Study On Pathogenicity And Molecular Features Of Main Pathogen Causing Lamb Diarrhea Syndrom

A total of 167 stool samples of 10-day-old lambs with diarrhea were collected from 21 farms in Gansu and Qinghai province.Rotavirus,Cryptosporidium and Giardia performed using immuno-colloid gold technique quad kit of Rotavirus-cryptosporidium-giardia-E.coli k99.Pathogenic bacteria was detected by 16 S rDNA amplification.103 dubious pathogenic E.coli strains were carried out pathogenicity tested using 110 Kunming mice,then etiology and pathology diagnosis in mice were proceeded.The results indicated that the major pathogen was pathogenic E.coli that accounted for 61.68%,and these strains performed different pathogenicity.The 8 virulence genes of pathogenic E.coli were detected by PCR technique.The results showed that E.coli strains carried multiple virulence genes simultaneously,which caused lamb diarrhea in Gansu and Qinghai province.These strains carried ipaH,eae and stxl were common.Drug sensitivity of pathogenic E.coli were performed using Kirby-Bauer Paper flakes diffusion method to test the resistance of 15 antibiotics.The results indicated that the rate of drug resistant of E.coli to Penicillin and Lincomycin was over 95%,howener Ertapenem,Meropenem,PolymyxinB and Polymyxin Sulfate possessed lower resistant rate less than 10%.The resistance genes of aminoglycoside,tetracycline and ?-lactam antibiotics of pathogenic Escherichia coli were detected by PCR mothed,then the relevance between the drug resistance genes and resistant phenotype was analyzed.The detection rates of Tetracycline resistance genes tetA and tetB were 83.50% and 68.93% respectively,and there was a high positive correlation between tetA gene and resistant phenotype,and a moderate correlation between tetB gene and resistant phenotype.blaTEM and blaSHV resistance genes of Escherichia coli to Tetracycline detection rates were 63.11% and 56.31%,respectively,and the two resistance genes correlated significantly with the resistant phenotype of Ampicillin.Resistant genes aac(3)-I gene of Escherichia coli to aminoglycoside also had a higher detection rate of 78.64% and highly correlated positively with the resistant phenotype of kanamycin.This study presented that the major pathogen was pathogenic Escherichia coli,which caused lamb diarrhea disease in Gansu and Qinghai province,but the pathogenicity genes exist difference among the strains.The strains that carried virulence genes of ipaH,eae and stx1 were common in sheep farms in two provinces,and showed strong resistance to Penicillin and Lincomycin.And most strains carried resistance genes of tetA and tetB to tetracycline antibiotics,blaTEM and blaSHV to?-lactam antibiotics and aac(3)-I to aminoglycoside.Cconsequently,the strains existed a certain correlation between resistant genes and resistant phenotype among these strains.