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Melioidosis:
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Bacterial weapon acting on humans and livestock |
Synopsis, Diagnosis, Symptoms,
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Safety Precautions for Melioidosis Casualties |
Standard Precautions defined by the 1996 CDC guidelines should be adopted for handling patients.Biosafety level 2/3 practices should be adopted for handling of samples. |
| Causative organism: (Systematic name in 1997) |
Burkholderia pseudomallei |
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| Older names: |
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| Alternative names for the disease: |
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| Properties: | Gram-negative, bipolar, aerobic flagellate bacillus, motile, non-spore-forming.
(Cells stain red in the Gram stain with the stain more intense at the ends, they require oxygen for growth, are rod-shaped, and have hair-like structures called flagellae on their surface that they use to move under their own power, and does not form spores) |
| Antibiotic treatments: |
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| Vector involvement: | None |
| Epidemiology of natural outbreaks: | The disease is largely unknown outside Southeast Asia and is typically found in men who have spent a great deal of time working rice paddies. About 9% of all men tested in Indo-China had antibody to the organism without any history of the disease. Approximately 350 cases were seen in US servicemen in Vietnam with about 10% dying. |
The disease can present an extremely wide variety of symptoms. Common clinical features are sepsis (blood stream infection), pneumonia, liver abscess, splenic abscess, skin & soft tissue abscess and chronic fever. In acute cases, the organs showing most damage are the lungs. Specific diagnosis (differentiating it from B. mallei) can be made only by characterization of the isolated organism. B. pseudomallei grows slowly in culture and the patient may die before confirmation. Histological examination of lesions may show cells with damaged nuclei and chromatin extruded from the cells.
Bacilli showing bipolar (safety pin) staining with methylene blue or Wayson's or Wright's stain may be found in exudates.
The disease may look like typhoid fever or tuberculosis and these possibilities must be eliminated.
There are currently no rapid immunochemical assays for the bacterium.
Symptoms and effects.
Presentation of melioidosis can be highly variable and the disease shares with syphilis the designation of the "Great Imitator."
An acute case of the disease may be indicated by a sudden onset of chills, headache, fever, muscle and joint pain and rapid prostration (exhaustion). A cough or hard breathing, nausea and vomiting may follow. The disease may misidentified as typhoid fever or tuberculosis because it has a number of features in common with them, including lung damage (pulmonary cavitation) leading to emphysema, chronic abscesses, and osteomyelitis (inflammation of the bone marrow).
In the case of an airborne attack the most likely form of the disease will be pulmonary. Pulmonary melioidosis can range from bronchitis to a severe pneumonia (filling of the lungs with fluid) accompanied by necrosis (tissue death). There is almost always a fever of ›38.9°C (102°F) and some form of chest pain. Onset can be slow or abrupt. Rales and tachypnea (rapid shallow breathing) are common signs. A wide range of damage to the lungs have been seen. Much of the damage, such as pulmonary cavitation, is confined to the upper lobes of the lungs.
An acute septicemic form of the disease is seen in intravenous drug users, alcoholics and diabetics. It may include symptoms of the pulmonary form and other soft tissues may show inflammation including meningitis. This form is rapidly fatal, even with antibiotic treatment.
Medical and Physical Countermeasures.
Vaccination (Immunoprophylaxis)
A vaccine is not available.
Antibiotics
Antibiotics can be effective after infection with a combination of a tetracycline (terramycin or aureomycin) and the chloramphenicol derivative chloromycetin. Sulfadiazine may be used in addition in severe cases. Prolonged antibiotic therapy with doxycycline, followed by trimethoprim/sulfamethoxazole followed by chloramphenicol may be needed to prevent relapse. Relapse is found in about 20% of cases.
Antibiotic Resistance
Resistance to penicillins is common in B. pseudomallei and multiply antibiotic resistant strains have been found in nature.
Supportive care
Drain lesions as necessary, If sputum cultures are not clear after 6 months of antibiotic treatment surgical removal of lung tissue may be necessary.
Decontamination
The microorganism can be killed by moist heat at >74°C (165°F) or with disinfectants.
Agent Properties and Potential Uses.
The bacterium is native to moist soils of the tropics and is relatively unknown in the west and most people have no natural immunity to it. The bacterium is resistant to dry heat and can survive for a month in dry soil, water or rodent excrement. The primary route of infection is through contaminated food making battlefield weaponization unlikely.
Terrorist Acquisition and Attempted Use.
| Disease | ICD-9-CM | ICD-10 |
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| Melioidosis | 025 | A24.1 |
| Acute or fulminant melioidosis | A24.1 | |
| Subacute or chronic melioidosis | A24.2 | |
| Other specified manifestation of melioidosis | A24.3 | |
| Melioidosis, unspecified | A24.4 |
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