Latent Q fever endocarditis in patients undergoing routine valve surgery

Abstract

Background and aim of the study: Q fever is a worldwide zoonosis caused by a fastidious bacterium, Coxiella burnetii. A recent major outbreak of which in the Netherlands will most likely lead to the emergence of hundreds of cases of C. burnetii endocarditis during the next decade. Patients undergoing cardiac valve surgery may carry undiagnosed Q fever endocarditis with possible disastrous outcomes, and hence may benefit from a screening strategy. The study aim was to evaluate the frequency of unsuspected latent Q fever endocarditis in patients undergoing routine valve surgery.

Methods: At the present authors' institution, all resected cardiac valves/prostheses are examined routinely histologically, microbiologically and on a molecular biological basis, in addition to serological testing for fastidious microorganisms. A retrospective review was conducted of data relating to all patients who had unsuspected Q fever endocarditis that had been diagnosed after routine valve/prosthesis replacement/repair between 2000 and 2013 at the authors' institution.

Results: Among 6,401 patients undergoing valve surgery, postoperative examinations of the explanted valves/prostheses led to an unexpected diagnosis of Q fever endocarditis in 14 cases (0.2%), who subsequently underwent appropriate medical treatments. Only two of the patients (14%) had intraoperative findings suggestive of endocarditis. On serological analysis of the blood samples, 11 patients (79%) presented an evocative Phase I IgG antibody titer > or =800. Valvular tissue-sample analyses yielded positive cultures and PCR in the same 13 patients (93%), whereas pathological and immunohistochemical examinations alone were suggestive of endocarditis in only seven Cases (50%).

Conclusion: This screening strategy led to an unexpected diagnosis of Q fever endocarditis in 0.2% of patients undergoing routine valve surgery, who received subsequent appropriate antibiotic therapy. Systematic serological analysis should be mandatory before performing heart valve surgery in countries where C. burnetii is endemic. A positive serology should lead to appropriate valve-specimen analyses, including microbiological, molecular biological and histological evaluations.