EComment. Mitral and aortic valve endocarditis caused by Streptococcus constellatus

Abstract

Concistre and colleagues reported their experience with the treatment of mitral and aortic valve infective endocarditis (IE) caused by Streptococcus constellatus [1]. I think there are some points that should be discussed. Nowadays, Staphylococci and Streptococci are the most common causative microorganisms for native valve IE. In contrast to Staphylococci, Streptococci are rarely resistant to penicillin G, which is recommended by modern guidelines for treatment of streptococcal IE in combination with gentamicin [2]. Other approved options for such cases are third generation cephalosporins – ceftriaxone, again with gentamicin. This regimen may be preferable due to a larger spectrum of activity, covering penicillin-resistant cocci. Furthermore, it is much more convenient for patients and personnel (injection of ceftriaxone once daily compared to six doses of penicillin G per day). The described patient stayed for a long time in the department of infective disease. Unfortunately, all periods of disease before admission to the cardiac surgery unit is like a “black box”: there is no information concerning predisposing factors, concomitant pathology, diagnostics and treatment provided etc. These data are essential in understanding the logic behind the initial antibiotic choice. Nevertheless with regards to the above-mentioned guidelines, in cases of native valve IE with unknown flora, initial antibiotics must cover most common pathogens, such as Staphylococci, Streptococci and Enterococci [2]. In light of this, the penicillin G-gentamicin combination seemed to be insufficient, especially in a patient who had been transferred from another ward and had previously received antibiotics. In our practice, we tend to start with a more reliable ceftriaxon + vancomycin regimen for empirical perioperative treatment of IE with unidentified etiology for such cases. After receiving microbiological data, including blood and tissue cultures, initial antibiotics regimen can be adjusted, if necessary. There is no doubt that the published case report is interesting owing to the rarity of S. constellatus as an etiological factor of IE. During our more than 10 years of surveillance at the Bakoulev Scientific Center for Cardiovascular Surgery (Moscow, Russia), where more than 4000 operations with cardiopulmonary bypass are performed annually, we have had only 5 consecutive blood cultures with S. constellatus (all in paediatric patients with non-IE pathology; all strains were susceptible to penicillin). There were no cases of S. constellatus isolation from intraoperatively resected valvular tissues in patients with IE. Returning back the present case, I suppose that if adequate anti-bacterial therapy had been started at an early stage, complications and subsequent requirement of surgery might have been avoided in this elderly patient.