Culture results of heart valves resected from patients with active Enterococcus faecalis infective endocarditis undergoing heart valve surgery: insights into duration of antibiotic treatment required to achieve valve sterilisation.

PURPOSE: Heart valve culture results from patients with infective endocarditis (IE) provide insights into the antibiotic treatment duration required to achieve valve sterilisation. We aimed to assess the valve culture positivity rates of valves resected from patients with Enterococcus faecalis IE (EFIE).

METHODS

This was a national retrospective observational cohort study assessing adults with EFIE receiving valve surgery from 2004 to 2023 in Aotearoa New Zealand. We compared the valve culture result with the antibiotic treatment regimen and duration received before surgery.

RESULTS

One hundred and nine patients with EFIE met inclusion criteria. The valve culture positivity rate was 95% and 39% for valve samples obtained within 14 days or after 14 days of antibiotic treatment respectively. In addition to amoxicillin and/or benzylpenicillin, 40 patients received ceftriaxone and 38 received gentamicin as the sole pre-surgery synergistic antibiotic. There was no difference in valve culture positivity rates comparing the ceftriaxone and gentamicin synergistic antibiotic groups (P = 0.49).

CONCLUSION

Patients with EFIE who received valve surgery within 14 days of commencing antibiotic treatment had a very high valve culture positivity rate and this rate continued at moderate levels for those who received surgery after 14 days. We observed no difference in valve culture positivity rates when ceftriaxone or gentamicin was used as the sole pre-surgery synergistic antibiotic. The valve samples that remained culture positive after prolonged antibiotic treatment may help explain the higher relapse rate of patients with EFIE who do not receive valve surgery when compared with patients with other causes of IE.