Summary
Melioidosis is a bacterial zoonosis caused by the Gram-negative bacillus Burkholderia (Pseudomonas) pseudomallei, also called Whitmore bacillus. The infection can be acute, subacute, or chronic and affects the skin, the lungs, or the whole body. The disease is endemic in Southeast Asia and North Australia. Some cases have been reported in China but also at the Indian Ocean after the tsunami of December 26, 2004. A rising number of cases are reported in Europe. Men are predominantly affected (sex ratio: 1.4:1). Melioidosis may occur in any age group, but is more frequent between 40 and 60 years of age. The acute form of the disease is characterized by respiratory infections (necrotizing pneumopathy) and septicemia (with high fever, severe headaches, diarrhea, vomiting, lesions on the skin, and abscesses). The subacute and chronic forms are characterized by local abscesses and suppurative lesions most commonly affecting the lung (tuberculosis-like), liver, intestine, spleen, and also the skin, ganglia, brain and bones. Melioidosis is caused by Burkholderia pseudomallei, an environmental saprophyte in wet soil, mud, pooled surface water and rice paddies. Infection may occur through direct contact of skin abrasions, wounds and burns with contaminated soil or water but also by ingestion or inhalation. Often, diabetes, renal failure, thalassemia, and high alcohol consumption are independent risk factors for melioidosis. Incubation period varies from 2 days to months or years. The diagnosis is based on culture and identification of the pathogen. Other diagnostic methods include hemagglutination (IHA), direct immunofluorescence, enzyme-linked immunoabsorbent assays (ELISAs), complement fixation test or PCR assays. These methods can also help specify the prevalence of the infection in a given population. Imaging exams are performed to assess the full extent of disease. Differential diagnosis includes tuberculosis, pneumonia, and other infectious diseases such as plague, syphilis and typhoid fever. The pathogen is sensible to many antibiotics. Usually, trimethoprim-sulfamethoxazole (TMP-SMX or Co-Trimoxazole) is administered but in Thailand a high rate of resistance has been observed. Cephalosporin and imipenem are also used. Acute infections should be treated with ceftazidime antibiotherapy followed by prolonged course of oral antimicrobial therapy with Co-Trimoxazole. The prognostic is favorable if the disease is correctly and early diagnosed and treated. Relapses can occur and lifelong monitoring is recommended. Untreated patients with septicemia have fatal outcomes in 80% of the cases. Since 2002, Burkholderia pseudomallei is listed as a possible bacterial agent used in bioterrorism but with a lower risk than anthrax, plague and smallpox. * Author: Dr F. Trémolières (September 2009)*.
