Yersinia Infections

Yersinia are Gram negative bacilli.¹ All are uncommon in UK.^2,3 Three Yersinia spp. cause infection in man:⁴

• Yersinia enterocolitica: causes gastroenteritis
• Yersinia pseudotuberculosis: causes mesenteric lymphadenitis
• Yersinia pestis: causes plague

• Although organism is found in wide range of domestic animals, the commonest source of infection for man is the pig.
• Found in many countries worldwide, but mainly in cooler climates, particularly Canada, Northern Europe and Japan.
• Mainly sporadic but outbreaks can occur. Infection is usually caused by eating or drinking food or water contaminated with faecal material. Cause gut infections usually through food borne infection.⁵ Undercooked pork is a major risk factor.

Presentation

• Incubation period is 3-7 days. Often presents with acute gastroenteritis.
• Diarrhoea , fever and abdominal pain, which last for up to three weeks.⁴
• Older children may present with mesenteric adenitis and terminal ileitis, mimicking appendicitis, usually without diarrhoea.
• May develop bacteraemia and focal infections.

Investigations

• Stool culture
• Serology; a rising titre of Y. enterocolitica antibodies is strongly suggestive of acute yersiniosis but this result is usually delayed until after recovery

Management

• Self-limiting infection in otherwise healthy patients.
• In patients with localised infection and bacteraemia: aminoglycosides, chloramphenicol, tetracycline, co-trimoxazole, third generation cephalosporins and fluoroquinolones.

Complications

• Reactive polyarthropathy and erythema nodosum are common.

• Also causes gut infections but is much less common and contracted from animals and birds.
• Distribution is worldwide but notable outbreaks have occurred in Finland, Japan and Czechoslovakia.
• More common in 5-20 year olds.

Presentation

• Often presents as mesenteric lymphadenitis (mimics acute or subacute appendicitis).
• Occasionally causes erythema nodosum and polyarthritis.

Investigations

• Stool culture
• Serology

Management

• Treatment is usually not necessary.
• Ampicillin, cephalosporins or aminoglycosides in immunocompromised.

Prognosis

• Usually self limiting illness in healthy individuals.
• Often associated with chronic illness and high mortality rate in the immunocompromised.

Now mainly limited to animals but occasionally causes disease in humans. Still occurs in parts of Africa, India, China and Far East and South America. The main reservoirs for infection are woodland rodents, which can transmit the bacteria to urban rat populations. The rat flea, Xenopsylla cheopic, acts as the vector. The rat fleas may bite humans and humans may also become infected by wound contact with infected faeces or by droplet inhalation.

Presentation

• Bubonic plague is the most common form of infection:
  • The incubation period is about one week.
  • Presents with fever, chills, weakness, myalgia, nausea, vomiting and headache.
  • Acute tender lymphadenitis (buboes), especially inguinal, axillae or neck lymph nodes. Affected lymph nodes suppurate within one to two weeks.
  • The patient is usually severely ill, restless or agitated.
  • Seizures are common in children.
• Pneumonic plague: infection is from the breath of an individual with septicaemic or pneumonic plague. Causes fulminant pneumonia with bloody sputum, marked cyanosis and high fever. Most patients will die if not treated.
• Septicaemic plague: fulminant acute infection. Causes disseminated intravascular coagulation and shock. Death usually occurs within two to five days if no treatment is available.
• Cutaneous plague: pustule, eschar, papule or an extensive purpura. The lesion may become necrotic and gangrenous.

Investigations

• Full blood count; raised white cell count with neutrophils predominant
• Culture of bubo aspirate

Management

• Gentamicin, streptomycin, ciprofloxacin and doxycycline are effective but must be started within one day of the onset of infection.

Prognosis

• Y. pestis has 50% mortality if untreated.
• Can cause death in 2-4 days.

Prevention of plague

• Control of the flea population. The flea population must be controlled before the rodents are killed because the fleas will leave the dead rat carcasses and will instead bite humans.
• Chemoprophylactic agents, e.g. tetracycline or sulphonamides.
• For travellers to endemic plague areas there is partially effective formalin-killed vaccine available.
• Isolation: patients with plague can themselves be infective.