Investigations

1st investigations to order

blood culture

Test
Result
Test

Melioidosis is only confirmed when B pseudomallei is cultured from a clinical sample.

All suspected cases require blood cultures.

Over 50% of all melioidosis cases have positive blood cultures.[8][70]

Result

positive for Burkholderia pseudomallei growth (or Burkholderia mallei)

sputum culture

Test
Result
Test

Positive in most cases of melioidosis community-acquired pneumonia. Culture rate improved with additional plating of sputum on selective media: Ashdown’s agar or, if not available, Burkholderia cepacia-selective agar (in cystic fibrosis clinics).[67][68][70]

Result

positive for B pseudomallei growth (or B mallei)

urine culture

Test
Result
Test

Positive in genitourinary melioidosis but also can be positive in melioidosis with systemic sepsis and/or community-acquired pneumonia. Culture of centrifuged deposit increases sensitivity.[69]

Result

positive for B pseudomallei growth (or B mallei)

culture of pus/swab from skin lesion, abscess, lymphadenitis, drained internal abscess (e.g., liver abscess)

Test
Result
Test

For swabs from open lesions, isolation rate is improved with additional plating of swab/pus on selective Ashdown's agar. If this is not available, use Burkholderia cepacia-selective agar (in cystic fibrosis clinics).[70]

Result

positive for B pseudomallei growth

chest x-ray

Test
Result
Test

Can be localised pneumonia or multi-lobar pneumonia in severe disease, or multiple lung abscesses in septic shock. Lung lesions in melioidosis tend to spare the apices.[7][72][73]

Result

features of pneumonia; lung abscesses

computer tomography (CT) abdomen and pelvis ± CT chest

Test
Result
Test

The kidneys, adrenal glands, and pericardium are sometimes involved.

Mycotic abdominal aortic and other artery aneurysms occasionally occur.[71][72] Mediastinal lymphadenopathy suggests aerosol exposure with inhalation.[8]

Result

internal abscesses common in spleen, liver, prostate

abdominal/pelvis ultrasound

Test
Result
Test

If CT is not available, and to avoid CT radiation dose in children and younger women, ultrasound of abdomen and pelvis is an alternative.

A ‘honeycomb’ appearance of the liver and multiple small, discrete abscesses in visceral organs (both liver and spleen) are suggestive of melioidosis.[71][72]

Result

'honeycomb' appearance (internal abscesses) in spleen and liver

Investigations to consider

throat swab in/on Ashdown's selective broth/agar

Test
Result
Test

May sometimes be the only positive sample. Sensitivity is approximately 80% compared with sputum.[66]B pseudomallei is never a commensal organism. Isolation from any clinical sample is diagnostic.

Result

positive for B pseudomallei growth

rectal swab in/on Ashdown's selective broth/agar

Test
Result
Test

Rarely the only sample that is positive.

Result

positive for B pseudomallei growth

cerebrospinal fluid (CSF) culture

Test
Result
Test

In cases of encephalomyelitis.[18]

Result

often negative (low bacterial numbers)

CSF microscopy, protein and glucose

Test
Result
Test

In cases of encephalomyelitis.[18]

Result

increased protein and white cells (often lymphocytes predominate)

polymerase chain reaction (PCR)

Test
Result
Test

Several PCR tests for melioidosis and glanders have been developed, the most useful of which targets TTS-1.[75] Whilst the positive predictive value is high they lack sensitivity, especially on blood, and so cannot be used to rule out infection.

Also important to identify an alternative cause (e.g., leptospirosis, dengue).

Result

may be positive

Emerging tests

rapid antigen detection test

Test
Result
Test

Currently under evaluation.[76][77][78]

As with PCR, the specificity and positive predictive value are high, but negative tests cannot rule out infection.

Result

may be positive

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