Yersinia species are facultative anaerobic gram-negative coccobacilli. The most common species that cause yersiniosis are Yersinia enterocolitica (serogroups O:3, O:5,27, O:8, and O:9), but disease is also caused by Y. pseudotuberculosis. Yersinia pestis, the causative agent of plague, is discussed in this chapter under the heading Plague (Bubonic, Pneumonic, Septicemic).
Transmission of Yersinia spp. may occur as a result of consuming or handling contaminated food (commonly raw or undercooked pork products, such as chitterlings); consuming milk that was not pasteurized, inadequately pasteurized, or contaminated after pasteurization; or being exposed to untreated water. Yersinia spp. may also be transmitted by direct or indirect contact with animals. Pigs are a major reservoir of pathogenic Y. enterocolitica, but a variety of other farm, wild, and domestic animals, such as cattle, deer, and dogs may harbor Yersinia spp. Transmission through blood product transfusions has been reported.
Yersiniosis is most commonly reported from northern Europe (particularly Scandinavia), Japan, and Canada; however, it is not a reportable condition in most countries, so infections in countries without surveillance programs may be underrepresented; it is not nationally reportable in the United States. In the United States, Y. enterocolitica causes about 92% of infections with known species information, accounting for an estimated 117,000 illnesses, 640 hospitalizations, and 35 deaths every year.
In temperate climates, the risk of infection is higher in cooler months. Children are infected more often than adults. People with diseases that cause high iron levels, such as hemochromatosis and thalassemia, including those on iron chelation treatment, are at higher risk for infection and severe disease. The incidence among travelers to developing countries is generally low. A US study found that approximately 6% of Y. enterocolitica infections were travel associated.
The incubation period is 4–6 days (range, 1–14 days), and symptom onset may be more gradual compared with infections caused by other enteric pathogens. Enterocolitis is the most common clinical presentation; symptoms typically include fever, abdominal pain, and diarrhea, which may be bloody and can persist for several weeks. Sore throat may also occur, particularly in children. Mesenteric adenitis, which presents as pain mimicking appendicitis, has been well described. Necrotizing enterocolitis has been described in young infants. Reactive arthritis affecting the wrists, knees, and ankles can occur, usually 1 month after the initial diarrhea episode, resolving after 1–6 months. Erythema nodosum, manifesting as painful, raised red or purple lesions along the trunk and legs, can occur and usually resolves spontaneously within 1 month.
Diagnosis is frequently made by isolating the organism from stool, blood, bile, wound, throat swab, mesenteric lymph node, cerebrospinal fluid, or peritoneal fluid. If yersiniosis is suspected, the clinical laboratory should be notified because cold enrichment, alkali treatment, or plating on CIN agar can be used to increase the likelihood of a positive culture. Several culture-independent diagnostic tests (CIDTs) are now available and have more than doubled the detection rate of Yersinia spp. in the United States. CIDT panels typically target only Y. enterocolitica, and the rarity of yersiniosis has precluded robust evaluation of the specificity and sensitivity of CIDT platforms through prospective studies. Culture is required to determine species and for antibiotic susceptibility testing.
Most infections are self-limited. Antibiotics should be given for moderate to severe cases. Y. enterocolitica isolates are usually susceptible to trimethoprim-sulfamethoxazole, aminoglycosides, third-generation cephalosporins, fluoroquinolones, and tetracyclines; they are typically resistant to first-generation cephalosporins and most penicillins. Antimicrobial therapy has no effect on postinfectious sequelae.
Travelers can reduce the risk of Yersinia spp. infection by avoiding consumption of raw or undercooked pork products, unpasteurized milk products, and untreated water (see Chapter 2, Food & Water Precautions). Washing hands with soap and water before eating and preparing food, after contact with animals, and after handling raw meat helps reduce risk.
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