Melioidosis of the Central Nervous System: Impact of the bimA_Bm Allele on Patient Presentation and Outcome

Background. The autotransporter protein Burkholderia intracellular motility A (BimA) facilitates the entry of Burkholderia pseudomallei into the central nervous system (CNS) in mouse models of melioidosis. Its role in the pathogenesis of human cases of CNS melioidosis is incompletely defined.Methods. Consecutive culture-confirmed cases of melioidosis at 2 sites in tropical Australia after 1989 were reviewed. Demographic, clinical, and radiological data of the patients with CNS melioidosis were recorded. The bimA allele (bimA(Bm) or bimA(Bp)) of the B. pseudomallei isolated from each patient was determined.Results. Of the 1587 cases diagnosed at the 2 sites during the study period, 52 (3.3%) had confirmed CNS melioidosis: 20 (38.5%) had a brain abscess, 18 (34.6%) had encephalomyelitis, 4 (7.7%) had isolated meningitis, and 10 (19.2%) had extra-meningeal disease. Among the 52 patients, there were 8 (15.4%) deaths; 17/44 (38.6%) survivors had residual disability. The bimA allele was characterized in 47/52; 17/47 (36.2%) had the bimA(Bm) allele and 30 (63.8%) had the bimA(Bp) allele. Patients with a bimA(Bm) variant were more likely to have a predominantly neurological presentation (odds ratio [OR]: 5.60; 95% confidence interval: 1.52-20.61; P = .01), to have brainstem involvement (OR: 7.33; 1.92-27.95; P = .004), and to have encephalomyelitis (OR: 4.69; 1.30-16.95; P = .02). Patients with a bimA(Bm) variant were more likely to die or have residual disability (OR: 4.88; 1.28-18.57; P = .01).Conclusions. The bimA allele of B. pseudomallei has a significant impact on the clinical presentation and outcome of patients with CNS melioidosis.