Identification And Pathogenicity Of Lichtheimia Ramose From Goat

Lichtheimia ramose is a conditionally pathogenic fungus that is widely present in the environment and easily invades when the host is immunocompromised,thus causing widespread infection to the organism.In order to investigate the pathogenic mechanism of Lichtheimia ramose in depth,this experiment was conducted using fungal culture,scanning electron microscopy,PCR amplification,virulence factor assay,drug sensitivity test,mouse infection test,PAS and GMS staining,hematoxylin-eosin(HE)staining and transmission electron microscopy.The results showed that strain LYSF001 was isolated from the epidermis of sheep and the mycelium was observed to be white with a downy texture in culture;the sporangia were observed to be spherical or subspherical on microscopic examination;the periphery of the sporangia was observed to be radially raised on scanning electron microscopy,and the morphology was initially observed to be consistent with the morphological characteristics of Lichtheimia ramose.The ITS gene was amplified by PCR to obtain an 865 bp fragment,which shared 98.9 % homology with Lichtheimia ramose(MT853218.1)in Gen Bank.The strain LYSF001 was comprehensively identified as Lichtheimia ramose.Five virulence genes,Cal A,PKP2,Lae A,Alp2 and Asp F1,were detected by PCR.Drug sensitivity tests showed that strain LYSF001 was sensitive to amphotericin B and itraconazole,drug resistance to voriconazole and caspofungin.Infection test in mice showed,the morbidity rate of mice in the rubbing group skin was 70% and mortality rate was 0;the morbidity rate of mice in the intraperitoneal injection group was90% and mortality rate was 40%.The skin of the mice in the rubbing group skin showed positive GMS staining,thickening of the cuticle and destruction of the reticular layer by HE staining.The organ index of the spleen in the intraperitoneal injection group was significantly higher than that in the control group(P<0.05).ITS genes were amplified in heart,liver and spleen tissues,and hyphae were visible in PAS and GMS staining of liver and kidney tissues.HE staining showed lesions such as enlarged cardiomyocytes,swollen and degenerated hepatocytes,congested splenic red medullary area and swollen and degenerated renal tubular epithelial cells.Transmission electron microscopy showed that hepatocytes in the intraperitoneal injection group had increased mitochondrial density.This indicates that the strain LYSF001 isolated from goat is pathogenic and provides a scientific basis for the further elaboration of the pathogenic mechanism of Lichtheimia ramose and the clinical control of mucormycosis.