Yersinia enterocolitica: Pathogenesis and Clinical Findings, Diagnostic Laboratory Tests, Treatment, Prevention and Control.

Question 1

Yersinia enterocolitica: pathogenesis

Answer 1

1. Yersinia enterocolitica is transmitted mainly via ingestion of contaminated food (especially pork), water, or contact with infected animals.
2. it invades M cells of the intestinal mucosa, particularly in the ileum and Peyer’s patches.
3. It uses adhesins (invasin, YadA) and a type III secretion system (T3SS) to inject Yersinia outer proteins (Yops) into host cells, which block phagocytosis and immune responses.
4. It multiplies in mesenteric lymph nodes, causing inflammation and necrosis.
5. It can mimic appendicitis and may trigger autoimmune conditions like reactive arthritis.

Question 2

Yersinia enterocolitica: clinical findings

Answer 2

1. Y. enterocolitica commonly causes enterocolitis, especially in children.
2. Symptoms include fever, abdominal pain (often in the right lower quadrant), and diarrhea that may be bloody.
3. In adults, it can mimic acute appendicitis (pseudoappendicitis).
4. In some cases, it leads to mesenteric lymphadenitis.
5. Post-infectious complications may include erythema nodosum and reactive arthritis, particularly in HLA-B27–positive individuals.
6. Sepsis and extraintestinal infections (e.g., osteomyelitis) can occur in immunocompromised patients or those with iron overload (e.g., thalassemia).

Question 3

Yersinia enterocolitica: diagnostic laboratory tests

Answer 3

Diagnosis is by culture of stool, blood, or lymph node aspirates. Cold enrichment (incubation at 4°C for 1–3 weeks) enhances recovery from stools. It grows on standard media but is best isolated using selective media like cefsulodin-irgasan-novobiocin (CIN) agar, which produces red ‘bull’s-eye’ colonies. Serologic tests and PCR can aid diagnosis. WBCs may be elevated in blood tests.

Question 4

Yersinia enterocolitica: treatment

Answer 4

In most cases, infection is self-limiting and does not require antibiotics. For severe or systemic infections, effective antibiotics include doxycycline with an aminoglycoside, fluoroquinolones, or trimethoprim-sulfamethoxazole. Iron-overloaded patients may be more susceptible and require more aggressive treatment.

Question 5

Yersinia enterocolitica: prevention and control

Answer 5

Preventive measures include proper cooking of pork and other meats, pasteurization of milk, and good hygiene practices, especially in food handling. Avoiding consumption of raw or undercooked chitterlings (pig intestines) is particularly important. Infections must be reported in some countries, and outbreaks require public health investigation.