Yersinia Enterocolitica Infection

Yersinia enterocolitica is a Gram-negative coccobacillus that causes enterocolitis, terminal ileitis, mesenteric adenitis and, rarely, septicaemia.

• Source is pork (particularly raw or undercooked), unpasteurised milk, contaminated water and transfusion of stored blood (it grows at 4 C).
• It affects children and young adults most commonly; iron overload, diabetes, cirrhosis and desferrioxamine use predispose to bacteraemia.
• Incubation is 4 to 7 days.

Fever, diarrhoea (watery or bloody), and right lower quadrant pain mimicking appendicitis (pseudoappendicitis) lasting 1 to 3 weeks, with excretion up to 3 months.

• Pharyngitis, erythema nodosum and arthralgia in adults.
• Differential diagnosis: appendicitis, Crohn disease, Campylobacter, Salmonella, Shigella, tuberculous ileitis, lymphoma, amoebic colitis.
• Complications: bacteraemia and metastatic abscesses (liver, spleen), reactive arthritis (HLA-B27 positive adults), erythema nodosum, Reiter syndrome, thyroiditis, glomerulonephritis, intestinal perforation, ileal stricture, intussusception.

Stool culture on cefsulodin-irgasan-novobiocin agar with cold enrichment (4 C for 3 weeks); PCR panels increase detection. Alert the laboratory.

• Blood cultures if febrile and septic.
• Serology (agglutinin titres) for reactive complications.
• Ultrasound or CT to show terminal ileal and caecal wall thickening, enlarged mesenteric nodes and a normal appendix.
• Full blood count, CRP, iron profile in recurrent bacteraemia.

Supportive: oral or intravenous rehydration; analgesia; observation to avoid unnecessary appendicectomy when imaging shows a normal appendix.

Pharmacological

• Uncomplicated enterocolitis resolves in 1 to 3 weeks without antibiotics.
• Severe, prolonged or high risk illness: ciprofloxacin 500 mg twice daily for 5 to 7 days (IV 400 mg every 12 hours), or cotrimoxazole 960 mg twice daily for 5 to 7 days, or doxycycline 100 mg twice daily.
• Septicaemia or focal infection: ceftriaxone 2 g IV daily plus gentamicin 5 mg/kg IV daily for at least 2 to 3 weeks, then oral ciprofloxacin 500 mg twice daily to complete 3 weeks to 6 weeks (focal abscess).
• Reactive arthritis: naproxen 500 mg twice daily; refractory cases sulfasalazine 1 g twice daily.
• Children: cotrimoxazole 4 mg/kg trimethoprim twice daily, or cefotaxime 50 mg/kg every 8 hours for bacteraemia.

Special groups: iron overload and haemodialysis patients (avoid desferrioxamine; use deferasirox cautiously); pregnancy (cephalosporin).

Red flags: sepsis, abscess, perforation, abdominal mass or obstruction.

Follow-up: review at 1 to 2 weeks; repeat blood cultures for bacteraemia; assess joints at 4 weeks.