients was 0.04 (95% CI [0.02, 0.08], I2 = 97.67%); the proportion of Shigella patients was 0.01 (95% CI [0.01, 0.03], I2 = 90.64%); and the proportion of Yersinia patients who developed ReA was 0.05 (95% CI [0.02, 0.13], I2 = 96%). Conclusion. A significant proportion of Salmonella, Shigella, and Yersinia cases resulted in ReA. Nonetheless, it is important to interpret the findings cautiously due to the substantial heterogeneity observed between studies.

First Description of a Yersinia pseudotuberculosis Clonal Outbreak in France, Confirmed Using a New Core Genome Multilocus Sequence Typing Method

Yersinia pseudotuberculosis is an enteric pathogen causing mild enteritis that can lead to mesenteric adenitis in children and septicemia in elderly patients. Most cases are sporadic, but outbreaks have already been described in different countries. We report for the first time a Y. pseudotuberculosis clonal outbreak in France, that occurred in 2020. An epidemiological investigation based on food queries pointed toward the consumption of tomatoes as the suspected source of infection. The Yersinia National Reference Laboratory (YNRL) developed a new cgMLST scheme with 1,921 genes specific to Y. pseudotuberculosis that identified the clustering of isolates associated with the outbreak and allowed to perform molecular typing in real time. In addition, this method allowed to retrospectively identify isolates belonging to this cluster from earlier in 2020. This method, which does not require specific bioinformatic skills, is now used systematically at the YNRL and proves to display an excellent discriminatory power and is available to the scientific community. IMPORTANCE We describe in here a novel core-genome MLST method that allowed to identify in real time, and for the first time in France, a Y. pseudotuberculosis clonal outbreak that took place during the summer 2020 in Corsica. Our method allows to support epidemiological and microbiological investigations to establish a link between patients infected with closely associated Y. pseudotuberculosis isolates, and to identify the potential source of infection. In addition, we made this method available for the scientific community.

Pan-genomics, drug candidate mining and ADMET profiling of natural product inhibitors screened against Yersinia pseudotuberculosis

Yersinia pseudotuberculosis belongs to the family Enterobacteriaceae and is responsible for scarlatinoid fever, food poisoning, post-infectious complications like erythema nodosum/reactive arthritis as well as pseudoappendicitis in children. Genome sequences of the 23 whole genomes from NCBI were utilized for conducting the pan-genomic analysis. Essential proteins from the core region were obtained and drug targets were identified using a hierarchal in silico approach. Among these, multidrug resistance protein sub-unit mdtC was chosen for further analysis. This protein unit confers resistance to antibiotics upon forming a tripartite complex with units A and B in Escherichia coli. Details of the function have not yet been elucidated experimentally in Yersinia spp. Computational structure modeling and validation were followed by screening against phytochemical libraries of traditional Indian (Ayurveda), North African, and traditional Chinese flora using Molecular Operating Environment software version 2019.0102. ADMET profiling and descriptor study of best docked compounds was studied. Since phytotherapy is the best resort to antibiotic resistance so these compounds should be tested experimentally to further validate the results. The obtained information could aid wet-lab scientists to work on the scaffold of screened drug-like compounds from natural resources. This could be useful in our quest for antibiotic-resistant therapy against Y. pseudotuberculosis.

Far Eastern Scarlet-Like Fever is a Special Clinical and Epidemic Manifestation of Yersinia pseudotuberculosis Infection in Russia

Pseudotuberculosis in humans until the 1950s was found in different countries of the world as a rare sporadic disease that occurred in the form of acute appendicitis and mesenteric lymphadenitis. In Russia and Japan, the Yersinia pseudotuberculosis (Y. pseudotuberculosis) infection often causes outbreaks of the disease with serious systemic inflammatory symptoms, and this variant of the disease has been known since 1959 as Far Eastern Scarlet-like Fever (FESLF). Russian researchers have proven that the FESLF pathogen is associated with a concrete clonal line of Y. pseudotuberculosis, characterized by a specific plasmid profile (pVM82, pYV 48 MDa), sequence (2ST) and yadA gene allele (1st allele). This review summarized the most important achievements in the study of FESLF since its discovery in the Far East. It has been established that the FESLF causative agent is characterized by a unique phenomenon of psychrophilicity, which consists of its ability to reproduce in the environment with its biologically low and variable temperature (4-12 °C), at which the pathogen multiplies and accumulates while maintaining or increasing its virulence, which ensures the emergence and development of the epidemic process. The key genetic and biochemical mechanisms of Y. pseudotuberculosis adaptation to changing environmental conditions were characterized, and the morphological manifestations of the adaptive variability of these bacteria in different conditions of their habitat were revealed. The main features of the pathogenesis and morphogenesis of FESLF, including those associated with the Y. pseudotuberculosis toxigenicity, were presented. The pathogenetic value of the plasmid PVM82, found only in the FESLF pathogen, was shown.

