In vitro miconazole susceptibility of meticillin-resistant Staphylococcus pseudintermedius and Staphylococcus aureus

The emergence and dissemination of meticillin-resistant staphylococci has created significant treatment challenges in veterinary medicine and increased interest in topical therapy for superficial infections. Concern has been expressed regarding the use of some topical antimicrobials in animals because of the potential for emergence of resistance, and additional options are required. Miconazole has limited antibacterial properties that include antistaphylococcal activity.

The objective of this study was to assess the in vitro susceptibility of Staphylococcus pseudintermedius and Staphylococcus aureus to miconazole.

In vitro susceptibility of 112 meticillin-resistant S. pseudintermedius (MRSP), 53 meticillin-resistant S. aureus (MRSA) and 37 meticillin-susceptible S. pseudintermedius (MSSP) to miconazole was assessed using agar dilution.

The minimal inhibitory concentration (MIC) range, MIC(50) and MIC(90) for MRSP were 1-8, 2 and 4 μg/mL, respectively. Corresponding results for MRSA were 1-8, 2 and 6 μg/mL, and for MSSP 1-4, 2 and 2 μg/mL. The MIC for MSSP was a significantly lower MIC than that for both MRSP (P = 0.006) and MRSA (P < 0.001), while the MIC for MRSP was significantly lower than that for MRSA (P = 0.001).

These in vitro data suggest that miconazole could be a useful therapeutic option for superficial infections caused by meticillin-susceptible and meticillin-resistant staphylococci, but proper clinical investigation is required.