Pseudomonas pseudomallei (aka Burkholderia pseudomallei) - MegaMicro
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Pseudomonas pseudomallei (aka Burkholderia pseudomallei)
Microbiology > Bacteriology > Gram-negative bacteria > Gram-negative bacilli > Pseudomonas
P. pseudomallei (also called Burkholderia pseudomallei)
a. Structure
i. Gram negative, rod-shaped, bipolar
ii. Smooth form appears as long parallel bundles and rough form appears more irregularly arranged
iii. Has two chromosomes (most bacteria have one!)
b. Pathobiology:
i. Oxidase-positive
ii. Catalase-positive
iii. Motile
iv. Aerobic
v. Non-spore forming
vi. Saprophytic
vii. Incubation time ranges from days to years
viii. Grows best on pH neutral to slightly acidic
ix. Virulence factors:
1. Burkholderia lethal factor 12. Capsular polysaccharide I3. Cluster I type VI secretion system4. Bsa type III secretion system5. Burkholderia intracellular motility factor A (BimA) – required for actin-based motility6. Filamentous hemagglutinin – helps adhere to host epithelial cells
c. Epidemiology
i. Soil-dwelling endemic in tropical and subtropical regions – particularly Southeast Asia (Thailand, Vietnam) and Northern Australia
ii. Can infect both animals and humans through direct contact via inhalation, ingestion or open wounds
d. Laboratory diagnosis
i. Definite diagnosis can be made by culturing the organism from any sample, because the organism is never part of normal human flora .
e. Disease manifestations
i. Causes Melioidosis, also called Whitmore’s disease
1. Melioidosis is associated with tropical climates (esp. Southeast Asia)2. Bacteria is found in contaminated water and soil3. Spread to humans and animals through direct contact with the contaminated source4. Symptoms are diverse – range from mild, localized skin infection to more severe, fatal presentations including septic shock, internal abscess and neurological involvement5. Commonly causes abscesses in the lung, bronchitis or pneumonia6. Patients typically present with fever and bloody sputum.7. Can also cause blood disease, kidney disease, heart disease, etc.
ii. Diagnostic methods
1. Diagnosed by isolating P. pseudomallei from the blood, urine, sputum, or skin lesions2. Also can be diagnosed by detecting and measuring antibodies to the bacteria in the blood
iii. Differential diagnosis
1. Clinically similar to Ganders disease – but the ecology and epidemiology are different
a. Ganders is contracted by humans from infected domestic animalsb. Glanders is caused by Burkholderia mallei
F. Therapy
1. Treatment is divided into two stages:
a. IV intensive phase – IV ceftazidime (cephalosporin, 3rd gen) or IV meropenem (β-lactam)i. Given for 10-14 days until the patient’s temp has returned to normalb. Eradication phase – treatment with co-trimoxazole (sulfonamide) and doxycycline (tetracycline) for 12-20 weeks to reduce recurrence
2. Requires combination of antibiotics because the bacteria is resistant to most antibiotics – treatment usually lasts over a month3. Surgically drain any abscesses
E. Prevention and control
1. Currently no vaccines available2. In endemic areas, avoid contact with soil, mud, and surface water3. Populations at risk are patients with diabetes mellitus, chronic renal failure, chronic lung disease, or immune deficiency of any kind4. Wear boots if possible
Related concepts
- Gram-negative bacteria
- Gram-negative bacilli
- Pseudomonas
- P. pseudomallei
- Tropical
- Melioidosis
- Soil
- Burkholderia pseudomallei
Web links:
1. Burkholderia pseudomallei Info (Missouri S&T Microbiology): http://web.mst.edu/~microbio/BIO221_2010/B_pseudomallei.html
a. Useful for pictures
2. Melioidosis Info (CDC): https://www.cdc.gov/melioidosis/
a. Very thorough source
