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Melioidosis, the mimicker of maladies

Indian Journal of Medical Research, Mar 2004 by John, T Jacob

The diagnosis of an infectious disease is incomplete without determining its aetiology. Whether it is as simple as pharyngitis, or life-threatening as meningitis, aetiology determines therapy. We all know that physicians often take short cuts, and offer shotgun therapy without detecting or deducing the pathogen involved. For some diseases, the diagnosis is integrally linked with aetiology, such as tuberculosis and typhoid fever. So it is with melioidosis too; laboratory evidence is essential to diagnose and diagnosis is essential to choose the right antimicrobial. Wrong diagnosis is often a fatal mistake-mistake for the doctor, fatal for the sick who trusted the doctor

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Melioidosis is the name applied to any of a spectrum of diseases caused by infection due to Burkholderia pseudomallei. It may be recurrent or prolonged fever with or without lymphadenitis, pyogenic abscess(es) of liver, spleen, brain, skin, subcutaneous or any other tissue, osteomyelitis, pneumonia or septicaemia with or without multi-organ failure. Clinically these diseases mimic pyogenic bacterial infections, Gram negative septicaemia or cryptic tuberculosis. It is so easy to assign incorrect aetiology in any of these conditions and treat accordingly. Patients with localised superficial abscesses may recover with incision and drainage, but later on melioidosis may recur in another form. Some develop recurrent fever and weight loss, simulating tuberculosis, especially when accompanied by lymphadenopathy. Or they may come with, or deteriorate by rapidly developing, florid pneumonia or septicaemia with multi-organ failure and die in spite of the usual treatments. Even when investigated, the diagnosis may be missed unless the microbiologist is aware of the presence of this pathogen in all parts of India and for that reason speciales the microbe in hand. Bacteriology may show motile and nonfermenting Gram-negative bacilli, often mistaken for Pseiidomonas species and either treated as such or ignored considering them as contaminants. Treatment with the combination of broad-spectrum penicillin plus an aminoglycoside is common practice in such cases of suspected or detected Gram-negative sepsis, but it is usually of no help in melioidosis. Histopathology may show granuloma and necrosis mimicking caseation, suggestive of tuberculosis, but without acid-fast bacilli. Antitubercular treatment also fails. Melioidosis has to be treated with ceftazidime, a third generation cephalosporin, followed by trimethoprim-sulfamethoxazole for several weeks to prevent relapse. For some reason, B. pseudomallei is inherently resistant to most other antimicrobials.

It was an Indian bacteriologist, CS Krishnaswami, who first detected and described the microorganism in 1912, while working with a physician colleague, A Whitmore, under the British Army in Burma1.Tt was called Bacillus whi/mori, a name that did not last long. But it remained assigned to the genus Bacillus for decades and later shifted to the genus Pseudomonas.Until 1992 it was classified as Pseudomonas pseudomallei. Currently it is included in a newly named genus of Burkholderia, a name given in honour of the American microbiologist who identified a bacterial infection of onions that turned out to be another species included in this genus. The first report of the presence of B. pseudomallei in India was not from an Indian laboratory, but from Scotland in 19532, reflecting the decline in our quest for excellence in diagnostic microbiology even in academic institutions. The second report of its presence came from Germany in 19883. In both instances, a traveler got infected here, but the disease manifested later after return to Scotland and Germany respectively, and was aetiologically diagnosed in these countries. The credit of the first report from an Indian centre goes to KR Raghavan and colleagues in Mumbai4.

B. pseudomallei is a soil saprophyte. Infection may be via skin through abrasions or by inhalation. During the American invasion of VietNam many soldiers were infected and manifested pulmonary or other forms of melioidosis after return from war duty. Helicopter borne soldiers were especially prone to lung disease, presumably due to the inhalation of dust raised by landing helicopters, for which reason the disease was nicknamed 'VietNam tuberculosis'. Others fighting in VietNam developed various forms of melioidosis, usually years after return to the USA. Therefore it was also nicknamed 'VietNam time bomb'. The Scottish, German and VietNam reports illustrate that infection may remain latent for prolonged periods and later manifest with disease, mimicking tuberculosis. Diabetes mellitus, chronic renal failure and cirrhosis of the liver seem to predispose the activation to disease of the otherwise dormant latent infection. Many subjects with melioidosis are otherwise in good health, showing that B. pseudomallei is actually a primary pathogen. It is well recognized in most south east Asian countries and in northern Australia. In northern Thailand, melioidosis is the most common cause of septicaemia. Now we know that its geographic prevalence does not stop at Myanmar but extends to most of India.

Melioidosis, the mimicker of maladies

Indian Journal of Medical Research, Mar 2004 by John, T Jacob

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