Antimicrobial Activity ofAridicins, NovelGlycopeptide Antibiotics withHighandProlonged Levels inBlood

aridumhavea spectrum ofantimicrobial activity invitro whichissimilar tothatofvancomycin. Theantimicrobial activities ofthese glycopeptides against clinical bacterial isolates were compared withthose ofvancomycin andother related glycopeptide antibiotics invitro byagardilution andmicrotiter broth dilution tests andinvivoinmouse protection studies. Invitro they weresomewhat less effective than vancomycinagainst strains ofStaphylococcus aureusandless active against coagulase-negative Staphylococcus spp.However, they were more active than vancomycin against strains ofStreptococcus faecalis andmarkedly superior tovancomycin andother glycopeptide antibiotics against strains ofClostridium difficile. Inexperimental infections, aridicin A was effective against strains ofS.aureus,S.epidermidis, Streptococcus faecalis, andStreptococcus pyogenes, although its 50%effective doses werehigher thanthose ofvancomycin whenadministered after infection. After subcutaneous administration, aridicin A hada higher peaklevel inserum anda longer half-life than vancomycin orteicoplanin. Thearidicins were markedly superior tovancomycin whenadministered prior to infection inmouse protection tests, indicating long-acting potential. Aridicins areglycopeptide antibiotics ofthevancomycin class whichareproduced bya newgenusoftheorder Actinomycetales, Kibdelosporangiium aridum ATCC39922.