Melioidosis

Question 1

What is the causative agent of melioidosis?

Answer 1

Burkholderia pseudomallei

Question 2

what is the incubation of melioidosis?

Answer 2

Typically, 9 days; range is 1 21 days. May remain latent for months to years before symptoms develop.

Question 3

how is burkholderia pseudomallei transmitted?

Answer 3

Transmission occurs through direct inoculation of contaminated soil or water through small cuts or abrasions, inhalation of contaminated soil dust, or through ingestion or aspiration of contaminated water.

Question 4

What are the risk factors for acquiring burkholderia pseudomallei?

Answer 4

• Occupational (e.g. military, farming, construction work), recreational (e.g. adventure travellers) or other contact with soil or surface water is a risk factor.
• Those with underlying medical conditions, such as diabetes mellitus, chronic renal disease and chronic lung disease, are recognised to be at increased risk of the disease.

Question 5

What are the clinical features of melioidosis?

Answer 5

The presentation of melioidosis is variable and can mimic many other conditions (e.g. tuberculosis).

• Melioidosis infections can be subclinical.
• Common presentations include pneumonia and localised skin ulcers or abscesses.
• It should also be considered as a differential in a patient presenting with visceral abscesses (e.g. liver, spleen, kidney, prostate).
• Other presentations include osteomyelitis and meningoencephalitis.

Patients are often bacteraemic and can develop a fulminant infection with septic shock. The mortality rate is high in these cases.

Some patients may present with a relapse even after appropriate antibiotic therapy for the initial episode of infection.

Question 6

What are the investigations for meliodosis?

Answer 6

Culture and sensitivity remain the mainstay of diagnosis

• In symptomatic at-risk patients, send samples from variety of sites; consider these: blood, sputum, urine, ulcer swab, abscess fluid, throat swab, rectal swab
• Microscopy: Gram stain shows GNR and characteristic bipolar staining with a “safety pin” appearance

Serology (e.g. indirect haemagglutination test) is not a reliable method of diagnosis.

CT, U/S (other imaging)

• CT AP should be performed routinely in all adult patients with confirmed or suspected melioidosis, to evaluate for asymptomatic abscesses in the prostate, spleen, liver, and kidneys
• U/S abdomen: in children and adult females who are not systemically ill, an abdominal ultrasound may be used as an alternative to CT scan to avoid radiation exposure

Question 7

How are patients with melioidosis managed?

Answer 7

• Patients require long courses of antibiotics.
• In the initial intensive phase of therapy, intravenous antibiotics (ceftazidime or meropenem) are given for at least 2 weeks.
• This is followed by oral eradication therapy, trimethoprim/sulfamethoxazole, for 3-6 months.
• In the presence of intolerance or contraindication, amoxicillin-clavulanate is a less effective oral alternative (ensure dosing is adequate).
• Abscesses should be drained when possible.