In vitro evaluation of enzymatic virulence activities and antifungal susceptibility profile of Microsporum canis strains from various sources
Microsporum canis is one of the major pathogenic and most prevalent dermatophytes of domestic animals causing tinea capitis which differs from one country to another worldwide. To have an effective therapy and to direct future research, it is essential to understand the virulence factors and antifungal susceptibility profiles of M. canis infection. The present study assesses the capability of M. canis strains from different hosts in producing virulence factors, evaluates the in vitro antifungal profile and assess the relationship between virulence, antifungal profile and occurrence of lesions from different hosts. A total of 100 M.canis strains grouped into origin and presence of lesions humans (n = 10) or animals with skin lesions (n = 64) and without skin lesions (n = 26) was used to evaluate the production of virulence enzymes and thermotolerance activity. Additionally, the in vitro activity of 7 antifungal drugs was evaluated according to CLSI document M38-A2 methodology.
M. canis strains showed phospholipase Pz (94.1%), hemolytic Hz (92. 2%) lipase Lz (100%) and catalase Ca activities (100%). The Lz and Ca values were lower in strains without lesions (p < 0.05). The growth of colonies at 28°C was better than at 35°C (p < 0.05). The number of low thermotolerance (76.5%) strains were higher than those with high thermotolerance (23.5%) (p < 0.05). VOR, TER and PSZ were the most active drug against M. canis strains, followed by KTZ GRI, ITZ and FLZ in rank activity order for the different hosts. Significant positive correlation of low and high VOR/FLZ MICs with Hz and Ca production was observed suggesting that these enzymes can play a significant role in the increased azole probable resistance. Our results confirmed that reliable determination of the relationship between virulence factors and antifungal probable resistance may highlight new therapeutic strategies based on the involvement of the virulence mechanism in the effectiveness of treatment.