Introduction

Melioidosis is caused by Burkholderia pseudomallei , a gram-negative bacilli, which is highly endemic in Southeast Asia. Melioidosis was studied as a possible biological warfare agent but was never used. B. pseudomallei  is easy to acquire from the environment by inhalation or ingestion of contaminated soil as well as contact through skin wounds. It is highly infectious, antibiotic resistance is readily manipulated, and there is no vaccine available for it. This bacterium is classified as category B priority pathogen by The National Institute of Health and the Centers of Disease Control and Prevention.

Clinical History

A 39-year-old male who is diabetic presented with complaints of sudden onset of shortness of breath grade IV. There was a history of high-grade intermittent fever and cough for 10 days. Bilateral lower limb swelling was there for past 1 month, andvenous Doppler showed bilateral popliteal vein thrombosis.

Clinical Examination

SpO2 83% room air.
Tachycardic and Tachypnoeic
RS: Bilateral basal crepts present.
The patient was intubated and stabilised, then shifted to radiology department for CT.

Ctpulmonary Angiogram

Axial section of chest CT shows multiple nodules of varying sizes noted randomly distributed in the bilateral lungs which show heterogenous enhancement post contrast. Smooth interlobular septal thickening was noted in the bilateral upper lobes

Consolidation with air bronchogram noted in the left lower lobe.
Patchy consolidation also noted in the lingula and right lower lobe posterior segment.
Bilateral minimal pleural fluid noted.
No evidence of pulmonary thromboembolism.

Based on CT finding, the suggested differentials are :

Tuberculosis
Septic embolism
Nodular metastasis

Laboratory Investigations:

Elevated CRP, D Dimer, procal , altered LFT and RFT
Blood culture showed Burkholderia pseudomallei

Discussion:

Melioidosis caused by Burkholderia pseudomallei , a gram-negative bacilli, can easily be confused with tuberculosis and various other infections. It can be misdiagnosed clinically, radiologically, and even in the laboratory. The most important factor leading to the diagnosis is a high index of suspicion. Melioidosis should be added in the differential diagnosis when an immunocompromised patient presents with febrile illness, localized suppurative process, and has a travel history or residence in an endemic area. Increased risk of infection is seen in a patient with comorbidities such as diabetes mellitus, excess alcohol intake, renal disease, and chronic lung disease.

The lungs are the most commonly affected organs in melioidosis, commonly presenting as pneumonia.

Abdomen: Affected viscera are often clinically enlarged but not as tender as with other pyogenic infections. The most common manifestations are abscesses. It affects liver , spleen, mesentry, pancreas, prostate., etc.

CNS manifestation  includes brain abscesses, meningitis, and encephalitis, particularly involving the brainstem.

Suppurative parotitis and later presents as an abscess.

Pulmonary Melioidosis

Stages

Radiologic Manifestation

Acute:

In acute septicemic melioidosis, the most common radiographic appearance is disseminated nodular lesions representing hematogenous spread. Rapid disease progression can result in abscess formation with cavitation.

In acute nonsepticemic pneumonic melioidosis, the most common radiographic pattern is similar, with alveolar infiltration and consolidation with or without cavitation
Pleural effusion or empyema is occasionally seen in acute stage.

Subacute:

Nonspecific patterns of pulmonary infiltration, including nodular, alveolar, or mixed infiltration/consolidation, with or without cavities

Chronic:

Mixed infiltration with cavities and fibronodular lesions associated with linear densities can be observed, which strongly mimics reactivation pulmonary tuberculosis.

Subclinical Form:

This type of presentation may be silent for many years, and infectious reactivation can present with one of the clinical forms when host resistance is compromised.

Treatment

Empiric anti-microbial coverage is generally recommended if there is suspicion of melioidosis, especially in the septicaemic form.

Conclusion

Melioidosis is becoming an increasingly global infection. Melioidosis can present with a wide spectrum of manifestations and can affect any part of the body. Radiological manifestations can be non-specific, resembling other conditions, both infective and non-infective diseases.

Dr. Shabna Jasmin K
Radiologist