Demonstration of intracellular microorganisms (Rickettsia spp., Chlamydia pneumoniae, Bartonella spp.) in pathological human aortic valves by PCR.

OBJECTIVES

Rickettsiae, which causes vasculitis, has not been linked to atherosclerotic cardiovascular disease in contrast to Chlamydia pneumoniae whose association with coronary artery disease and with sclerotic heart valves in patients undergoing aortic valve replacement is well established, even if causality is yet to unproven. In the search for any of these infectious agents, 84 pathological and 15 normal aortic heart valves of patients undergoing forensic autopsy were analysed by PCR and DNA-sequencing.

METHODS

Two to four pieces of all valves were examined by semi-nested PCR, with primers specific for 16S rDNA, citrate synthase (gltA) and 17 kDa outer membrane protein (OMP) genes.

RESULTS

Genetic material from Rickettsia spp. and C. pneumoniae was found in 17 (20.2%) and 22 (26.2%), respectively, of the 84 pathological aortic valves. In 35 (41.7%) of these 84 valves either C. pneumoniae or Rickettsia spp. were detected by PCR and in six cases (7.1%) these two organisms co-existed. In one case with Lambl's excrescences, previously considered as aseptic, presence of rickettsia-like organisms also was demonstrated by light microscopy, immunohistochemistry and sequencing of the amplified PCR product showing 100% homology with the published sequence for R. helvetica. In three of the 15 control valves, genetic material from only C. pneumoniae was detected compared to Rickettsia spp. that was significantly detected only in the pathological valves (Fisher's Exact test, 1-sided p = 0.046).

CONCLUSIONS

The findings suggest that Rickettsia spp. also have a role in the pathogenesis of aortic valve disease.