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In vitro antifungal susceptibility of Malassezia pachydermatis strains isolated from dogs with chronic and acute otitis externa.
Mycopathologia. 2014 Oct; 178(3-4):315-9.M

Abstract

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.

Authors+Show Affiliations

Settore di Parassitologia e Malattie Parassitarie, Dipartimento di Scienze Veterinarie, Università degli Studi di Torino, Via Leonardo da Vinci 44, Grugliasco, 10095, Turin, Italy, elisa.chiavassa@unito.it.No affiliation info availableNo affiliation info available

Pub Type(s)

Comparative Study
Journal Article
Research Support, Non-U.S. Gov't

Language

eng

PubMed ID

25031085

Citation

Chiavassa, E, et al. "In Vitro Antifungal Susceptibility of Malassezia Pachydermatis Strains Isolated From Dogs With Chronic and Acute Otitis Externa." Mycopathologia, vol. 178, no. 3-4, 2014, pp. 315-9.
Chiavassa E, Tizzani P, Peano A. In vitro antifungal susceptibility of Malassezia pachydermatis strains isolated from dogs with chronic and acute otitis externa. Mycopathologia. 2014;178(3-4):315-9.
Chiavassa, E., Tizzani, P., & Peano, A. (2014). In vitro antifungal susceptibility of Malassezia pachydermatis strains isolated from dogs with chronic and acute otitis externa. Mycopathologia, 178(3-4), 315-9. https://doi.org/10.1007/s11046-014-9782-0
Chiavassa E, Tizzani P, Peano A. In Vitro Antifungal Susceptibility of Malassezia Pachydermatis Strains Isolated From Dogs With Chronic and Acute Otitis Externa. Mycopathologia. 2014;178(3-4):315-9. PubMed PMID: 25031085.
* Article titles in AMA citation format should be in sentence-case
TY - JOUR T1 - In vitro antifungal susceptibility of Malassezia pachydermatis strains isolated from dogs with chronic and acute otitis externa. AU - Chiavassa,E, AU - Tizzani,P, AU - Peano,A, Y1 - 2014/07/17/ PY - 2013/07/31/received PY - 2014/06/26/accepted PY - 2014/7/18/entrez PY - 2014/7/18/pubmed PY - 2015/5/20/medline SP - 315 EP - 9 JF - Mycopathologia JO - Mycopathologia VL - 178 IS - 3-4 N2 - 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. SN - 1573-0832 UR - https://www.unboundmedicine.com/medline/citation/25031085/In_vitro_antifungal_susceptibility_of_Malassezia_pachydermatis_strains_isolated_from_dogs_with_chronic_and_acute_otitis_externa_ L2 - https://dx.doi.org/10.1007/s11046-014-9782-0 DB - PRIME DP - Unbound Medicine ER -