In the third category, the subclinical group, if an individual comes to medical attention at all, a chest roentgenogram may strongly suggest tuberculosis with upper lobe infiltrate and/or cavitation (Figs. 23.20, 23.21, 23.22). There may be a localized segmental density or ill-defined infiltrate with one or more cavities.

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Fig. 23.19 Subclinical melioidosis in a 29-year-old white American soldier who had a nodular infiltrate discovered in Vietnam in October, 1966. He was initially thought to have tuberculosis and was transferred to a military hospital in the United States where B. pseudomallei was isolated. Tuberculosis work-up was negative. He was placed on appropriate long term antibiotic therapy with subsequent reduction in size of the infiltrate, but he developed very thin-walled cavities which remained open as late as December 1967 (14 months later), although he had long since been asymptomatic. A Apical lordotic view of the chest on October 13, 1966 shows a soft nodular infiltrate in the right upper lobe, mimicking tuberculosis. B AP tomogram of the right upper lobe reveals cavitation within this area of infiltrate and stranding towards the right hilum as well as towards the apex. C PA chest film of November 10, 1966 shows the cavitary process in the right upper lobe, partially hidden by the right first rib and clavicle. D Despite long-term antibiotic therapy, an AP tomogram of the right upper lobe on August 1, 1967 shows a persistent thin-walled cavity without significant surrounding inflammatory reaction. There is fibrolinear stranding towards the apex and the hilum. This cavity persisted for at least 5 more months, when the patient was lost to follow-up.

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Fig. 23.20 A,B Subclinical melioidosis in a 33- year-old American soldier serving in Vietnam who presented with a fever of undetermined origin without other significant symptoms. A PA chest film and B AP tomogram of the right upper lobe revealed a small nodular infiltrate in the lateral aspect of the right upper lobe with cavitation. Although initially thought to be most likely tuberculosis, this lesion was subsequently proven to be due to melioidosis, essentially of the subclinical type. C Photomicrograph of a nodular lesion of the lung in another patient shows an area of necrosis bordered by epithelioid cells, presenting an appearance resembling tuberculosis. Bacilli are seldom found in these more chronic lesions of melioidosis. AFIP 69-5775.

Fig. 23.21 Subclinical melioidosis presenting as a cavitary infiltrate in the right lower lung in a 19-year-old male soldier seen at a military hospital in Vietnam with a cough but no fever or other symptoms. Tuberculin skin test was negative, but the melioidosis titer was positive at 1:80. (Courtesy of Dr. Preston Mayson, Roanoke, Virginia).

Fig. 23.22 Subclinical melioidosis which had remained dormant for 5-6 years before becoming reactivated with patchy infiltrates throughout the right lung associated with cavitation. The patient was a 40-year-old American soldier hospitalized in December 1965 with a 2 week history of cough productive of grayish sputum and a fever of 40°C (104°F). He had been stationed in Southeast Asia in 1959-1960 and since then had resided only in the United States. Sputum examination was positive for B. pseudomallei, and melioidosis serology and complement fixation tests were positive. He was treated for 1 month with tetracycline with resultant clearing. Chest radiograph on January 5, 1966, shows soft, patchy infiltrates in the right apex and right mid and lower lung fields with tiny nodular densities also seen throughout the right lung. There is a large area of cavitation in the lateral aspect of the right midlung with a small air-fluid level within the abscess cavity. Such cases as this indicate that occasional cases of melioidosis may be seen in patients many months or years after they have traveled to, or resided in, endemic regions of Southeast Asia. The occasional cases of melioidosis reported in countries outside Southeast Asia have mostly been in patients with subclinical disease who once lived or served in Southeast Asia.

In the fourth category, consisting of patients with chronic, usually extrapulmonary infection, the most common manifestations are subcutaneous and deep abscesses, draining sinuses, osteomyelitis, septic arthritis, and nodules or purulent abscesses in the lungs, liver, spleen, pancreas, kidneys, testis, prostate and brain. When the lungs are involved, the radiological appearance may be that of an unresolved pneumonia, a chronic infiltrate without hilar adenopathy or pleural effusion, or a cavitary lesion or lung abscess, usually in an upper lobe.

The computed tomography (CT) findings in 5 patients with melioidosis were reported by Singcharoen (1989). Pulmonary lesions consisted of an upper lobe infiltrate with a small thin-walled cavity in 2 patients and lower lobe consolidation without cavitation in another individual. Pleural lesions included a small pleural nodule, effusion with associated lung lesion, hydropneumothorax as a complication, and end-stage fibrothorax from chronic empyema. Hepatic and splenic microabscesses were identified in one patient.