Passive transfer of OMV-immune sera protects mice against septicemic melioidosis. Naive BALB/c mice (n = 5 per group) were treated with OMV-immune sera, were treated with control sera, or were left untreated and were challenged 1 h later with 5 × 105 CFU of B. pseudomallei strain K96243 by i.p. inoculation. Two independent experiments were performed, and survival was monitored for 14 days. **, P < 0.01, compared with control mice using a log-rank Mantel-Cox survival analysis.