Laboratory diagnosis of melioidosis

Melioidosis is a serious infection caused by the soil dwelling Gram-negative bacillus Burkholderia pseudomallei. This disease is most commonly reported in north-east Thailand and the top end of northern Australia where it is considered endemic. The most frequent picture is a septicaemic illness often in association with bacterial dissemination to distant sites, but possible manifestations are extremely broad ranging. Isolation of B. pseudomallei represents the diagnostic "gold standard". Gram stain and microscopy of clinical specimens has poor sensitivity, and the bacterial appearance is not specific. Culture is straightforward, although sensitivity can be increased by the use of selective media for non-sterile specimens and enrichment media for sterile site samples. Serological tests have poor diagnostic accuracy in melioidosis-endemic areas where seropositivity is common in the healthy population, but are more useful in the non-endemic setting. Use of molecular techniques to identify the presence of B. pseudomallei in clinical specimens has been described, but is not routine in most diagnostic microbiology laboratories.