Pathologic Diagnosis,Pathogen Identification And Whole Genome Sequencing Of Escherichia Coli In Red Panda

Red panda is a second class protected animal in China,which has unique ecological and ornamental value.Many zoos have introduced red panda for breeding.With the increase of the number of captive animals,reports of death caused by diseases are also increasing.Pathogenic escherichia coli is one of the most common pathogenic bacteria in clinical practice.Due to the complicated classification of pathogenic escherichia coli,the pathological manifestations of clinical animals infected with escherichia coli are different,mainly intestinal lesions.Clinical veterinarians cannot accurately determine the etiology only by the characteristics of the disease,so laboratory diagnosis is necessary for the diagnosis.In April 2018,our laboratory obtained a dead red panda tissue sample from XXX,and pathogeny diagnosis through histopathological and bacteriological methods were made.The comprehensive diagnosis was that the red panda died of multiple system failure due to sepsis caused by pathogenic escherichia coli infection.Routine isolation and identification,16Sr DNA sequence analysis and identification,drug resistance test,mouse challenge test,and bacterial whole genome sequencing were performed on the isolated strains.The results are as follows:1.On the ordinary AGAR medium,the colonies were round and grayish white,slightly convex,and red on the McConkey plate,with a single colony diameter of about1²mm.Under the microscope,most of the colonies were single distributed short rods of gram-negative bacteria without spores,about 1³ microns long.2.The 16SrDNA sequence of isolated strains was compared with the NCBI bacterial gene bank,and the coincidence degree with the existing escherichia coli sequences was more than 99%.3.The results of drug sensitivity test on 18 antibiotics showed that the bacteria was resistant to ampicillin and cefuroxime,moderately sensitive to cefazolin,and highly sensitive to other antibiotics.4.Mice challenge test obtained the lethal dose LD₅₀=6.5×10⁷ CFU/mL,and the pathological changes of mice challenge were mainly manifested as hemorrhagic enteritis and intestinal pathological changes of dead red panda.5.The whole gene sequencing results showed that the isolated strain was highly homologous with escherichia coli,and 21 drug-resistant genes and 713 virulence genes were detected.In summary,pathologic diagnosis and bacteriological identification confirmed that the red panda was fatal to pathogenic e.coli infection.The drug resistance test of isolated strains can provide reference for clinical drug selection of e.coli disease in red panda.The whole gene sequencing technology reveals the genetic characteristics of escherichia coli at the gene level,and further studies on the pathogenic mechanism of escherichia coli disease in red panda to the gene level,providing basic information for future research and development of relevant vaccines.