Isolation, Identification And Biologic Properties Research Of Shigella Boydii From Yak

Shigellosis, evoluted from Escheria coli, which was firstly found in1940s, is asingle intestinal pathogens that threaten human life all over the world. So far,researches including immune response, vaccine and the disease pathogenesis causedby shigella. Low pathogenic human dose, fecal-oral routie and childen major-infected,destruction of normal human instentinal tissue with sepsis, hyponatremia,hypokalemia, and low blood sugar abnormal were included as the virulencecharacteristics of Shigella on human.Human strains were the study heating-point. Strain variation and resistanceincreases, and a growing number of Shigella strains had been isolated from a varietyof animals, which is seriously harmful to human health. This study focused on theShigella strain isolated from yak which lives in a special environment, including aseries of morphological, biochemical characteristics, serological tests,16S rRNA genesequence analysis, drug resistance, LD50of BALB/c mice and histopathology,dynamic, as well as whole genome sequencing and genome comparison work.The results showed that morphological, culture and chemical characteristics ofthe isolation is consistent with that of Shigella. The isolate was serotyped as shigellaboydii type6. Phylogeny analysis based on16S rRNA indicated that the isolate hasclose relationship with shigella boydii and shigella sonnei in human, and has further relationship with the Shigella from other animals. The bacterium is not resistant toantibiotics commonly used. We isolated shigella boydii type6from yak for the firsttime. The isolate is highly pathogenic and phylogentically related to human Shigella,indicating important significance of yak Shigella in public health.The isolate is pathogenic to BALB/c mice, and the LD50is2.5×107.5CFU,slightly higher than the human strains. In addition to mouse intestine, liver necrosisand other pathological damages were showed in the animal test, then the relatedpathogenic and pathogenic process studies. The objective of this study was to researchthe pathology and pathological process of Shigella boydii from yak in BALB/c mice.Eighteen mice was divided into6groups, with3mouse per group. Nine organs ineach mouse were collected for HE and immunohistochemistry staining afterexperimentally infected with Shigella boydii from yak at6,18,30,42,54and66hs timepoints. The pathological changes and bacterial antigen location were observed. Totaltwelve blood biochemical index of the mice were detected. The HE staining resultsshowed that not only the pathological damage in intestine epithelial cell as reports inother references, but also coagulation necrosis under the epicardium, cellularinfiltration and granuloma in hepatic cells, inflammatory cells infiltrating in alveolarwall, pancreas epithelial cell swelling and cytoplasm dissolving and karyopyknosis orfragmentation. Immunochemistry staining results showed that positive bacterialantigen signals were found in cytoplasm of cardiac muscle cell, hepatocyte, alveolarwall, renal tubular epithelium cell, islet cell and intestinal epithelial cell. Pathologicaldamages, heart and hepatic necrosis of Shigella boydii from yak experimentallyinfecting mice was firstly reported in this study. Eleven kinds of blood biochemicalindex of experimental mice changed significantly in each infected time point exceptTG. This study verified that the severity of the pathology was positively correlatedwith the Shigella boydii antigen distribution, and the Shigella boydii from yak led to afast pathogenic damage to mouse tissues after inoculation for60h.Whole genome length of Shigella boydii isolated from yak is4,269,180base pair.Protein homology comparison showed that Escherichia coli O157: H7str EDL933ishighest proportion reached as15.28%(553/3619), and Shigella sonnei Ss046andShigella boydii Sb227are proportion reached as5.15%(174/3619) and2.38%(86/3619) respectively. Rfb, malA, glpK, envZ and other virulence genes present onthe chromosome confirm the isolation is a variety of virulence genes carried strain.And, gene missing such as kcpA, gulU lead to a function limitation when it invade tocells. Chromosomal genome GC content of isolate is between Shigella sonnei,Shigella boydii, Shigella dysentery reference strains and Shigella flexneri as well as E.Coli reference strains, which maintain a certain protein secondary structure and is infavor of accurate translation.It was first time that isolating shigella from yak. Morphological, biochemicalcharacteristics, serological tests,16S rRNA gene sequence analysis, drug resistance,pathology to BALB/c mice, as well as whole genome sequencing and genomecomparison work were done in this study. This study enriches the epidemiologicaldata of shegellosis, and also made foundation for the further research.