Yersinia pseudotuberculosis infection intractable by antibiotics: A rare case report

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Yersinia pseudotuberculosis infection is usually cured only by administering antibiotics.

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The operation must have been performed for this patient because of persistent Yersinia pseudotuberculosis infection.

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Early diagnosis and administering antibiotics are important for Yersinia pseudotuberculosis infection to avoid unnecessary operations.

Introduction

Yersinia pseudotuberculosis infection is usually cured spontaneously or with administration of antibiotics.

Presentation of case

The patient is a twelve-year-old boy with right lower quadrant pain who had enterocolitis one month previously. Contrast-enhanced abdominal computed tomography showed a distended and edematous ileum and an intra-abdominal abscess adjacent to the mesentery with a normal appendix. The patient’s general condition did not improve with antibiotics, so an ileocecectomy was performed.

Discussion

Yersinia pseudotuberculosis infection requiring an operation is rare. In our case, antibiotics were not effective in treating the abscess therefore surgery was required. An early diagnosis using serological studies, ultrasound of the abdomen, and fecal culture, with appropriate administration of antibiotics, may have avoided the need for surgery. Considering YP infection as a differential diagnosis is therefore important when encountering patients with enterocolitis, especially with right lower quadrant pain. Early diagnosis may assist in avoiding unnecessary operations.

Conclusion

Diagnosis of YP infection may be missed or delayed because it is rare and difficult to detect, and must be distinguished from appendicitis. Although most YP infections are self-limiting, some rare cases will require surgery, therefore early diagnosis is essential.

Salmonella, Shigella, and yersinia

Salmonella, Shigella, and Yersinia cause a well-characterized spectrum of disease in humans, ranging from asymptomatic carriage to hemorrhagic colitis and fatal typhoidal fever. These pathogens are responsible for millions of cases of food-borne illness in the United States each year, with substantial costs measured in hospitalizations and lost productivity. In the developing world, illness caused by these pathogens is not only more prevalent but also associated with a greater case-fatality rate. Classic methods for identification rely on selective media and serology, but newer methods based on mass spectrometry and polymerase chain reaction show great promise for routine clinical testing.

Immunization with a DNA adenine methylase over-producing Yersinia pseudotuberculosis vaccine confers robust cross-protection against heterologous pathogenic serotypes

Yersinia pseudotuberculosis is a foodborne pathogen that can cause serious human illness. Although the source and route of transmission often remain obscure, livestock have been implicated in some cases. The diversity of yersiniae present on farms and their widespread distribution in animal and environmental reservoirs necessitates the use of broad prophylactic strategies that are efficacious against many serotypes simultaneously. Herein, immunization of mice with a modified, live attenuated Y. pseudotuberculosis vaccine that overproduces the DNA adenine methylase (Dam(OP)) conferred robust protection against virulent challenge (150-fold LD50) with homologous and heterologous serotypes that have been associated with human disease (O:1, O:1a, O:3). Further, the dam gene was shown to be essential for cell viability in all (7 of 7) Y. pseudotuberculosis strains tested. Direct selection for the inheritance of dam mutant alleles in Y. pseudotuberculosis resulted in dam strain variants that contained compensatory (second-site suppressor) mutations in genes encoding methyl-directed mismatch repair proteins (mutHLS) that are involved in suppression of the non-viable cell phenotype in all (19/19) strains tested. Such dam mutH variants exhibited a significant increase in virulence and spontaneous mutation frequency relative to that of a Dam(OP) vaccine strain. These studies indicate that Y. pseudotuberculosis Dam(OP) strains conferred potent cross-protective efficacy as well as decreased virulence and spontaneous mutation frequency relative to those that lack Dam, which have compensatory mutations in mutHLS loci. These data suggest that development of yersiniae livestock vaccines based on Dam overproduction is a viable mitigation strategy to reduce these potential foodborne contaminants.

