Melioidosis Update From Australia
Abstract & Commentary
Synopsis: Melioidosis is endemic to northern Australia. Clinical presentations are similar to those in southeast Asia, often with pneumonia, genitourinary infections, abscesses, as well as encephalomyelitis. Underlying conditions such as diabetes mellitus, chronic lung disease, chronic renal disease, and excessive alcohol use are risk factors for developing the infection. Treatment with G-CSF may improve survival.
Source: Currie BJ, et al. Endemic melioidosis in tropical northern Australia: A 10-year prospective study and review of the literature. Clin Infect Dis. 2000;31(4):981-986.
In this prospective study of melioidosis in northern Australia from October 1989 to September 1999, 252 cases were identified. Common presentations were pneumonia (50%) and genitourinary infections (37%). Other presentations included skin abscesses (13%), osteomyelitis, and/or septic arthritis (4%), soft tissue abscesses (4%), and encephalomyelitis (4%). Prostatic abscesses were present in 18% of infected men. Bacteremia was present in 46% of the patients, and 19% of patients identified in the study died.
Risk factors for melioidosis included diabetes mellitus (37%), excessive alcohol use (39%), chronic lung disease (27%), chronic renal disease (10%), and consumption of kava (8%), a local euphoria-producing drink made from shrub roots. Twenty percent of patients did not have any known identifiable risk factors.
Treatment with ceftazidime or carbapenem antibiotics for at least 2 weeks, followed by at least 3 months of eradication therapy with trimethoprim-sulfa, was associated with decreased mortality. However, mortality was 86% among those with septic shock. Granulocyte-colony stimulating factor (G-CSF) given to 6 patients with melioidosis-associated septic shock appeared to improve survival.
Comment by Lin H. Chen, MD
Melioidosis was originally recognized in patients from Myanmar and subsequently described in Viet Nam, Indonesia, Singapore, Thailand, and Australia.1 The causative organism, Burkholderia pseudomallei, previously known as Pseudomonas pseudomallei, is a gram-negative bacillus easily isolated from soil and surface water in endemic areas.2 Humans and many species of animals can become infected. It is speculated that infection occurs by inoculation of wounds or mucosal surfaces with contaminated soil or water.3 In addition, it appears that inhalation of aerosolized material containing B. pseudomallei may cause infection.4
Clinical presentations of melioidosis include sepsis, pneumonia, parotitis, lymphadenitis, abscesses of internal organs including the liver, spleen, and brain, as well as skin and subcutaneous abscesses, osteomyelitis, and septic arthritis. Patients can present with acute infection after a short incubation, or reactivate from past exposures.
The majority of patients with symptomatic melioidosis have underlying diseases such as diabetes mellitus, chronic renal disease, liver disease, immunosuppressive treatments, malignancy, alcohol, and pregnancy. The association of melioidosis with diabetes was reviewed in detail in the January/February 2000 issue of Travel Medicine Advisor Update (see Bia FJ. TMA Update. 2000;10:5-8).
Diagnosis is difficult when based upon clinical findings alone. Culture of the organism is diagnostic. Serologic tests, such as indirect hemaglutination or enzyme-linked immunoassays, are also available. C-reactive protein can be followed while the patient is under treatment.
Antibiotic treatment of melioidosis should be initiated with ceftazidime or one of the carbapenem antibiotics for at least 2 weeks, followed by prolonged oral antibiotics, which are necessary to eradicate infection. Regimens used for eradication include trimethoprim/sulfamethaxazole, doxycycline, chloramphenicol, or amoxicillin/clavulanate. Abscesses must be debrided, and septic shock requires considerable supportive treatment. Mortality rates are high.
The current study shows some well-established disease characteristics, namely the male predominance, and the common presentations of pneumonia, septicemia, and abscess formation. In addition, some new findings are noted, including consumption of kava as a possible predisposing factor for developing melioidosis. Another is the unusual presentation of encephalomyelitis.
What information is useful to travel medicine specialists? Patients who have traveled to endemic areas, which includes northern Australia, may develop melioidosis from an acute infection as well as reactivate the infections from previous exposures. Melioidosis should be considered in the differential diagnoses of patients in whom exposure may have occurred and who present with sepsis, abscesses, or pneumonia unresponsive to usual treatments.7
1. Dance DA. Melioidosis: The tip of the iceberg? Clin Microbiol Rev. 1991;4:52-60.
2. Strauss JM, et al. Melioidosis in Malaysia II. Distribution of Pseudomonas pseudomallei in soil and surface water. Am J Trop Med Hyg. 1969;18:698-702.
3. Dance DA. Melioidosis. In: Guerrant RL, Walker DH, Weller PF, eds. Tropical Infectious Diseases: Principles, Pathogens, and Practice. Philadelphia, Pa: Churchill Livingstone; 1999:430-435.
4. Howe C, et al. The pseudomallei group: A review. J Infect Dis. 1971;124:598-606.
5. Chaowagal W, et al. Melioidosis: A major cause of community-acquired septicemia in northeastern Thailand. J Infect Dis. 1989;159:890-899.
6. Suputtanaongkal Y, et al. The epidemiology of melioidosis in Ubon Ratchathani, northeast Thailand. Int J Epidemiol. 1994;23:1082-1090.
7. Phetsouvanh R, et al. Melioidosis and Pandora’s box in the Lao people’s democratic republic. Clin Infect Dis. 2001;32:653-654.