Comparison of virulence of differentSporothrix schenckiiclinical isolates using experimental murine model

Abstract

The virulence of two strains of Sporothrix schenckii isolated from patients with lymphocutaneous or disseminated sporotrichosis were examined in BALB/c mice (Group 1 and 2, respectively). The mice were inoculated subcutaneously into the left hind footpad with 4 x 10(6) S. schenckii yeast cells in order to evaluate (i) the development of cutaneous lesions, (ii) signs of inactivity, (iii) weight loss, (iv) survival rates, (v) number of viable yeast cells in the lungs and spleen, (vi) splenic index, (vii) extent of organ lesions, and (viii) immunological responses. Comparison of the two groups showed more severe disease in Group 2 mice that developed significant weight and hair loss associated with inactivity and left hind footpad lesions that extended close to the testicular area. The histopathology and large number of viable microorganisms isolated from the spleen confirmed the higher invasive ability of this strain. Moreover, a decrease of an in vitro specific lymphoproliferative response and IFN-gamma production were observed over time in Group 2 mice. As a result, at the end of the experiment, the S. schenckii-antigen (Ss-Ag) response was considered negative with a stimulation index (SI) = 2. In contrast, Group 1 mice presented a positive response to Ss-Ag (SI = 14.1). These results confirm the existence of different virulence profiles in S. schenckii strains. In addition, the use of subcutaneous inoculation as a suitable route for verification of the pathogenicity of this fungus in the murine model was confirmed.

Characterization of virulence profile, protein secretion and immunogenicity of differentSporothrix schenckii sensu strictoisolates compared withS. globosaandS. brasiliensisspecies

“…isolates, they were less virulent than S. brasiliensis (Ss54, CBS 132990) isolate. In general, the virulence profiles of isolates obtained by CFU and survival assay S. luriei creating a well-supported clinical clade what is in agreement with De Beer et al 36 Various studies using animal models have shown differences in virulence among Sporothrix isolates, correlating the pigmentation of conidia, thermotolerance, 31 routes of infection 32 and origin 33,34 to the degree of virulence, nevertheless, none of these studies take into consideration the new taxonomy used for the clinical S. schenckii complex species. 11,12 In this study we did not find correlation between virulence profile of our isolates with thermotolerance or geographic origin (data obtained in our previously study 9 ) of them.…”

“…35 Some comparative studies were conducted correlating the route of experimental infection 32 or clinical manifestation in humans with the virulence degree of different isolates. 33,34 Recently, Arrillaga-Moncrieff et al 2,3 showed different degrees of virulence among S. schenckii s. str., S. brasiliensis and S. globosa species.…”

“…30 On the other hand, other studies showed the differences in Sporothrix virulence and the clinical presentation of the disease, geographic origin, genotype and thermotolerance. [31][32][33][34] The time of cultivation of yeast and mycelial cells of S. schenckii induces changes in cell wall composition, causing a decrease of pathogenic power. 35 Some comparative studies were conducted correlating the route of experimental infection 32 or clinical manifestation in humans with the virulence degree of different isolates.…”

Sporothrix schenckii and Sporotrichosis

“…The virulence of S. schenckii is one of the factors thought to play a role in the development of sporotrichosis (32), but there are discordant results concerning disease evolution in experimental sporotrichosis with S. schenckii clinical isolates from cutaneous and disseminated infection (29,176), indicating that host immune responses also substantially participate in the progress of sporotrichosis (32).…”

“…Other studies have reported similar results. Brito et al (29) studied the virulence of two strains of Sporothrix schenckii, isolated from patients with lymphocutaneous (group 1) or disseminated (group 2) sporotrichosis, by inoculating BALB/c mice. Comparison of the two groups revealed more severe disease in group 2 mice.…”