High frequency of reactive arthritis in adults after Yersinia pseudotuberculosis O:1 outbreak caused by contaminated grated carrots

OBJECTIVE

We describe the epidemiological and microbiological process in the clearing of a foodborne outbreak of Yersinia pseudotuberculosis O:1 linked to raw carrots and frequency of the associated reactive extra-gastrointestinal manifestations.

METHODS

The patient samples were investigated by routine culture or antibody testing methods. The real-time bacterial PCR was used to detect Y pseudotuberculosis in samples from the grated carrots and in those taken from the carrot storage. Genotype of bacterial isolates was determined by pulsed-field gel electrophoresis. For case identification, we retrospectively looked over the laboratory files of the central hospital focusing on the time period of the outbreak.

RESULTS

Altogether 49 case patients were identified. Y pseudotuberculosis was detected by real-time PCR analysis in samples taken from grated carrots and from the carrot distributor. Bacterial isolates originating from the farm environment showed identical serotype (O:1) and genotype (S12) with the patients' isolates. Among 37 adults, reactive arthritis (ReA) was found in 8 (22%) and three adults had probable ReA. Six (67%) out of nine human leucocyte antigen (HLA) typed patients with ReA were HLA-B27 positive. Erythema nodosum was found in 42% of the 12 children, whereas none of them had definite ReA.

CONCLUSIONS

In this outbreak, Y pseudotuberculosis was for the first time detected in both patient and food samples. ReA was more common than earlier reported in the outbreaks associated with this pathogen; the reason may be that the previous outbreaks have occurred among children. HLA-B27 frequency was higher than usually reported in single-source outbreaks of ReA.

Pathogenesis of Y. enterocolitica and Y. pseudotuberculosis in Human Yersiniosis

Yersiniosis is a food-borne illness that has become more prevalent in recent years due to human transmission via the fecal-oral route and prevalence in farm animals. Yersiniosis is primarily caused by Yersinia enterocolitica and less frequently by Yersinia pseudotuberculosis. Infection is usually characterized by a self-limiting acute infection beginning in the intestine and spreading to the mesenteric lymph nodes. However, more serious infections and chronic conditions can also occur, particularly in immunocompromised individuals. Y. enterocolitica and Y. pseudotuberculosis are both heterogeneous organisms that vary considerably in their degrees of pathogenicity, although some generalizations can be ascribed to pathogenic variants. Adhesion molecules and a type III secretion system are critical for the establishment and progression of infection. Additionally, host innate and adaptive immune responses are both required for yersiniae clearance. Despite the ubiquity of enteric Yersinia species and their association as important causes of food poisoning world-wide, few national enteric pathogen surveillance programs include the yersiniae as notifiable pathogens. Moreover, no standard exists whereby identification and reporting systems can be effectively compared and global trends developed. This review discusses yersinial virulence factors, mechanisms of infection, and host responses in addition to the current state of surveillance, detection, and prevention of yersiniosis.

Reactive arthritis

Reactive arthritis (ReA) can be defined as the development of sterile inflammatory arthritis as a sequel to remote infection, often in the gastrointestinal or urogenital tract. Although no generally agreed-upon diagnostic criteria exist, the diagnosis is mainly clinical, and based on acute oligoarticular arthritis of larger joints developing within 2-4 weeks of the preceding infection. According to population-based studies, the annual incidence of ReA is 0.6-27/100,000. In addition to the typical clinical picture, the diagnosis of ReA relies on the diagnosis of the triggering infection. Human leucocyte antigen (HLA)-B27 should not be used as a diagnostic tool for a diagnosis of acute ReA. In the case of established ReA, prolonged treatment of Chlamydia-induced ReA may be of benefit, not only in the case of acute ReA but also in those with chronic ReA or spondylarthropathy with evidence of persisting chlamydia antigens in the body. In other forms of ReA, there is no confirmed evidence in favour of antibiotic therapy to shorten the duration of acute arthritis. The outcome and prognosis of ReA are best known for enteric ReA, whereas studies dealing with the long-term outcome of ReA attributable to Chlamydia trachomatis are lacking.

