Bacteria 7 (gram -ve): Melioidosis

Question 1

What bacterium causes melioidosis and where is this disease normally found?

Answer 1

Zoonotic disease: gram negative rod burkholderia pseudomallei

Disease constrained to SE Asia, up to 5000 cases per year in Thailand

Question 2

What is characteristic of the bacterium B. pseudomallei?

Answer 2

Question 3

How is melioidosis normally transmitted?

Answer 3

Causes 20% of community-acquired bacteraemia in NE Thailand; 3rd most common cause of death in NE after HIV/TB

• Close contact with contaminated water or ingestion/aspiration of water (drwoning)
• Aerosol inhalation

Risk groups: rice farmers, diabetics, alcoholics, those on steroids, those with liver/kidney disease

Question 4

What are predisposing factors to infection?

Answer 4

Patients infected by melioidosis have predisposing conditions in up to 70% of cases: DM (most common), CKD, cirrhosis, steroids, malignancy, no association with HIV

Question 5

How does it present clinically?

Answer 5

• Mostly asymptomatic: can stay latent within macrophages
• Acutely:
  a) localised disease -> abscesses (cutaneous melioidosis with solitary lesion at site of inoculation)
  b) septicaemic disease -> poor prognosis

Pneumonia is the most common manifestation

• Abscess at site of infection – especially parotid in children • Visceral abscesses can occur too
• Can develop into bacteraemia/septicaemia – mortality 50%

Question 6

How do you diagnose melioidosis?

Answer 6

Question 7

How do you treat melioidosis?

Answer 7

Often slow to respond to treatment

Sepsis mortality 50%

Treatment generally starts with intravenous antimicrobial therapy for 10-14 days, followed by 3-6 months of oral antimicrobial therapy., Eradication treatment is required for at least 12 weeks, Recurrent melioidosis is common and usually due to relapse following treatment failure to eradicate the infection, The first line treatment for IV therapy is ceftazidime

Question 8

MCQ key words?

Answer 8

A favourite MCQ: Remember Thailand, Paddy Field Work and Diabetes – the scenario may be a pneumonia not responding to conventional antibiotics.

• Parotid Abscess in a child in this setting may be a photograph based question.