黄牛源A型产气荚膜梭菌生物学特性及全基因组测序分析OA

To determine the causative agent of sudden death cases in cattle at a large-scale farm in Hezhou city,Guangxi,tissue samples from the intestine,lung,and spleen were aseptically collected during necropsy.A comprehen-sive analysis was performed,including bacterial isolation and identification,biochemical testing,growth curve draw-ing,antibiotic susceptibility testing,pathogenicity assessment,and whole-genome sequencing.The result showed that through isolation and purification,the bacterium was identified as Clostridium perfringens type A based on its bio-chemical profile and the presence of type-specific virulence genes.The isolate was designated strain HZ25-1.Antibio-tic susceptibility testing demonstrated that the strain was resistant to nine commonly used antimicrobials,including ceft-iofur,cefalexin,cefoxitin,ect.,while remaining susceptible to four antibiotics,such as penicillin,amoxicillin,ampicil-lin and ofloxacin.Pathogenicity experiments confirmed that all challenged mice died within 24 hours,and the identical bacterium was recovered from the lesions,which confirmed its pathogenicity.The whole genome sequencing analysis revealed that the HZ25-1 strain has a genome length of 3 335 730 bp,with a GC content of 28.12％.The genome was found to be structured with 3 003 coding sequences(CDSs),67 tRNAs,66 ncRNAs,129 repetitive sequences,and 4 ge-nomic islands.Based on integrated annotations from the GO,KEGG,and CAZy databases,it was demonstrated that growth of Clostridium perfringens is primarily supported by the enzymatic hydrolysis of starch and sucrose.Annotation against the VFDB database indicated that the pathogenicity of HZ25-1 was likely enhanced by the synergistic action of the plc,cpb2,and pfoA virulence genes.Furthermore,when annotated using the CARD database,the ermQ and rpoB genes were identified as key determinants conferring the multidrug-resistant phenotype observed in the HZ25-1 strain.Phylogenetic analysis of the 16S rRNA gene showed HZ25-1 was most closely related to a Greek buffalo strain(JX311438.1),and clusters with strains from Indian cattle(KF999873.1),Shandong deer(OK175676.1),Yunnan goats(MK156683.1),and Qinghai yaks(MW980103.1),suggesting potential cross-regional and cross-host transmission.