Causative Microorganisms in Infective Endocarditis: Prospective Data from the Iranian Registry of Infective Endocarditis (IRIE)

Background: Infective Endocarditis (IE) is a life-threatening disease. Regardless of improved healthcare, the incidence of IE has increased over time. A variety of microorganisms have been found to be associated with IE. Objectives: This study aimed to determine the incidence of various microorganisms in patients admitted with IE and to assess their relationships with in-hospital complications. Methods: This prospective cross-sectional study was conducted on patients with definite or possible IE based on the Duke criteria at a tertiary referral center between 2016 and 2021. Blood cultures were performed for all the patients to document the positive or negative blood cultures as well as the types of microorganism. Statistical analyses were performed using the SPSS 18 software. Results: The study population consisted of 286 patients (181 males (63.3%) and 105 females (36.7%)) with the mean age of 49.67 +/- 17.11 years. The most common cardiac predisposing factor was the prosthetic valve (n = 110, 38.5%) followed by a history of congenital heart disease (n = 68, 23.8%), while the most frequent non-cardiac predisposing factors were a history of chronic kidney disease (n = 75, 26.2%) and diabetes mellitus (n = 53, 18.5%). The most frequent causative microorganisms were coagulase-negative Staphylococcus (n = 37, 12.9%), Staphylococcus aureus (n = 31, 10.4%), Enterococcus (n = 29, 10.1%), and Streptococcus viridans (n = 14, 4.9%). The most common complications were acute renal failure (26.6%), heart failure (17.5%), and pulmonary involvement (8.4%). Conclusions: The frequencies of microorganisms related to IE, especially culture-negative IE, vary in different countries, precluding the practical use of a specific guideline around the world. Further research is, therefore, required to determine the epidemiology and microbiology of IE in different countries with a view to eventually devising an individualized guideline appropriate to the epidemiology and microbiology of IE in every country.