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Two distinct types of Burkholderia pseudomallei, differentiated by the ability to assimilate L-arabinose but with similar morphologies and antigenicities, can be isolated from soil in Thailand. Approximately 25% of soil isolates from northeast Thailand were arabinose assimilators (Ara+), but in 1,200 sequentially studied patients, only arabinose "nonassimilators" (Ara-) caused melioidosis (P < 0.0001). In a murine model, there was a striking difference in virulence between Ara- and Ara+ B. pseudomallei. The mean (standard deviation) 50% lethal dose (LD[50]) inoculum for Ara- isolates was 182 (111) CFU/mouse compared with approximately 10(9) CFU/mouse for Ara+ soil isolates. There was no significant difference between the LD(50)s for clinical and soil Ara- isolates. All attempts to convert the biochemical phenotype by selective culture failed, which suggests that the biotype is stable.

Original publication




Journal article


Infection and immunity

Publication Date





4319 - 4321


Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.


Animals, Mice, Inbred BALB C, Humans, Mice, Burkholderia pseudomallei, Melioidosis, Arabinose, Bacterial Typing Techniques, Prospective Studies, Lethal Dose 50, Soil Microbiology, Phenotype, Thailand