Approach Considerations
Testing should be done for Yersinia enterocolitica in people with persistent abdominal pain (especially school-aged children with right lower quadrant pain mimicking appendicitis who may have mesenteric adenitis), and in people with fever at epidemiologic risk for yersiniosis, including infants with direct or indirect exposures to raw or undercooked pork products.
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If Yersinia infection is suspected, the clinical laboratory should be notified and instructed to culture on cefsulodin-irgasan-novobiocin (CIN) or other specific media for growing it at 25 degrees celsius. Y enterocolitica is non-lactose fermenting, oxidase negative, and urease positive.
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Diagnosis is made by isolating the organism from stool, blood, bile, wound, throat swab, mesenteric lymph node, cerebrospinal fluid, or peritoneal fluid.
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GI panel multiplex PCR can be used for diagnositic purposes. Yersinia is included as a target on 3 commercial, FDA-cleared, multiplex assays for the detection of gastrointestinal pathogens, ie, Verigene EP, FilmArray GI, and xTAG GPP. [4]
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Clinical consideration should be included in the interpretation of results of multiple-pathogen nucleic acid amplification tests because these assays detect DNA and not necessarily viable organisms.
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Imaging studies - Ultrasonography or computed tomography (CT) scanning may be useful in delineating true appendicitis from pseudoappendicitis.
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Colonoscopy - Findings may vary and are relatively nonspecific.
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In case of Yersinia- associated post infectious reactive arthropathy, joint aspirate would be culture negative. However, Yersinia rarely may also cause pyogenic osteoarthrits or osteomyelitis in acute invasive settings with hematogenous spread.
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Enzyme-linked immunosorbent assays and radioimmunoassays for antibodies detection. Patients who developed reactive arthritis tended to maintain Ig A and Ig G anti Yersinia antibodies. [52]
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Stool Culture
Stool samples tested for leukocytes usually produce positive results, but Y enterocolitica is difficult to distinguish from other invasive pathogens. Stool samples from infected patients should be handled carefully to avoid infecting others.
When Y enterocolitica infection is suspected, instruct the microbiology laboratory to use cefsulodin-Irgasan-novobiocin (CIN) agar, which is a differential selective medium with increased yield for Y enterocolitica. It requires 18-20 hours of incubation at 25°C to create unique colony morphology, representing 0.5- to 1-mm colonies with a red "bull's-eye" and a clear border. Use of this media allows differentiation between Y enterocolitica and Y enterocolitica– like isolates.
When using conventional enteric media, MacConkey agar incubated at 25°C for 48 hours produces the best results. [53]
Recovery of organisms from otherwise sterile samples, such as blood, cerebrospinal fluid (CSF), and lymph node tissue, usually is faster than recovery from stool samples. Isolation of Y enterocolitica from stool is hampered by slow growth and overgrowth of normal flora.
Serodiagnosis
Serodiagnosis is possible with various methods, including tube agglutination, enzyme-linked immunosorbent assays, and radioimmunoassays. However, carefully interpret the serotest results for Y enterocolitica infection if a positive stool culture result is absent. Cross-reactions with other organisms can occur—including with Brucella, Morganella, and Salmonella —and a background seroprevalence rate among different populations may confound the diagnosis by acting as a false-positive result.
Agglutinin titers typically increase 1-2 weeks after infection and peak at 1:200. However, elevated levels can be found for years after infection, which also limits the usefulness of serodiagnosis.
DNA Microarray
Advanced experimental techniques for diagnosis of Y enterocolitica infection include polymerase chain reaction (PCR) assay, immunohistochemical staining, and DNA microarray. Diagnostic DNA microarray for pathogenetic organisms is a technique that is used to identify multiple genes from different kinds of pathogens, allowing it to be used to detect different species, biotypes, and/or toxins of pathogenic organisms in the same specimens. This is the major advantage over the conventional PCR assay technique, which is used to identify only 1 gene from a hybridization. DNA microarray also is more sensitive and accurate than the multiplex PCR. [54]
Colonoscopy
Typically, in patients with Y enterocolitica infection, the cecum contains aphthoid lesions and the terminal ileum has small, round elevations and ulcers (as seen in the image below). An exudate may be present. The left side of the colon typically is unaffected, but case reports have described left-sided colitis with serotype O:8.
Yersinia enterocolitis in a 45-year-old white woman who presented with chronic diarrhea.
Histologic Findings
Histologic findings in Y enterocolitica infection are consistent with acute and chronic inflammation. Yersiniosis does not produce unique histologic findings. Epithelial cell granulomas with suppuration of the centers of the granulomas (central microabscesses) have been reported. These granulomas were composed of numerous histiocytes with or without epithelioid cell features, along with scattered small T-lymphocytes and plasmacytoid monocytes. [55]
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Yersinia enterocolitis in a 45-year-old white woman who presented with chronic diarrhea.
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Gram stain of Yersinia enterocolitica.
