Abstract
Emergence of multidrug-resistance in Staphylococcus pseudintermedius (SP) has increased interest in topical therapy as an alternative to systemic antibiotics in canine pyoderma. The antifungal imidazole, clotrimazole, is contained in numerous licensed canine ear preparations. Its in vitro activity against SP has not been evaluated, although previous studies have shown that the related imidazole, miconazole, has significant anti-staphylococcal efficacy. We therefore determined minimum inhibitory concentrations (MICs) of clotrimazole amongst 50 SP isolates (25 methicillin-resistant [MR]SP and susceptible [MS]SP) collected from dogs in Germany during 2010–2011 using an agar dilution method (CLSI VET01-A4). MICs amongst MRSP and MSSP were comparable (MIC50 and MIC90 = 1mg/L for both groups, p = 0.317); overall, 49 isolates had MIC = 1 mg/L and one had MIC = 0.5 mg/L. The relatively low MICs obtained in this study are likely to be exceeded by topical therapy and thus further clinical evaluation of clotrimazole use in canine superficial pyoderma and otitis externa caused by MRSP and MSSP is now warranted.
Highlights
The relatively low minimum inhibitory concentrations (MICs) obtained in this study are likely to be exceeded by topical therapy and further clinical evaluation of clotrimazole use in canine superficial pyoderma and otitis externa caused by methicillin-resistant S. pseudintermedius (MRSP) and methicillin-susceptible counterparts (MSSP) is warranted
Staphylococcus pseudintermedius is routinely isolated from canine otitis externa and superficial pyoderma, two of the most common dermatological diseases encountered by first opinion veterinary practitioners [1,2]
MIC values were similar to those reported for clotrimazole, miconazole and econazole against a single reference strain of human-derived S. aureus [12], and for 18 strains of MRSA obtained from human burn patients in China
Summary
Staphylococcus pseudintermedius is routinely isolated from canine otitis externa and superficial pyoderma, two of the most common dermatological diseases encountered by first opinion veterinary practitioners [1,2]. The emergence of methicillin-resistant S. pseudintermedius (MRSP), resistant to most or all systemically licensed antimicrobials available to veterinary practitioners [3], paralleled by recognition of the risk of zoonotic infections for pet owners [4,5], has led to increased interest in a topical therapeutic approach using narrow-spectrum antimicrobials [6]. Clotrimazole is a broad-spectrum anti-fungal imidazole that is widely used in human medicine for the topical therapy of dermatophytosis, vulvovaginal and oropharyngeal candidiasis [7]. It is a component of polypharmaceutical ear drops licensed for use in dogs in various European countries; this is primarily due to its activity against Malassezia pachydermatis [8], a commensal yeast and important ear and skin pathogen in this species [9]. Clotrimazole and related imidazoles have been shown to have a narrow spectrum of antibacterial activity, encompassing human-derived S. aureus, S. epidermidis, Mycobacterium smegmatis and Streptomyces spp., but not Escherichia coli and Streptococcus pyogenes [10,11,12,13].
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