Monaldi Hospital Study Reveals Microbiota Differences in Endocarditis Patients

Researchers in Italy have revealed notable differences in gut, oral, and skin microbiota among patients with heart valve disease who have infective endocarditis compared to those without the infection, according to a study published in the journal Microbiology Spectrum.

Prospective Pilot Study Examines Microbiota in Heart Valve Patients

Infective endocarditis is classified as a serious infection of the endocardium that is associated with substantial morbidity and mortality. While the condition can be caused by bacteria normally found in the mouth, gut, and skin, relatively little has been known about the broader relationship between host microbiota and infective endocarditis. Previous research largely concentrated on oral microbiota, leaving other microbial communities underexplored.

To investigate further, researchers conducted a prospective observational pilot study involving 36 patients awaiting heart valve replacement at Monaldi Hospital in Naples between November 2021 and December 2022. Among the participants, 25 presented with definite infective endocarditis and positive blood cultures, while 11 served as controls with non-infective valve disease requiring surgery.

Microbial Diversity and Dysbiotic Features

Prior to undergoing surgery, faecal, oral, and skin samples were collected from the participants. The composition of their microbiota was assessed using 16S ribosomal RNA amplicon sequencing, as detailed in data from National Center for Biotechnology Information records.

According to the findings, patients with infective endocarditis displayed lower microbial diversity in oral and skin samples compared with the control group. However, no difference in diversity was identified in the gut. Furthermore, skin microbial composition differed significantly between the two cohorts when assessed using unweighted UniFrac analysis.

Cases and controls were generally similar, except for higher inflammatory markers and a higher prevalence of prosthetic valves observed in the infective endocarditis cases. Causative pathogens identified in the cases included Staphylococcus species, Streptococcus species, and Enterococcus species. The concordance between bacterial changes and blood isolates was low, suggesting that dysbiosis might be potentially associated with infective endocarditis risk rather than acting as a direct reservoir of specific pathogens.

Impact of Antibiotic Exposure and Next Steps

The investigation noted that antibiotic exposure complicated the interpretation of the microbiota findings. Out of the 25 patients with infective endocarditis, six were enrolled before receiving antibiotics, whereas 19 had already received antibiotics for a median of five days.

When comparing patients who had received no antibiotics with those treated for more than three days, researchers observed certain microbiota differences in both treated and untreated patients, while other variations were identified solely among those who had received antibiotics. Differences involving oral Neisseria and several gut bacterial groups, including Bacteroides, were observed irrespective of antibiotic exposure, whereas other oral and gut changes appeared only in antibiotic-treated patients.

Ultimately, the researchers concluded that patients with heart valve disease and infective endocarditis exhibited dysbiotic features across their oral, gut, and skin microbiota. Nevertheless, the study authors cautioned that these exploratory findings cannot establish a definitive pathogenetic role for dysbiosis and should be regarded as hypothesis-generating. They added that larger longitudinal studies, including antibiotic-naive patients where feasible, are necessary to validate the results, clarify the effects of antibiotic exposure, and investigate potential pathogenetic mechanisms.