Melanin Production Of Different Clinical Forms Of Sporothrix Schenckii

Sporotrichosis is a subacute or chronic deep mycosis caused by the dimorphic pathogenic fungus,Sporothrix schenckii.The most common presentation is cutaneous disease, which is classified into cutaneous sporotrichosis.Pulmonary,osteoarticular, eye,central nervous system,heart, liver, spleen, pancreas, kidney, testes and thyroid and other organs infections are less common and usually occur in immunosuppressed individuals,which is classified into systemic sporotrichosis. The different clinical forms of sporotrichosis depend on the relationship between the host’s immune status and intrinsic factors of the pathogen.Since melanin is found as a fungal virulence factor,it has occupied an increasingly important position in the study of fungal virulence.Melanization has been associated with protection of fungal against harsh environmental conditions,such as ionizing radiation, oxygen, ultraviolet radiation and extreme temperatures. Melanization can resist the attack by host-macrophages and can also decrease fungal susceptibility to antifungal drugs.Researches for Sporothrix schenckii suggest that melanin can prevent S. schenckii from being killed, enhance the ability to resist ultraviolet radiation,and affect the defense mechanisms of the host by reducing phagocytosis and scavenging reactive oxygen and nitrogen species during infection.Animal experiments suggest that the existence of melanin perhaps make it easier for Sporothrix schenckii to invade and disseminate in the host tissue.Melanin plays an important role in the pathogenesis of fungi.Research of the relationship between fungal melanin and the virulence is an important tool to study the pathogenesis of fungi and fungal drug resistance.Measurement of different fungal melanin production and evidence of the relationship between melanin production and the virulence of the fungus can be useful to the study on fungal pathogenesis Objective:Through the measurement of melanin production of S.schenckii conidia from different clinical forms that cultivated in the same time and the analysis of the result,we try to evaluate the correlation of fungal melanin production and different clinical forms,and then analyze the melanin’s impact on fungal virulence.Methods:Forty one strains of Sporothrix schenckii isolated from different patients (20from fixed cutaneous,20from lymphocutaneous and1from disseminated cutaneous) were plated on Sabouraud Dextrose Agar at25℃for one and two weeks.The conidia obtained from the strains were collected and then measured through the detection kit.The results were analyzed by using statistical software.Results:The strains grows rapidly on Sabouraud dextrose agar at room temperature, producing cream-colored, smooth or wrinkled, moist colonies.Then some strains turned brown to black after a few days of cultivation and formed typical brown mycelial colonies.Though some strains produce pigment slowly and even do not turn black after2weeks incubation.Most remained cream-colored colonies and only a few of dark pigment surrounded the colonies.The degree of melanization on different colonies was scored,and there was no significant difference between the fixed cutaneous group and lymphocutaneous group(P>0.05). Forty one strains of Sporothrix schenckii isolated from different patients cultivated for1and2weeks at room temperature.After cultivated,melanin content of conidia were measured.The results were analyzed using statistical software,and there was no significant difference of melanin content between the fixed cutaneous group and lymphocutaneous group during the same time(P>0.05).There was a significant difference between different cultivating time,and the measured value cultivated for2weeks is higher than the ones cultivated for1week(P<0.05).There was no significant difference of the correlation between Measurement results and the degree of melanization on different colonies(P>0.05).Conclusion:In this experiment41Sporothrix schenckii clinical isolate strains were confirmed to produce melanin and the average melanin production of conidia cultivated for1week and2weeks at room temperature were7.10±1.31μg/107cell and7.81±1.38μ g/107cell.The degree of melanization on different colonies was scored,and there was no significant difference between the fixed cutaneous group and lymphocutaneous group.There was no significant difference of melanin content between the fixed cutaneous group and lymphocutaneous group during the same time.There was a significant difference between different cultivating time,and the measured value cultivated for2weeks is higher than the ones cultivated for1week.There was no significant difference of the correlation between Measurement results and the degree of melanization on different colonies.The colonies’ color turned lighter after repeated passaging.