Experimental Study Of Backusella Circina Var.circina’s Pathogenicity To Human Nails And Hair Perforation In Vitro

Objective: Backusella circina belong to the Zygomycetes subphylum,Mucorales,widely distributed in the nature.A model of fungal peretration to human nails was established to study if B.circina var.circina could infect human nails,and to compare the differences between B.circina var.circina and Trichophyton mentagrophytes by measuring The penetration time.Then The microscopic changes of the damaged nail structure would be observed by the scanning electron microscope(SEM),and the damage degree of the two strains to the nails was compared.On the other hand,Hair perforation tests were carried out in four different age groups to evaluate the invasive ability of B.circina var.circina.The time difference among different age groups was analyzed and the susceptible population of hair damage was speculated.At the same time,the microstructure of hair was observed by light microscope and SEM.Methods: 1.The model of fungal penetration was established and divided into two groups:the B.circina var.circina group and the Trichophyton mentagrophytes group.Trichophyton mentagrophytes was regarded as the positive control bacterium.The penetration time of each group was observed and recorded,and the difference between the two groups was compared.At the same time,the positive nails and the negative control nails in each group were placed under the SEM to observe the microstructure changes of the dorsal and ventral sides.2.Collected healthy hairs of four diferent age groups(less than 2years old,2～13 years old,14～19 years old and older than 19 years old),and placed them in SDA solid medium.Then inoculated on the hair with the fungal suspension of B.circina var.circina and Trichophyton mentagrophytes respectively,and cultured in 27℃ incubator.After inoculation,we observed the changes of hair structure under light microscope every day.The damaged hairs were further photographed by SEM to observe the microstructure of infected hairs.Results: 1.In this experiment,the two fungal strains could penetrate through the nail.The penetration time of B.circina var.circina was 2(2,3)d,and that of Trichophyton mentagrophyte was 5(4.25,6.00)d.The penetration time of B.circina var.circina was shorter than that of Trichophyton mentagrophyte(P<0.05).Scanning electron microscopy showed that hyphaes of B.circina var.circina could penetrate the horn cells of nails,and the morphology of keratinocytes changed,and the intercellular space varied.2.In hair perforation test,the structure of hair infected by fungi changed.In all age groups,the perforation time of B.circina var.circina to hair were longer than that of Trichophyton mentagrophyte(P<0.05).The hair perforation time of the two strains was different in different age groups(P<0.05).The results showed that there were significant differences between the younger than 2 year-old and2～13 year-old,14～19 year-old groups(P<0.05).And there were also differences between the older than 19 year-old and 2～13 year-old,14～19year-old groups(P<0.05).Scanning electron microscopy showed that Trichophyton mentagrophytes had more serious damage to hair than B.circina var.circina.Conclusion:1.B.circina var.circina can penetrate nail plate,however,the penetration time was shorter than that of Trichophyton mentagrophytes;2.B.circina var.circina could infect human hair,the damage of B.circina var.circina to hair was milder than that of Trichophyton mentagrophytes;3.B.circina var.circina was more likely to infect the hair of children under 2 years old and adults over 19 years old.