Objectives: Akacid plus Ò is a new member of the polymeric guanidine family of disinfectants. It was especially developed to enhance the antimicrobial activity of this class with significantly less toxicity. The in vitro activity of Akacid plus Ò compared with chlorhexidine digluconate and mupirocin was tested against a total of 369 recent clinical isolates. Methods: The organisms tested by CLSI reference methods included the following: Staphylococcus aureus (98), Staphylococcus epidermidis (9)

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... , , Stenotrophomonas maltophilia (4), Candida spp. (10) and Aspergillus spp. (7) . In vitro selection of resistance to Akacid plus Ò was carried out on 24 strains. Toxicological analyses were also performed. Results: All tested agents were more effective against Staphylococcus spp. and Bacillus spp. than against E. faecalis and Gram-negative bacteria. The MIC 90 s of chlorhexidine and mupirocin showed a 4-fold and 32-fold increase for methicillin-resistant S. aureus in comparison with methicillin-susceptible strains, while MIC values of Akacid plus Ò were similar for antibiotic-susceptible and multiresistant strains. Bactericidal action of Akacid plus Ò was observed at 1-2· MIC. The in vitro selection of resistance test showed no increase in MIC values of Akacid plus Ò for any isolate after 30 passages. In addition, Akacid plus Ò showed low oral and dermal toxicity. Conclusions: These preliminary results demonstrate the broad antimicrobial properties of Akacid plus Ò , which makes it a promising tool for topical application in the prophylaxis and treatment of bacterial and fungal infections.