Bacteraemia caused by non-faecalis and non-faecium Enterococcus species—a retrospective study of incidence, focus of infection, and prognosis

Background/aim: Enterococcus faecalis and Enterococcus faecium cause human infections including bacteraemia and infective endocarditis (IE). Only few studies describing non-faecalis and non-faecium Enterococcus (NFE) infections have been conducted. We aimed to describe the incidence, prognosis, and focus of infection of bacteraemia with NFE. Methods: This retrospective population-based study included all episodes of patients having a blood culture with growth of NFE between 2012 and 2019 in Region Skåne, Sweden. Information was collected from medical records. Episodes of bacteraemia caused by NFE were compared to episodes of bacteraemia caused by E. faecalis and E. faecium. Results: During the study period, 136 episodes with NFE bacteraemia were identified corresponding to an incidence of NFE bacteraemia of 16 cases per 1,000,000 person-years among adults. Enterococcus casseliflavus (n=45), Enterococcus gallinarum (n=34), and Enterococcus avium (n=29) were the most common species. The most common foci of infection were biliary tract infections (n=17) followed by gastrointestinal infections (n=7). Urinary tract infections were not commonly caused by NFE (n=1), and no episodes of IE were caused by NFE. Polymicrobial bacteraemia was more common with NFE (73%) than with E. faecalis (35%) and E. faecium (42%). Community acquired infections were more common in bacteraemia with NFE compared to E. faecium. 30- and 90-day survival rates were 76% and 68%, respectively, and recurrent NFE bacteraemia was seen after 3% of the episodes. Conclusion: Bacteraemia caused by NFE is rare and is often polymicrobial. Biliary tract focus is common in NFE bacteraemia whereas IE and urinary tract focus are uncommon.