Molecular Frequency of Coxiella burnetii, Tropheryma whipplei, Brucella, and Bartonella in Heart Valve Tissues from Patients with Infective Endocarditis: A Cross-Sectional Study from Tehran, Iran

Background Infective endocarditis (IE) is a life-threatening condition caused by diverse microbial agents and remains a major diagnostic and therapeutic challenge, particularly in cases of blood culture–negative IE (BCN-IE). Methods In this cross-sectional study, 405 formalin-fixed paraffin-embedded heart valve tissue samples from 232 patients with pathologically and clinically confirmed IE who underwent valve replacement were collected between March 2021 and March 2025 from two tertiary referral hospitals in Tehran, Iran. Following DNA extraction, Coxiella burnetii , Brucella spp., and Bartonella spp. were detected using TaqMan real-time PCR, while Tropheryma whipplei was identified by SYBR Green real-time PCR. Species-level identification of Brucella and Bartonella in positive samples was performed using conventional and multiplex real-time PCR. Results Overall, C. burnetii , Brucella spp., Bartonella spp., and T. whipplei were detected in 6.9%, 8.6%, 5.6%, and 3.0% of patients, respectively. The study population comprised 156 males (67.2%) and 76 females (32.8%), with a mean age of 47 years. The aortic (40.3%) and mitral (39.1%) valves were the most frequently involved sites. Bartonella quintana , Brucella melitensis , and Brucella abortus were identified among positive samples. Dyspnea was significantly associated with C. burnetii (P=0.02), Bartonella (P=0.04), and Brucella infections (P=0.009), while fever (P=0.03) and sweating (P=0.001) were significantly associated with Brucella infection. Conclusions Fastidious and intracellular pathogens are important but overlooked causes of BCN-IE in Iran. Molecular analysis of heart valve tissues represents a valuable diagnostic strategy and supports the need for improved surveillance, prevention, and targeted management of zoonotic and fastidious agents in IE.