Retapamulin -: Pleuromutilin antibiotic

Due to the emergence of multidrug-resistant microorganisms, research efforts are focusing on new classes of antibacterials with different mechanisms of action from those in clinical use. One such agent is retapamulin, a pleuromutilin derivative with a unique mechanism of action. Currently under development for the topical treatment of skin infections, retapamulin has shown no target-specific cross-resistance to commonly used antibiotics. In a number of in vitro studies, retapamulin demonstrated activity that was equivalent or superior to other common antibiotics against clinical isolates from skin and skin structure infections. The organisms susceptible to retapamulin include: Streptococcus pyogenes, Streptococcus agalactiae, beta-hemolytic streptococci, viridans streptococci, Staphylococcus aureus, coagulase-negative staphylococci (including Staphylococcus epidermidis), Propionibacterium spp. (including Propionibacterium acnes), Prevotella spp., Porphyromonas spp. and Fusobacterium spp. However, retapamulin showed minimal or no activity against enterococci and Gram-negative bacilli. Importantly, retapamulin maintains its activity against organisms that are resistant to a number of antimicrobial agents, including methicillin, erythromycin, fusidic acid, mupirocin, azithromycin and levofloxacin. Evidence from multiple-step and single-step studies also suggests that retapamulin has a low potential to select for resistant mutants in S. pyogenes and S. aureus.