Differentials
Tuberculosis
SIGNS / SYMPTOMS
Patients with chronic pulmonary melioidosis are often misdiagnosed as 'smear-negative' tuberculosis.[64]
Both infections are more common in diabetics.
Patients are often less systemically unwell than those with chronic pulmonary melioidosis.
INVESTIGATIONS
Sputum cultures with acid-fast bacilli stains: positive.
A cavity on the chest x-ray may be observed, but it is difficult to distinguish the diseases radiologically; apices more often affected.
Pneumonia
SIGNS / SYMPTOMS
No specific differentiating signs or symptoms.
Failure to respond to the usual empirical antibiotic regimens may be suggestive of melioidosis.
INVESTIGATIONS
Cultures of blood, sputum, urine, and pus: positive for other common bacteria such as Streptococcus pneumoniae, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Salmonella typhi.
Klebsiella pneumoniae and other gram-negative organisms may be an issue in some regions (e.g., Southeast Asia).
Sepsis
SIGNS / SYMPTOMS
No specific differentiating signs or symptoms.
Failure to respond to the usual empirical antibiotic regimens may be suggestive of melioidosis.
INVESTIGATIONS
Cultures of blood, sputum, urine, and pus: positive for other common bacteria such as Streptococcus pneumoniae, Staphylococcus aureus, Escherichia coli, Pseudomonas aeruginosa, and Salmonella typhi.
Klebsiella pneumoniae and other gram-negative organisms may be an issue in some regions (e.g., Southeast Asia).
Leptospirosis
SIGNS / SYMPTOMS
No specific differentiating signs or symptoms.
Regional knowledge of melioidosis-endemic regions can help in returned travellers.
Very occasionally a patient can have two 'tropical infections' concurrently.[62]
INVESTIGATIONS
Serology (microscopic agglutination test): positive for leptospirosis.
Polymerase chain reaction (PCR): positive for leptospirosis.
Dengue fever
SIGNS / SYMPTOMS
No specific differentiating signs or symptoms.
Regional knowledge of melioidosis-endemic regions can help in returned travellers.
Very occasionally a patient can have two 'tropical infections' concurrently.[62]
INVESTIGATIONS
Leukopenia and thrombocytopenia are common, but may also occur in overwhelming septicaemic melioidosis.
Serum PCR: positive for dengue virus early in the illness.
Rapid diagnostic test for NS-1 antigen has good sensitivity. IgM has good sensitivity but some assays show poor specificity.
Isolation of virus by tissue culture is less common.
Malaria
SIGNS / SYMPTOMS
No specific differentiating signs or symptoms.
Regional knowledge of melioidosis-endemic regions can help in returned travellers.
Very occasionally a patient can have two 'tropical infections' concurrently.[62]
INVESTIGATIONS
Giemsa-stained thick and thin blood smears: positive for Plasmodium species.
Rapid diagnostic tests: positive for Plasmodium species.
Rickettsial infections (including scrub typhus)
SIGNS / SYMPTOMS
No specific differentiating signs or symptoms.
Regional knowledge of melioidosis-endemic regions can help in returned travellers.
Very occasionally a patient can have two 'tropical infections' concurrently.[62]
INVESTIGATIONS
Possible leukopenia and/or abnormal liver function tests.
Positive serology, but results will not be available in real time.
Amoebiasis
SIGNS / SYMPTOMS
Signs of sepsis are less prominent.
INVESTIGATIONS
Abdominal/pelvic ultrasound: homogeneous hypo-echoic round or oval lesion.
Computed tomography abdomen/pelvis: rounded, well-defined, low-attenuation lesion; wall commonly enhances with contrast.
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