Infective endocarditis: etiology and role of contemporary methods in establishing the microbiological diagnosis

Aim

To study the etiology of infective endocarditis (IE) over 5 years in general municipal hospital and to define the diagnostic significance of molecular microbiological methods.

Material and methods

We recruited 125 patients (median age 50 years, 77 male) with definite IE (DUKE 2009), hospitalized in 2010-2015 to the city clinical hospital. Etiology of IE was studied with standard method in all patients and with PCR or PCR with DNА sequencing in 61 (48.8%) patients.

Results

Primary IE was diagnosed in 70 (56%) cases. Seventy three (58.4%) patients had positive blood cultures, represented primarily by Staphylococcus spp. (n = 42, 57.5%), Enterococcus spp. (n = 9, 12.3%), non-НАСЕК group (n = 4, 5.5%) and Streptococcus spp. (n = 3, 4.1%). Molecular microbiological blood tests were performed in 61 patients; 30 (49.2%) of them had positive blood cultures, and 42 (68.9%) had positive PCR, including 16 cases of culturenegative IE. The results of two methods were discordant in 7 (11.5%) patients: different infectious agents were detected in 3 cases (Enterococcus spp. in blood cultures, with Staphylococcus spp., Streptococcus spp., E. coli DNA diagnosed by PCR), and 4 patients had false-negative PCR.

Conclusion

Etiology of contemporary IE is represented mainly by staphylococcal and enterococcal bacteria, while streptococcal IE is rare. The infectious agent could be detected in venous blood samples by traditional diagnostic method in 58.4% of patients, by PCR in 68.9% and by combination of two methods in 71.2%.

Key words

Infective endocarditis, bacteriological diagnostic methods, polymerase chain reaction, molecular microbiological methods, Staphylococcus aureus.