Calcium Sulphate Mixed with Antibiotics Does Not Decrease Efficacy Against Cutibacterium Acnes (formerly Propionibacterium Acnes), in Vitro Study.

BACKGROUND:This study explored the in vitro efficacy of antibiotics mixed with calcium sulfate (ACS) against Cutibacterium acnes (C. acnes). METHODS:C. acnes isolates from orthopaedic infection sites were tested for antimicrobial susceptibility with ACS. Minimal inhibitory concentrations (MIC) were determined with a gradient diffusion method (Etest® strips). RESULTS:When tested with Etest®, all 22 isolates were susceptible to penicillin, ceftriaxone, vancomycin, and two were resistant to clindamycin (MICs of 4 and 8 mg/L). Penicillin and rifampin had the largest inhibition zone diameters. CONCLUSIONS:Antibiotics retained activity against C. acnes when mixed with calcium sulfate.