To identify the contaminated bacteria on the surface of goose eggs and analyze their biological characteristics and pathogenicity,the isolates were identified using Enterobacteriaceae identification medium,Gram staining,PCR method,and MLST typing,and the drug susceptibility was measured by agar diffusion method,and analyzing the tolerance of isolated strain to various environments using bacterial counting method(UV,75%ethanol,different concentrations of NaCl).The isolated strain virulence genes were detected by PCR method;Subcutaneously inject the isolated strain at doses of 109cfu,108cfu,and 107cfu to infect 3-day-old goslings and ducks.The observation lasted for 8 days,and the symptoms and mortality were recorded.3-day-old goslings and ducklings were orally infected with 109cfu and 108cfu doses to analyze weight changes and bacterial load in organs.The results revealed that the isolated strain showed a black metallic luster colony in XLD medium,and a red medium-sized rod shape after Gram staining.The typical Salmonella target band was amplified by PCR,and the MLST typing was ST2039.The isolate was identified as Salmonella Potsdam,named JX202305.The drug susceptibility results showed that the isolate was sensitive to most antibiotics such as doxycycline,compound sulfamethoxazole,while insensitive to ceftriaxone,cefotaxime and nalidixic acid.The environmental stress tolerance test results showed that the number of the isolate decreased from 9×108cfu/mL to 3000cfu/mL,100cfu/mL,40cfu/mL and 0 after UV irradiation for 5min,10min,15min and 20min,respectively.The difference is extremely significant compared to the control group(P<0.001),indicating that the isolated strains have low UV tolerance.Treatment with 75%ethanol for 1min led to a decrease in bacterial survival rate to 0,which indicated that 75%ethanol has a strong killing effect on the isolated strain.Compared to the control group,separate treatment with 5%,10%,15%,and 20%NaCl concentrations for 30min and 60min had no significant impact on bacterial survival(P>0.05);while treatment with 25%NaCl for 30min and 60min resulted in a decrease in survival rate to 38%and 10%,respectively(P<0.05).The results indicated that the isolated strains have strong tolerance to NaCl.The results of the subcutaneous injection infection test showed that at does of 109cfu,108cfu,and 107cfu,the mortality rates of goslings were 90%,60%,and 20%,respectively,while the mortality rates of ducklings were 50%,10%,and 0,respectively,indicating that the isolated strain has stronger pathogenicity to goslings than to ducks;The results of oral infection test showed that there was no significant change on the body weight of goslings and ducklings in the infection group compared with the control group(P>0.05),and the invasion ability of the isolate to the liver and spleen of goslings was stronger than that of ducklings.The detection of virulence gene showed that except for the cdtB virulence gene,the remaining 15 virulence genes,such as sitC,stn,invA were all positive.This study revealed the biological characteristics of Salmonella Potsdam isolated strain JX202305 and evaluated the pathogenicity difference goose eggs-derived strains to goslings and ducklings for the first time,which provided scientific data for the scientific prevention and control of this serotype and enriched the serotype data of Salmonella spp.
goose eggsSalmonella Potsdamisolation and identificationpathogenicity
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NSTL
万方数据
