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Over a 34-mo period we studied 51 patients with Q fever and 102 control subjects (with various lower-respiratory-tract infections) who were matched for age, sex, and time of onset of infection. By univariate analysis (not adjusted for multiple comparisons), cases differed significantly from controls in the following activities: working on a farm; slaughtering or dressing animals; and contact with cats, cattle, and sheep. The strongest association was with exposure to stillborn kittens--11 of 51 cases vs. none of 102 controls (P less than .00000)--and with exposure to parturient cats (odds ratio, 10.3; 95% confidence interval, 3.5-31.8). Exposures to newborn animals (chiefly kittens) and stillborn kittens were significant risk factors by multivariate analysis, as were rural residence and slaughtering or dressing animals. In 13 Q fever incidents following exposure to parturient cats, 80 people became ill, 52 of whom had serological evidence of recent Coxiella burnetii infection (most of the others were not tested).

A whole-body mouse model of pneumonic melioidosis was established for future evaluation of biodefense vaccine candidates. The aerosol 50% lethal doses of Burkholderia pseudomallei strain 1026b for BALB/c and C57BL/6 mice and the times to death, dissemination in organs, and tissue loads after exposure of the mice to low-and high-dose aerosols are reported. In addition, rpsL mutant backgrounds were attenuated in this acute model of disease.

Burkholderia pseudomallei, the etiologic agent of melioidosis, is a gram-negative facultative intracellular bacterium. This bacterium is endemic in Southeast Asia and Northern Australia and can infect humans and animals by several routes. It has also been estimated to present a considerable risk as a potential biothreat agent. There are currently no effective vaccines for B. pseudomallei, and antibiotic treatment can be hampered by nonspecific symptomology, the high incidence of naturally occurring antibiotic resistant strains, and disease chronicity. Accordingly, there is a concerted effort to better characterize B. pseudomallei and its associated disease. Before novel vaccines and therapeutics can be tested in vivo, a well characterized animal model is essential. Previous work has indicated that mice may be a useful animal model. In order to develop standardized animal models of melioidosis, different strains of bacteria must be isolated, propagated, and characterized. Using a murine intraperitoneal (IP) infection model, we tested the virulence of 11 B. pseudomallei strains. The IP route offers a reproducible way to rank virulence that can be readily reproduced by other laboratories. This infection route is also useful in distinguishing significant differences in strain virulence that may be masked by the exquisite susceptibility associated with other routes of infection (e.g., inhalational). Additionally, there were several pathologic lesions observed in mice following IP infection. These included varisized abscesses in the spleen, liver, and haired skin. This model indicated that commonly used laboratory strains of B. pseudomallei (i.e., K96243 and 1026b) were significantly less virulent as compared to more recently acquired clinical isolates. Additionally, we characterized in vitro strain-associated differences in virulence for macrophages and described a potential inverse relationship between virulence in the IP mouse model of some strains and in the macrophage phagocytosis assay. Strains which were more virulent for mice (e.g., HBPU10304a) were often less virulent in the macrophage assays, as determined by several parameters such as intracellular bacterial replication and host cell cytotoxicity.

Burkholderia mallei, a category B biothreat agent, is a facultative intracellular pathogen that causes the zoonotic disease glanders. The B. mallei VirAG two-component regulatory system activates the transcription of ϳ60 genes, including a large virulence gene cluster encoding a type VI secretion system (T6SS). The B. mallei tssM gene encodes a putative ubiquitin-specific protease that is physically linked to, and transcriptionally coregulated with, the T6SS gene cluster. Mass spectrometry and immunoblot analysis demonstrated that TssM was secreted in a virAG-dependent manner in vitro. Surprisingly, the T6SS was found to be dispensable for the secretion of TssM. The C-terminal half of TssM, which contains Cys and His box motifs conserved in eukaryotic deubiquitinases, was purified and biochemically characterized. Recombinant TssM hydrolyzed multiple ubiquitinated substrates and the cysteine at position 102 was critical for enzymatic activity. The tssM gene was expressed within 1 h after uptake of B. mallei into RAW 264.7 murine macrophages, suggesting that the TssM deubiquitinase is produced in this intracellular niche. Although the physiological substrate(s) is currently unknown, the TssM deubiquitinase may provide B. mallei a selective advantage in the intracellular environment during infection.

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Abstract. Thirty-one female Syrian hamsters (Mesocricetus auratus) were inoculated intraperitoneally with a lethal dose of Burkholderia mallei (Budapest strain). Hamsters were killed postinoculation on days 0 through 6. Lesions were first noted in the spleens on postinoculation day 1, and in mediastinal and mesenteric lymph nodes, mediastinum, liver, and bone marrow on day 2. Lesions were present in the lung and submandibular lymph nodes on day 3, and in the brain on day 5. The characteristic histopathologic change was necrotizing pyogranulomatous inflammation, often with hemorrhage. Lesions indicative of impaired vascular perfusion, such as ischemia and infarction, were evident at the later time points. Pathologic changes generally increased in severity and distribution with time, and almost all tissues were ultimately affected. Our findings suggest that intraperitoneal bacteria were rapidly transported to mediastinal lymph nodes by transdiaphragmatic lymphatics and ultimately seeded other tissues hematogenously. The results of the study indicate that the Syrian hamster is a useful small animal model for glanders.