In Vitro Activity of Rifampin, Rifabutin, and Rifapentine against Enterococci and Streptococci from Periprosthetic Joint Infection

After staphylococci, streptococci and enterococci are the most frequent causes of periprosthetic joint infection (PJI). MICs and minimum biofilm bactericidal concentrations of rifampin, rifabutin, and rifapentine were determined for 67 enterococ-cal and 59 streptococcal PJI isolates. Eighty-eight isolates had rifampin MICs of ≤1 µg/ ml, among which rifabutin and rifapentine MICs were ≤ 8 and ≤ 4 µg/ml, respectively. There was low rifamycin in vitro antibiofilm activity except for a subset of Streptococcus mitis group isolates. IMPORTANCE Rifampin is an antibiotic with antistaphylococcal biofilm activity used in the management of staphylococcal periprosthetic joint infection with irrigation and debridement with component retention; some patients are unable to receive rifampin due to drug interactions or intolerance. We recently showed rifabutin and rifa-pentine to have in vitro activity against planktonic and biofilm states of rifampin-sus-ceptible periprosthetic joint infection-associated staphylococci. After staphylococci, streptococci and enterococci combined are the most common causes of peripros-thetic joint infection. Here, we investigated the in vitro antibiofilm activity of rifampin, rifabutin, and rifapentine against 126 Streptococcus and Enterococcus periprosthetic joint infection isolates. In contrast to our prior findings with staphylococcal biofilms, there was low antibiofilm activity of rifampin, rifabutin, and rifapentine against PJI-associated streptococci and enterococci, apart from some Streptococcus mitis group isolates.