Attenuation and preserved immunogenic potential of Yersinia pseudotuberculosis mutant strains evidenced in oral pig model

Experimental oral infection of pigs with a parental Yersinia pseudotuberculosis strain pIB102, serotype O:3 and two mutant isogenic strains - pIB155,DeltayopK and pIB44,DeltaypkA has been carried out. Clinical findings, microbiological and immunological parameters were examined in dynamics from day 7 to day 60 post-infection (p.i.). All types of infections ran asymptomatically, without hyperthermia, loss of appetite, etc. Experiments on the blood parameters demonstrated a transient leucocytosis with lymphocytosis and monocytosis better expressed after yopK infection. Even though pig is usually known as a reservoir of yersiniae, bacterial colonization was found in mesenterial lymph nodes and tonsils on day 7, respectively 14 p.i. with parental strain, and only in tonsils on day 14 p.i. with both mutant strains. The augmented sensitivity of mutants to the bactericidal effect of leukocytes and blood sera is the characteristic feature of attenuation in their pathogenicity, compared to the parental strain. Comparative in vitro experiments on the immune response and immunostimulating capacity of Y. pseudotuberculosis mutant strains verify their preserved immunogenic potential, predominantly in case of yopK. Hyperplasia and strong activation of the lymph tissue of Peyer's patches, mesenterial lymph nodes, tonsils and spleen of pigs challenged with both mutant strains were proved as immunomorphological rearrangements. The results obtained give the reason to claim that the genetically constructed yopK null mutant strain is significantly attenuated but is still immunogenic and has the potential for a live vaccine carrier strain.

Transmission of Yersinia pseudotuberculosis in the pork production chain from farm to slaughterhouse

The transmission of Yersinia pseudotuberculosis in the pork production chain was followed from farm to slaughterhouse by studying the same 364 pigs from different production systems at farm and slaughterhouse levels. In all, 1,785 samples were collected, and the isolated Y. pseudotuberculosis strains were analyzed by pulsed-field gel electrophoresis. The results of microbial sampling were combined with data from an on-farm observation and questionnaire study to elucidate the associations between farm factors and the prevalence of Y. pseudotuberculosis. Following the same pigs in the production chain from farm to slaughterhouse, we were able to show similar Y. pseudotuberculosis genotypes in live animals, pluck sets (containing tongue, tonsils, esophagus, trachea, heart, lungs, diaphragm, liver, and kidneys), and carcasses and to conclude that Y. pseudotuberculosis contamination originates from the farms, is transported to slaughterhouses with pigs, and transfers to pluck sets and carcasses in the slaughter process. The study also showed that the high prevalence of Y. pseudotuberculosis in live pigs predisposes carcasses and pluck sets to contamination. When production types and capacities were compared, the prevalence of Y. pseudotuberculosis was higher in organic production than in conventional production and on conventional farms with high rather than low production capacity. We were also able to associate specific farm factors with the prevalence of Y. pseudotuberculosis by using a questionnaire and on-farm observations. On farms, contact with pest animals and the outside environment and a rise in the number of pigs on the farm appear to increase the prevalence of Y. pseudotuberculosis.

[Three cases of Yersinia pseudotuberculosis gastrointestinal infection having no apparent epidemiological relationship, caused by identical strains]

INTRODUCTION

Gastrointestinal infections caused by Yersinia pseudotuberculosis are uncommon in our country and the epidemiology of the infection is uncertain.

METHODS

We describe three cases of Y. pseudotuberculosis gastrointestinal infection, all detected within one month of time. A possible epidemiological relationship among these cases, as well as the microbial characteristics of the isolates, was investigated. RESULTS. No epidemiological relationships were found among the three cases. Nevertheless, all three isolates were identical according to phenotyping and molecular marker studies.

CONCLUSION

This report discusses the possible source of infection in these cases, with reference to published data from sporadic cases and outbreaks of infection by this microorganism. We suggest that future studies are needed to know the real incidence of Y. pseudotuberculosis in our country.

