Resolving the taxonomy of emerging zoonotic pathogens in the Trichophyton benhamiae complex

Development and validation of a microsatellite marker-based method for tracing infections by Microsporum canis, Journal of Dermatological Science 70 (2) 123-129http://dx.doi.org/10.1016/j.jdermsci.2013.01.003You may download, copy and otherwise use the AAM for non-commercial purposes provided that your license is limited by the following restrictions:(1) You may use this AAM for non-commercial purposes only under the terms of the CC-BY-NC-ND license.(2) The integrity of the work and identification of the author, copyright owner, and publisher must be preserved in any copy.

The concept that clinical failure is linked to increased MICs is debatable, because significantly higher concentrations (in most cases at least 1,000 × the MIC) of the antifungals that were included in our study are routinely used in formulated products.

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Background -Dermoscopy is a non invasive technique allowing rapid and magnified in vivo observation of the skin and structures that lie beneath the skin surface. Various congenital and acquired hair shaft abnormalities may be also evaluated by dermoscopy and characteristic features of Microsporum canis-induced tinea capitis and trichotillomania in people have also been reported. Objectives -To describe the dermoscopic findings observed in cats with patchy alopecia due to Microsporum canis infection and in cats with self-inflicted hair loss. Animals -Twenty-four client-owned cats presented to a private veterinary referral practice. Methods -Dermoscopy was performed with both an handheld non-polarized light dermoscope at 10-fold magnification and a videodermoscope at 40-fold magnification. Results -At 10-fold magnification, the most characteristic findings observed in circumscribed lesions of cats with dermatophytosis were opaque, broken hairs slightly curved with an homogeneous thickness (comma-like structures) and a variable amount of brown-to-yellow greasy scales. In cats with self-induced alopecia, multiple hairs with a normal shaft suddenly and cleanly broken at different lengths, short tufts of hairs broken at equal level , hook-like and coiled hairs were observed. By videodermoscopy, hair shaft thickness was also measured. Conclusions -This observational descriptive study suggests that dermoscopy may represent an in vivo non-invasive technique helpful in differential diagnosis of patchy alopecia in cats.

Malassezia pachydermatis is a yeast inhabiting the skin and ear canals in healthy dogs. In the presence of various predisposing conditions it can cause otitis and dermatitis, which are treated with multiple antifungal agents, mainly azole derivatives. This manuscript aims to review the available evidence regarding the occurrence of resistance phenomena in this organism. Various findings support the capacity of M. pachydermatis for developing resistance. These include some reports of treatment failure in dogs, the reduced antifungal activity found against yeast isolates sampled from dogs with exposure to antifungal drugs and strains exposed to antifungal agents in vitro, and the description of resistance mechanisms. At the same time, the data reviewed may suggest that the development of resistance is a rare eventuality in canine practice. For example, only three publications describe confirmed cases of treatment failure due to antifungal resistance, and most claims of resistance made by past studies are based on interpretive breakpoints that lack sound support from the clinical perspective. However, it is possible that resistant cases are underreported in literature, perhaps due to the difficulty of obtaining a laboratory confirmation given that a standard procedure for susceptibility testing of M. pachydermatis is still unavailable. These considerations highlight the need for maintaining surveillance for the possible emergence of clinically relevant resistance, hopefully through a shared strategy put in place by the scientific community.

Whatever the mould species, reported treatment options include surgery and a series of antifungal drugs. The outcome is frequently poor, especially for Aspergillus infections, although various measures can be taken to maximise the chances of success, as discussed in this report.

Malassezia pachydermatis is a yeast that is frequently involved as a secondary/perpetuating factor in canine otitis externa. Topical therapies with different antifungal agents, mainly azole compounds, are generally successful in controlling the yeast overgrowth, but treatment failure and rapid recurrences are common. This study compared the in vitro antifungal susceptibility of M. pachydermatis isolates obtained from chronic and acute cases of otitis externa. The aim was to assess the possible onset of resistance mechanisms in isolates involved in long-lasting episodes with poor response to treatment. We evaluated the in vitro susceptibility to miconazole (MCZ) and clotrimazole (CTZ) of 42 isolates of M. pachydermatis obtained from dogs with chronic (group A, n = 25) and acute otitis (group B, n = 17), using a modified CLSI M27-A3 microdilution method. All isolates were inhibited by the antifungal agents employed, but Malassezia isolates from group A were significantly associated with higher minimum inhibitory concentration (MIC) values for both agents (Median MIC values: MCZ group A 2 µg/ml, group B 1 µg/ml; CTZ group A 8 µg/ml, group B 4 µg/ml). These findings prove that these isolates had a reduced in vitro susceptibility to the antifungal agents tested. However, it is unlikely that this could have any influence on the outcome of a topical treatment. Indeed, marketed products include concentrations of the tested agents that largely exceed even the highest MICs found in this study (in most cases at least 1,000 × the MIC, or greater). In conclusion, this study suggests that isolates of M. pachydermatis involved in chronic cases of canine external otitis and exposed to repeated antifungal treatments are unlikely to develop mechanisms of resistance of clinical relevance.