Yersiniosis is caused by Yersinia enterocolitica and Y.
pseudotuberculosis (Y. pestis causes human plague).
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Causative
organism: Y.
enterocolitica and Y. pseudotuberculosis are gram-negative , oval
coccoid or rod-shape bacteria.
Yersinia
enterocolitica is an important food-borne pathogen.
Both
species are motile, facultative anaerobes found in the faeces of wild
and domestic animals, including rodents, sheep, cattle, dogs, cats,
and horses. Birds such as turkeys, ducks, geese, pigeons and canaries
are common sources of Y. pseudotuberculosis.
Both
organisms have been isolated from drinking water and milk. Y.
enterocolitia is more likely to be acquired from contaminated meat and
Y. pseudotuberculosis from contact with infected animals.
Using PCR, the
detection rate of pathogenic Y. enterocolitica in raw pork products is
high, which reinforces the assumption that these products are a
transmission link between pigs and humans.
Y. enterocolitica
may be associated with the development of inflammatory bowel disease.
Yersinia
enterocolitica and Y. pseudotuberculosis have been
implicated as causes of appendicitis, ileocolitis, and mesenteric
adenitis.
Pathology
and pathogenesis:
Ingested Y. enterocolitica proliferates
in the ileum, invades the mucosa, produces ulcerations and necrosis of
Peyer’s patches, and migrates by way of the lymphatics to the
mesenteric lymph nodes.
Arthralgia, arthritis, and erythema
nodosum are complications.
Septicemia is an uncommon complication
but kills about one-half of those affected.
Fever, diarrhea (sometimes bloody) and
abdominal pain begin 4 to 10 days after penetration of the mucosa.
Ingested Y. pseudotuberculosis
penetrates the ileal mucosa, localizes in ileocaecal lymph nodes, and
produces abscesses and granulomas in the lymph nodes, spleen, and
liver.
The granulomas may be centered in the
lymphoid follicles.
Diarrhea and abdominal pain in the
right lower quadrant with fever may lead to an erroneous diagnosis of
appendicitis.
Diagnosis:
No histologic
features distinguish reliably between Yersinia species, or between
Yersinia-positive and Yersinia-negative cases. Because special stains
and cultures are often not diagnostic, PCR analysis is an excellent
technique for the diagnosis of Yersinia.
Treatment: Streptomycin, gentamycin, tetracycline
and trimethoprim-sulfamethoxazole are the antibiotics of choice.
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