Q-fever, mol. karakterisering (WOT-01-002-005.05)

Coxiella burnetii (Cb) is an intracellular gram-negative bacterium that causes Q-fever in humans and animals. Two distinct virulence phases can be present; Phase 1 is virulent and has a complete LPS, phase 2 is not virulent and has a crippled LPS. Animals, especially cattle, sheep and goats, are the main source of Q fever infections in humans. The majority of infections in humans and animals runs asymptomatic, however, they do have different phenotypic expressions between the different species. In goats and to a lesser extent in ovine, abortion occurs as the main symptom. In cattle, infertility can occur while in humans mostly flu-like symptoms are seen possibly complicated by pneumonia, hepatitis and endometritis.

In this PhD project, we analyse the full genome sequences of various Dutch and foreign Coxiella burnetii isolates from goats, sheep, cattle and people, where the Cb isolates belong to different genotypes (MLVA types). We also investigate the influence of the phase 1 to 2 shift on virulence factors and possibly the genome stability.

A cell-free culturing method for Cb is setup. We also determined that the cell-free culture has no significant impact on virulence as measured in a mouse model. Adaptation of Cb to the various in vivo and in vitro models and transcriptomics studies of the bacterium indicate that the detected differences are mostly regulated primarily metabolic processes, rather than altered known virulence factors. Also, the switch from a virulent phase 1 into avirulent phase 2 has been examined and is found to have a genomic basis by which genes involved in O-antigen synthesis, are negatively regulated or even (partly) deleted from the genome. The genome sequencing of a large set of isolates and associated extrachromosomal elements (plasmids) is nearing completion and host-specific factors are still being pursued.