Analysis of the O-antigen biosynthesis regions of phase II isolates of Coxiella burnetii.

The O-antigen-encoding region in the genomes of 14 isolates of Coxiella burnetii was examined by PCR. Five phase I isolates (Nine Mile clone 7, KAV, Ohio, Henzerling RSA 343, Q173) were analyzed and no deletions were detected. Two other isolates of unknown phase (Scottish, WAV) were examined, but no deletions were detected. In contrast, RSA 514 and three phase II isolates (Nine Mile phase II clone 4, Nine Mile phase II clone 1, Nine Mile Baca) contained large deletions, and the latter two were further characterized by DNA sequencing. Three other phase II isolates (Henzerling RSA 331, M44, Australian QD) contained no apparent deletions. Reactivity to phase I- and phase II-specific antibodies by immunofluorescence assay was used to further characterize isolates. Selected ORFs in Australian QD and M44 DNA were sequenced to detect mutations, and no significant changes were found. Australian QD RNA was examined by reverse transcriptase-PCR specific to the four ORFs hypothesized to encode the O-antigen sugar virenose, which this isolate has been shown to lack, as well as one that is predicted to encode part of the O-antigen ABC transporter. Each of these five genes was found to be expressed.