A palpable right lower abdominal mass due to Yersinia mesenteric lymphadenitis

Infection by Yersinia pseudotuberculosis has become of increasing pathological importance. This report describes the case of a 12-year-old female with mesenteric lymphadenitis due to Yersinia pseudotuberculosis. The patient presented with fever, abdominal pain, and a palpable right abdominal mass. Abdominal ultrasonic imaging and computerized axial tomography (CT) revealed a mass. An exploratory laparotomy was performed, followed by appendectomy and mesenteric lymph node biopsy. The diagnosis of Yersinia infection was confirmed by serology and bacterial culture of the biopsy material. This condition should be considered in patients with a right lower abdominal mass and symptoms similar to those of appendicitis.

Reactive arthritis after an outbreak of Yersinia pseudotuberculosis serotype O:3 infection

OBJECTIVE

To determine the occurrence and clinical characteristics of reactive arthritis (ReA) after an outbreak of Yersinia pseudotuberculosis serotype O:3 infection.

METHODS

From 15 October to 6 November 1998, a widespread outbreak of Y pseudotuberculosis serotype O:3 occurred in Finland. A questionnaire on musculoskeletal symptoms was mailed to 38 patients with infection confirmed by culture. All patients who reported joint symptoms were interviewed by phone and their medical records of outpatient visits or hospital admission because of recent joint symptoms were reviewed.

RESULTS

Thirty three of 38 (87%) patients returned the questionnaire. Reactive musculoskeletal symptoms were reported by 5/33 (15%): four patients (12%) fulfilled the criteria for ReA and one additional patient had reactive enthesopathy. The patients with ReA were adults (age range 40-47 years), whereas the patient with reactive enthesopathy was a 14 year old boy. In all patients with ReA, the arthritis was polyarticular. In addition to peripheral arthritis, other musculoskeletal symptoms included sacroiliitis (one patient), pain in Achilles tendon (one patient), and heel pain (two patients). HLA-B27 was positive in all the three patients tested. In three of four patients with ReA, the duration of acute arthritis was over six months.

CONCLUSION

Y pseudotuberculosis serotype O:3 infection is frequently associated with ReA and the clinical picture is severe.

Microbial factors in spondyloarthropathies: insights from population studies

Infections and genetics play a role in the development of reactive arthritis. The clinical manifestations and severity of the features depend on the triggering infections and the epidemiologic setting. Reports from hospital-based series show the lowest frequency of reactive arthritis, but often, patients have severe arthritis associated with a high frequency of HLA-B27. At the population level, reactive arthritis occur in 7 to 15% of the infected subjects. The disease is usually mild, affects small joints, can be polyarticular, often rapidly disappears, and has a low association with HLA-B27. There also seems to be a change in the spectrum of triggering infections. Reports of Yersinia arthritis are less common, whereas arthritis in association with Campylobacter or Salmonella infections seems to be increasing. The role of early antimicrobial chemotherapy for the prevention of reactive arthritis needs to be studied.

The superantigen gene ypm is located in an unstable chromosomal locus of Yersinia pseudotuberculosis

Yersinia pseudotuberculosis produces YPM (Y. pseudotuberculosis-derived mitogen), a superantigenic toxin that exacerbates the virulence of the bacterium in vivo. To date, three alleles of the superantigen gene (ypmA, ypmB, and ypmC) have been described. These genes are not found in all Y. pseudotuberculosis strains and have a low GC content, suggesting their location on mobile genetic elements. To elucidate this question, the genetic environment of the superantigen-encoding genes was characterized and 11 open reading frames (ORFs) were defined. Sequence analysis revealed that the ypm genes were not associated with plasmids, phages, transposons, or pathogenicity islands and that the superantigen genes were always located in the chromosome between ORF3 and ORF4. Nonsuperantigenic strains exhibited the same genetic organization of the locus but lacked the ypm gene between ORF3 and ORF4. A new insertion sequence, designated IS1398, which displays features of the Tn3 family, was characterized downstream of the ypmA and ypmC genes. A 13.3-kb region containing the ypm genes was not found in the genome of Y. pestis (CO92 and KIM 5 strains). We experimentally induced deletion of the ypm gene from a superantigen-expressing Y. pseudotuberculosis: using the association of aph(3')-IIIa and sacB genes, we demonstrated that when these reporter genes were present in the ypm locus, deletion of these genes was about 250 times more frequent than when they were located in another region of the Y. pseudotuberculosis chromosome. These results indicate that unlike other superantigenic toxin genes, the Yersinia ypm genes are not associated with mobile genetic elements but are inserted in an unstable locus of the genome.

