Corallopyronin A (CorA) is an antibiotic produced by Corallococcus coralloides. CorA effectively targets bacterial RNA polymerase and has shown activity against Gram-positive bacteria, including MRSA. Since CorA has a different mode of action from the rifamycin class, it is effective against rifampicin-resistant S. aureus. Because S. aureus is a major contributor to periprosthetic joint infections (~60%) (PJIs), CorA has the potential to be a promising therapeutic option for treating these infections.

The study aims to further understand the antimicrobial potential of CorA against S. aureus and coagulase-negative staphylococci (CNS), including strains from prosthesis infections and stable Small Colony Variants (SCV). The minimum inhibitory concentrations (MICs) of CorA were determined for 45 S. aureus and 15 coagulase-negative staphylococci (CNS), showing promising results with MICs ranging from 0.125 mg/l to 1 mg/l. In addition, time-kill curves in the presence of 4 x MIC performed with 5 different S. aureus strains showed a significant decrease of 1.5-3 Log10 cfu mL-1 of viable cells within 25h. Minimum bactericidal concentration (MBC) tests were conducted for 29 strains S. aureus by checking the survival rates in the MIC determination. MBC results demonstrated that CorA was bactericidal against 80% of tested CNS strains and 37% S. aureus strains. The results of this study provide robust evidence of CorA efficiency against S. aureus lab strains, clinical isolates, SCVs and CNS.