Chlamydia pneumoniae present in the human synovium are viable and metabolically active

We demonstrated that chromosomal DNA from Chlamydia pneumoniae is present in synovial tissue in at least some patients with reactive arthritis/Reiter's syndrome and other arthritides. Here, we provide initial molecular evidence that the bacterium is viable and metabolically active when present in the synovium. We used reverse transcription-polymerase chain reaction (RT-PCR) assays targeting primary transcripts from the chlamydial rRNA operons, and mRNA from several C. pneumoniae genes (hsp60, ompA, KDO transferase, Mr=76000 protein), to analyse RNA preparations from synovial tissue of 10 patients with various forms of arthritis; each patient was known to be PCR-positive for C. pneumoniae DNA in synovium prior to RT-PCR assays. Two PCR-negative patients served as controls for RT-PCR assays. In the 10 patients PCR-positive for C. pneumoniae DNA, RT-PCR assays targeting primary transcripts from the rRNA operons of the organism showed that these molecules were present in each sample, as were transcripts from the bacterial hsp60 gene. Assays targeting mRNAs from the Mr=76000 protein and the KDO transferase genes of C. pneumoniae gave positive results for 6/10 preparations. We were unable to identify mRNA from the chlamydial major outer membrane protein gene (ompA) in any preparation. RNA preparations from the two control patients were negative in all RT-PCR assays targeting C. pneumoniae transcripts. These results indicate that in patients infected with the organism, synovial C. pneumoniae are viable and metabolically active, as are C. trachomatis cells in the same context. Such viability is consistent with a role in long-term contribution to pathogenesis in joint disease.