Monday, 25 December 2017

Yersinia enterocolitica: Diarrhoea causative agent

Yersinia enterocolitica is a Gram negative rod-shaped bacterium in the family of Enterobacteriaceae known as causative agent of gastrointestinal infections and most often causes the disease yersiniosis with a variety of symptoms such as enterocolitis, acute diarrhea, terminal ileitis and pseudoappendicitis but, if it spreads systemically, can also result in fatal sepsis. The genus Yersinia includes 11 species: Y. pestis, Y. pseudotuberculosis, Y. enterocolitica, Y. frederiksenii, Y. intermedia, Y. kristensenii, Y. bercovieri, Y. mollaretii, Y. rohdei, Y. aldovae, and Y. ruckeri. Among them, only Y. pestis, Y. pseudotuberculosis, and certain strains of Y. enterocolitica are of pathogenic importance for humans and certain warm-blooded animals, whereas the other species are of environmental origin and may, at best, act as opportunists. However, Yersinia strains can be isolated from clinical materials, so have to be identified at the species level.
Signs and symptoms
Symptoms of Y. enterocolitica infection typically include Diarrhea which is the most common clinical manifestation of this infection; diarrhea may be bloody in severe cases, low grade fever, abdominal pain, vomiting. The patient may also develop erythema nodosum, which manifests as painful, raised red or purple lesions, mainly on the patient’s legs and trunk. Lesions appear 2-20 days after the onset of fever and abdominal pain and resolve spontaneously in most cases in about a month.
Y. enterocolitica infection can be diagnosis by a number of methods which includes Stool culture - This is the best way to confirm a diagnosis of Y. enterocolitica. The figure above shows the growth of Y. enterocolitica on CIN (Cefsulodin, Irgasan, Novobiocin) Agar. The characteristic deep red center with a transparent margin, or "bull's-eye" appearance of Yersinia andAeromonas colonies is important for identification, and is due to the presence of mannitol. Y. enterocolitica ferments the mannitol in the medium, producing an acid pH which gives the colonies their red color and the "bull's eye" appearance. Sodium deoxycholate, cefsulodin, irgasan, and novobiocin are added as selective agents. Altorfer found that by reducing the concentration of cefsulodin from 15.0 to 4.0mcg/ml, CIN Agar could also be used to selectively isolate Aeromonas spp., in addition to Yersinia.
Other diagnosis methods include tube agglutination, Enzyme-linked immunosorbent assays
Radioimmunoassays, Imaging studies - Ultrasonography or computed tomography (CT) scanning may be useful in delineating true appendicitis from pseudoappendicitis, Colonoscopy - Findings may vary and are relatively nonspecific, Joint aspiration in cases of Yersinia- associated reactive arthropathy
Care in patients with Y enterocolitica infection is primarily supportive, with good nutrition and hydration being mainstays of treatment
First-line drugs used against the bacterium include the following agents:
Third-generation cephalosporins
Trimethoprim-sulfamethoxazole (TMP-SMZ)
Fluoroquinolones - not approved for use in children under 18 years