In vitro antimicrobial activity of miconazole and polymyxin B against canine meticillin‐resistant Staphylococcus aureus and meticillin‐resistant Staphylococcus pseudintermedius isolates
Hypothesis/Objectives – The main aim of the present study was to investigate the in vitro antimicrobial activity of miconazole, polymyxin B and a combination of both against 24 canine MRSA and 50 canine MRSP isolates. The minimal inhibitory concentration (MIC) values of 12 other antimicrobial agents were also determined.
Methods – All MIC values were determined according to a broth microdilution assay.
Results – Acquired resistance was found to all tested agents, except for linezolid, miconazole and polymyxin B. The MIC values for miconazole and polymyxin B against MRSA were in the range of 4–8 and 8–64 μg/mL, respectively, while the MIC values for miconazole and polymyxin B against MRSP were in the range of 1–2 and 0.25–4 μg/mL, respectively. Using a combination of miconazole and polymyxin B, there was no evidence for enhanced in vitro activity of the combination (i.e. synergy) of both products. Nevertheless, MIC90 values of the combination of these antimicrobial agents and of a commercial product containing both agents were at least 1000 times lower than the concentration present in the commercial product.
Conclusions and clinical importance – These results indicate that the topical use of a combination of miconazole and polymyxin B in a 43.5:1 ratio may have potential for the treatment of MRSA‐mediated and MRSP‐associated otitis externa in dogs.
Document Type: Research Article
Affiliations: 1: Department of Pathology, Bacteriology and Avian Diseases, Faculty of Veterinary Medicine, Ghent University, Salisburylaan 133, 9820 Merelbeke, Belgium 2: Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands 3: Elanco Animal Health, Antwerpsesteenweg 51, 2350 Vosselaar, Belgium 4: Department of Pathobiology, University of Guelph, Ontario, Canada 5: Institute of Farm Animal Genetics, Friedrich-Loeffler-Institut, 31535 Neustadt-Mariensee, Germany
Publication date: August 1, 2012