Multisystem Bacterial Infections

 

• Typhoid and paratyphoid fever

  Aka enteric fever.

  Pathophysiology and epidemiology

  • Systemic Salmonella infection with S. typhi or S. paratyphoid.
  • After malaria, commonest serious tropical disease in returning travellers from Asia (esp. South and Southeast); also found in Africa and South America.
  • 1-3 weeks incubation.
  • Not to be confused with typhus, an infection by Rickettsia typhi.

  Presentation

  Typhoid fever:

  • Insidious onset of fever, headache, malaise, and constipation. Diarrhoea and vomiting can occur but are less common.
  • Other features: rose spots (macules on chest and abdo), hepatosplenomegaly, lymphadenopathy, dry cough, neurological symptoms, bradycardia.

  Paratyphoid fever:

  • Similar to typhoid fever, but more abrupt onset and milder course.

  Investigations

  • Blood and stool cultures.
  • FBC and LFTs may be deranged.

  Management

  Azithromycin or ceftriaxone.

• Leptospirosis

  Pathophysiology and epidemiology

  • Infection with the spirochete genus Leptospira.
  • Transmitted to humans in urine of rats, dogs, and other mammals, either directly or in urine-contaminated water.
  • Can be acquired in the UK, but most UK cases are acquired abroad.
  • 1-2 weeks incubation.

  Presentation

  • Biphasic course, with bacteraemic flu-like phase followed 1-3 days later by immune phase.
  • Immune phase may be mild (e.g. fever and myalgia), but severe manifestations include Weil's disease, characterised by haemorrhage, conjunctival suffusion (redness without exudate), jaundice, and hepatorenal failure.
  • Less commonly, there may be GI, respiratory, or CNS manifestations.

  Investigations

  • FBC: ↑neutrophils, and sometimes ↓Hb and ↓PLT.
  • Deranged renal and liver function tests.
  • Diagnosis: IgM serology (>7 days).

  Management

  • Penicillins or tetracyclines.
  • Antibiotics are still given in the immune phase, despite the fact that they may confer little benefit.

• Whipple's disease

  Pathophysiology and epidemiology

  • Infection by the Gram +ve rod Tropheryma whipplei.
  • Ubiquitous in environment, and often linked to soil or animal exposure e.g. farmer.
  • Minimal immune response by patients suggests specific immunodeficiency as a risk factor.
  • Patients are 90% male, mean age 50, usually white.

  Presentation

  Common:

  • Joints: typically migratory large joins arthralgia, which may precede other symptoms by >5 years. Often misdiagnosed as a seronegative arthritis.
  • GI: chronic intermittent diarrhoea, colicky abdo pain, malabsorption, weight loss.

  Less common:

  • CNS: usually dementia/confusion, less commonly, ophthalmoplegia, nystagmus, seizures, myoclonus.
  • Cardiac: usually endocarditis, less commonly myo/pericarditis.
  • Others: fever, lymphadenopathy, skin hyperpigmentation, cough, uveitis.
  • In rare cases, it can present with one/some of these features alone.

  Investigations

  • Bloods: ↓Hb, ↑WBC, ↑CRP, ↑PT (vit K malabsorption).
  • Diagnosis is by tissue biopsy, usually small bowel from upper GI endoscopy, testing sample with Periodic acid‐Schiff stain (+ve) and PCR.
  • CSF PCR in all, due to potential morbidity of CNS involvement. Other sites only sampled (e.g. joints, lymph nodes) if symptomatic and GI features absent.
  • Very difficult to culture, so even in endocarditis it is only diagnosed from histology of resected valves.

  Management

  Antibiotics IV – e.g. 2 weeks ceftriaxone or penicillin – then 3-12 months co-trimoxazole PO.

  Complications and prognosis

  • Uniformly fatal without treatment.
  • Immune reconstitution inflammatory syndrome (IRIS) in first weeks of treatment.
  • Relapses, often in CNS, if inadequately treated.