Activities of four frog skin-derived antimicrobial peptides (temporin-1DRa, temporin-1Va and the melittin-related peptides AR-23 and RV-23) against anaerobic bacteria

The activities of two antimicrobial peptides belonging to the temporin family (temporin-1DRa from Rana draytonii and temporin-1Va from Rana virgatipes) and two peptides with structural similarity to the bee venom peptide melittin (AR-23 from Rana tagoi and RV-23 from R. draytonii) were evaluated against a range of reference strains and clinical isolates of anaerobic bacteria. These peptides were selected because they show broad-spectrum growth inhibitory activity against reference strains of several medically important aerobic microorganisms and against clinical isolates of methicillin-resistant Staphylococcus aureus. All peptides showed relatively high potency (minimum inhibitory concentration (MIC) ≤25 μM) against the Gram-positive bacilli Propionibacterium acnes and Clostridium tertium and the Gram-positive cocci Peptostreptococcus anaerobius. Activity was lower and more variable against Clostridium septicum, Clostridium perfringens and Peptostreptococcus asaccharolyticus. Growth of the Gram-negative bacilli Bacteroides fragilis and Fusobacterium spp. was poorly inhibited, but all the peptides were active (MIC ≤ 25 μM) against Prevotella melaninogenica. The clinical utility of the melittin-related peptides is limited by their toxicities, but temporin-1DRa and temporin-1Va have relatively low haemolytic activity against human erythrocytes and so represent candidates for drug development, particularly for topical therapy of infected surface lesions.