Yersinia pseudotuberculosis with limited genetic diversity is a common finding in tonsils of fattening pigs

A total of 425 pig tonsils, including 210 tonsils from fattening pigs and 215 from sows, from seven different abattoirs in Finland were studied for the occurrence of Yersinia pseudotuberculosis from 1999 to 2000. The mean prevalence of Y. pseudotuberculosis in fattening pig tonsils was 4%, varying from 0 to 10% between slaughterhouses. Y. pseudotuberculosis was not recovered from sow tonsils. All 30 Y. pseudotuberculosis isolates from eight pig tonsils were recovered after cold enrichment. Seventeen isolates from seven tonsils were found after cold enrichment for 14 days, followed by alkali treatment. Y. pseudotuberculosis was not isolated after direct plating, overnight enrichment, or selective enrichment. All 30 isolates belonged to bioserotype 2/0:3 and carried the virF gene in the virulence plasmid. The isolates exhibited calcium dependence and Congo red absorption. The pyrazinamidase test gave variable results. All isolates were characterized with pulsed-field gel electrophoresis (PFGE). Using SpeI, NotI, and XbaI enzymes, seven, five, and two different PFGE patterns were obtained, respectively. A total of 11 genotypes, gI to gXI, identified by a combination of the various SpeI, NotI, and XbaI profiles, were detected. Three pigs were found to carry more than one genotype. Overall, variations between PFGE patterns were small, indicating genetic homogeneity among pig strains of bioserotype 2/0:3.

Clinical and microbiological follow-up of an outbreak of Yersinia pseudotuberculosis serotype Ib

Yersinia pseudotuberculosis, a food-borne pathogen, causes infection that commonly presents as gastroenteritis and mesenteric lymphadenitis. Post-infectious complications include erythema nodosum, reactive arthritis and, less commonly, uveitis and nephritis. Six serotypes of Y. pseudotuberculosis have been identified, and post-infectious complications have been identified following infection with some, but not all, serotypes. The first recognized outbreak of Y. pseudotuberculosis serotype lb occurred in British Columbia in November 1998. We documented the incidence of post-infectious complications and the effect of antibiotic use on the clinical course. Four months after the outbreak, a standardized questionnaire asking about symptoms and antibiotic use was administered by telephone to laboratory-confirmed cases. Stool samples were collected to examine for chronic carriage of Y. pseudotuberculosis and 59 of 74 eligible cases participated. The most common post-infectious symptoms were rash (8/59) and joint pain (7/59). Microbiological analysis, at follow-up, revealed 0/36 stools positive for Y. pseudotuberculosis. Seventy-eight percent of cases had taken antibiotics during their acute illness. There was no significant difference in the frequency of post-infectious symptoms between cases who had or had not taken antibiotics. The post-infectious pathogenicity of Y. pseudotuberculosis serotype lb is lower than that documented for other serotypes. Antibiotic use did not significantly alter the reported clinical course of illness.

The superantigenic toxin of Yersinia pseudotuberculosis: a novel virulence factor?

Recently, a superantigenic toxin designated YPM (Yersinia pseudotuberculosis-derived mitogen) was characterized in the supernatant of Y. pseudotuberculosis, a Gram-negative bacterium involved in human enteric infection. To assess the role of YPM in pathophysiology of Y. pseudotuberculosis, a superantigen-deficient mutant was constructed and its virulence was tested in a murine model of infection and compared with the virulence of the wild-type strain (wt). Determination of the survival rate after intravenous inoculation of mice clearly demonstrated a higher survival rate when animals were infected with the superantigen-deficient strain. This decreased virulence of the mutant strain could not be explained by a lower bacterial growth rate in spleen, liver or lung of infected animals. Therefore, production of IFNgamma, TNFalpha, IL-2, IL-6 and IL-10 was followed during the course of infection by cytokine assay in the blood and mRNA detection in the spleen. IL-6 and IFNgamma were the two major cytokines detected whereas TNFalpha production was never observed.

