New insights on the antibacterial efficacy of miconazole in vitro
Miconazole is a broad‐spectrum antifungal used in topical preparations. In the present investigation the minimal inhibitory concentration (MIC) of miconazole for eighty wild type strains of gram‐positive and gram‐negative bacteria isolated from infected skin lesions was assessed using a modified agar dilution test (adapted to CLSI, Clinical Laboratory Standards Institute). 14 ATCC reference strains served as controls. Miconazole was found efficacious against gram‐positive aerobic bacteria (n=62 species), the MICs against Staphylococcus (S.) aureus, S. spp., Streptococcus spp. und Enterococcus spp. ranged between 0.78 and 6.25 μg/mL. Interestingly, there were no differences in susceptibility between methicillin‐susceptible (MSSA, 3) methicillin‐resistant (MRSA, 6) and fusidic acid‐resistant (FRSA, 2) S. aureus isolates. Strains of Streptococcus pyogenes (A‐streptococci) (8) were found to be slightly more sensitive (0.78‐1.563 μg/mL), while for gram‐negative bacteria, no efficacy was found within the concentrations tested (MIC >200 μg/mL). In conclusion, for the gram‐positive aerobic bacteria the MICs of miconazole were found within a range which is much lower than the concentration of miconazole used in topical preparations (2%). Thus topically applied miconazole might be a therapeutic option in skin infections especially caused by gram‐positive bacteria even by those strains which are resistant to antibiotics.
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