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Melioidosis

Author: Dr Catriona Wootton, Consultant Dermatologist, UK. DermNet NZ Editor in Chief: Adjunct A/Prof Amanda Oakley, Hamilton, New Zealand. April 2019. 


Introduction

Melioidosis and glanders are infectious diseases with similar clinical presentations, caused by species of the bacterial genus Burkholderia. In nature, the two diseases differ in their geographical spread and ecology.

What is melioidosis?

Melioidosis is an uncommon tropical disease caused by the bacterium, Burkholderia pseudomallei (formerly Pseudomonas pseudomallei and Malleomyces pseudomallei). Melioidosis is endemic in Southeast Asia and northern Australia, and cases also occur in the South Pacific, Africa, India, the Middle East, Central and South America. It has the potential to produce fatal disease and is considered a potential biological warfare agent because it is highly infectious, especially by inhalation [1].

Melioidosis is also called Whitmore disease, Vietnamese time bomb, Nightcliff gardener's disease, morphia injector’s septicaemia, and paddy-field disease.

Melioidosis

Who gets melioidosis?

Melioidosis predominantly occurs in people who have frequent contact with soil or surface water, such as workers in rice paddies, particularly during the rainy season. Travellers to rural areas in endemic countries may be at risk, if they come into contact with contaminated soil or water, especially if they are immunosuppressed or have a chronic condition such as diabetes, liver or kidney disease or chronic lung disease [1]. Historically, melioidosis has also been described as being transmitted via intravenous drug use, but this is now extremely rare.

How is melioidosis acquired?

B. pseudomallei can be acquired by humans and animals via contact with contaminated soil (especially through skin abrasions), inhalation of dust and ingestion or aspiration of contaminated water. Person-to-person transmission is very rare. The organism is categorised in Hazard Group 3, so specimens from patients with suspected melioidosis must be handled in a containment laboratory to reduce the risk of laboratory-acquired infection.

What are the clinical features of melioidosis?

Most cases of melioidosis in endemic areas are recently acquired (within a few days)However, the incubation period for melioidosis can range up to many years. The disease may develop following surgery, during intercurrent illness or at times of stress years after exposure, as has been well documented in US servicemen who served in Vietnam [2]. The different presentations of the disease are discussed below. 

Asymptomatic

In healthy people, exposure to B. pseudomallei may be associated with asymptomatic seroconversion.

Localised infection

Localised infection with melioidosis results from direct inoculation through a skin abrasion.

  • A nodule, ulcer or abscess develops at the site of entry.
  • The infection is associated with fever and muscle pain.
  • It can progress to bloodstream infection (septicaemia), osteomyelitis, meningitis, brain, liver or spleen abscesses.

Pulmonary infection

Pulmonary infection is the most common presentation for melioidosis.

  • Lung infection can range from mild bronchitis to severe pneumonia.
  • Chest pain, cough, fever, headache, loss of appetite, and muscle pain are common.
  • The lung infection can become chronic and may be mistaken for tuberculosis.

Septicaemia

Septicaemia or acute bloodstream infection is the most severe form of melioidosis.

  • It occurs mainly in people with underlying chronic conditions such as liver or kidney disease.
  • Symptoms are often non-specific but generally include fever, breathing difficulties, headache, diarrhoea, abscesses on the skin and throughout the body, muscle pain, and confusion.
  • The onset of septicaemia is rapid and often leads to septic shock.
  • The mortality rate for septicaemic melioidosis can exceed 80%.

Disseminated infection

In disseminated melioidosis, abscesses develop in various body sites, such as skin, lymph nodes, muscle, brain or internal organs (especially liver, spleen, lung and prostate).

  • It can occur with acute or chronic melioidosis.
  • Symptoms include fever, weight loss, abdominal pain, chest pain, muscle and joint pain, headache and seizures.


What are the complications of melioidosis?

Melioidosis can be life-threatening. The risk is increased with:

  • More extensive or severe disease
  • Comorbidities such as chronic diseases (diabetes, chronic lung disease, liver or kidney disease) or immunosuppression.

Complications of melioidosis include:

  • Sepsis
  • Organ failure
  • Pneumothorax
  • Cardiac tamponade
  • Recurrence of infection.

How is melioidosis diagnosed?

Culture from blood, sputum or other infected sites will confirm the diagnosis.

  • A full screen should be sent for culture (blood, sputum, urine, throat swab, any aspirated pus). Selective media increase the yield from non-sterile sites.
  • Serology is only of benefit in patients from non-endemic areas or if seroconversion can be demonstrated.
  • Laboratories must be informed of the suspected diagnosis for two reasons. Firstly, the organism may be dismissed as an environmental contaminant by the unwary, and secondly to ensure the use of appropriate media and laboratory containment.

What is the differential diagnosis for melioidosis?

Any infectious disease causing fever, headache, muscle pain with pneumonia, abscesses or skin involvement could be included in the differential diagnoses for melioidosis, including:

What is the treatment for melioidosis?

Antibiotics are the mainstay of treatment for melioidosis. Currently, ceftazidime is the treatment of choice during the acute phase.

  • Antibiotics are given intravenously initially for the first 10–14 days.
  • They are then changed to oral treatment, usually trimethoprim-sulphamethoxazole, for 12–20 weeks.
  • Continuous antibiotic treatment is required for several months in order to prevent relapse.
  • Severe cases may require admission to an intensive care unit for supportive therapy.
  • Abscesses may require surgical drainage.

Prevention of melioidosis

There is currently no effective vaccine for melioidosis.
The risk of exposure to B. pseudomallei can be minimised by:

  • Avoiding contact with soil and standing water in endemic areas. This especially applies to people with open skin wounds or chronic health conditions.
  • Agricultural workers in endemic areas wearing rubber boots when working.
  • Appropriate use of personal protective measures by healthcare and laboratory staff.

What is the outcome of melioidosis?

The septicaemic form of melioidosis carries a very high mortality risk (90%) if not appropriately treated.
There is the potential for the disease to recur in patients many years after the initial infection, including in patients who were asymptomatic originally.
Scarring may occur from chronic skin lesions.

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References

  1. Wiersinga WJ, Virk HS, Torres AG, Currie BJ, Peacock SJ, Dance DAB, Limmathurotsakul D. Melioidosis. Nat Rev Dis Primers 2018; 4:17107. DOI: 10.1038/nrdp.2017.107. PubMed. PMC Central.

  2. Allen C. Cheng, Bart J. Currie. Melioidosis: Epidemiology, Pathophysiology, and Management. Clin Micro Rev 2005;18(2):383-416. DOI: 10.1128/CMR.18.2.383-416.2005. PubMed. PMC Central. Journal.

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