Superantigen YPMa exacerbates the virulence of Yersinia pseudotuberculosis in mice

Yersinia pseudotuberculosis, a gram-negative bacterium responsible for enteric and systemic infection in humans, produces a superantigenic toxin designated YPMa (Y. pseudotuberculosis-derived mitogen). To assess the role of YPMa in the pathogenesis of Y. pseudotuberculosis, we constructed a superantigen-deficient mutant and compared its virulence in a mouse model of infection to the virulence of the wild-type strain. Determination of the survival rate after intravenous (i.v.) bacterial inoculation of OF1 mice clearly showed that inactivation of ypmA, encoding YPMa, reduced the virulence of Y. pseudotuberculosis. Mice infected i.v. with 10(4) and 10(5) wild-type bacteria died within 9 days, whereas mice infected with the ypmA mutant survived 12 and 3 days longer, respectively. This decreased virulence of the ypmA mutant strain was not due to an impaired colonization of the spleen, liver, or lungs. In contrast to i.v. challenge, bacterial inoculation by the intragastric (i.g.) route did not reveal any difference in virulence between wild-type Y. pseudotuberculosis and the ypmA mutant since the 50% lethal doses were identical for both strains. Moreover, inactivation of ypmA gene did not affect the bacterial growth of Y. pseudotuberculosis in Peyer's patches, mesenteric lymph nodes (MLNs), and spleen after oral infection. Histological studies of spleen, liver, lungs, heart, Peyer's patches, and MLNs after i.v. or i.g. challenge with the wild type or the ypmA mutant did not reveal any feature that can be specifically related to YPMa. Our data show that the superantigenic toxin YPMa contributes to the virulence of Y. pseudotuberculosis in systemic infection in mice.

Report of four cases of Yersinia pseudotuberculosis septicemia and a literature review

Yersinia pseudotuberculosis is a rare cause of disease in humans, the most common manifestation being mesenteric lymphadenitis accompanied by abdominal pain and fever. A septicemic form of Yersinia pseudotuberculosis infection has been reported only rarely. It is usually seen in patients with underlying disorders such as diabetes, hepatic cirrhosis or iron overload. Fifty-four cases of septicemic infection were found in the literature. The earlier published cases are reviewed, and four cases occurring in Finland during the period February to June 1992 are reported.

Acute tubulointerstitial nephritis in association with Yersinia pseudotuberculosis infection

A 4-year-old girl was diagnosed as having acute renal failure due to tubulointerstitial nephritis. The girl presented with remittent fever, vomiting and non-oliguric acute renal failure with sterile pyuria and tubular reabsorptive dysfunction. Ultrasound examination revealed that the kidneys were markedly enlarged with diffuse hyperechogenicity in the cortex when the abnormal renal function was present and were restored in size and echogenicity when the renal function normalised. A diagnosis of Yersinia pseudotuberculosis infection was based on a rise in haemagglutination titres against the organism.

A right lower abdominal mass due to Yersinia mesenteric lymphadenitis

We report the case of a 14-year-old female with Yersinia mesenteric lymphadenitis presenting as a right lower abdominal mass. Although such cases are very rare, Yersinia infection should be considered in the differential diagnosis of a right lower abdominal mass.

Risk of Yersinia infection among butchers

The purpose of this study was to evaluate the risk of yersinia infection among butchers. Serum samples were collected from 146 abattoir workers, stratified into 3 groups according to exposure to swine throats and intestines. 100 healthy blood donors were used as controls. Antibodies against Yersinia enterocolitica O:3 and O:9 and Y. pseudotuberculosis I and III were measured using ELISA. Symptoms associated with yersiniosis were recorded in a questionnaire. Antibodies against Y. enterocolitica O:3 were observed more often in the sera of abattoir workers (19%), especially in butchers handling swine throats and intestines (27%), than in the sera of healthy blood donors (10%). During the 6 months preceding this study, 30-40% of the workers reported symptoms of abdominal pains and diarrhoea. However, the symptoms did not correlate with the occurrence of antibodies. One butcher had developed a yersinia-triggered prolonged reactive arthritis. Tonsil samples were collected from 120 pigs to determine the extent of yersinia contamination. Positive isolates were obtained from 54 pigs (45%). Y. enterocolitica O:3 was isolated from 31 pigs and Y. pseudotuberculosis III from 11 pigs. All of these strains shared characteristics typical for virulent strains. We conclude that yersinia infections are an occupational health risk to workers slaughtering swine in the abattoirs.