Investigation On Some Bacterial Pathogens Of Bovine Diarrhea In Hohhot And Establishment Of Triple PCR Detection Method

Bovine bacterial diarrhea is a kind of digestive tract disease with diarrhea and dehydration as the main symptoms.The main pathogens are pathogenic Escherichia coli and Salmonella.In order to study the epidemic characteristics of bovine bacterial diarrhea pathogens in Hohhot,219 fresh fecal samples from 8 large-scale cattle farms around Hohhot were collected for epidemiological investigation of bovine bacterial diarrhea pathogens.Escherichia coli and Salmonella were isolated for morphological and biochemical identification.170 positive fecal samples of Escherichia coli were determined,and the positive rate was 77.6%;There were 30 Salmonella positive fecal samples,and the positive rate was 13.7%;75 strains of Escherichia coli isolated from diarrhea feces were selected for serological identification.27 strains were identified as pathogenic Escherichia coli,with a positive rate of 36.0%.Among them,22 strains of ETEC were 2 of O168,1 of O27,1 of O6-O28,3 of O20,1 of O6,2 of O15,4 of O153,1 of O126,2 of O128,2 of O8,1 of O159 and 2 of O25;4 strains of EPEC,1 of O26-O55,1 of O114,1 of O127,1 of O125 and 1 EAEC O44;Five strains of pathogenic Escherichia coli were selected for mouse challenge test,and all mice were pathogenic.The drug sensitivity test of 75 strains of Escherichia coli showed that the drug resistance rate to sulfa compound sulfamethoxazole was as high as 78.7%;The resistance rate to imipenem was the lowest,9.3%;The rate of multidrug resistance was 96%;Most of them were resistant to 13 kinds of antibiotics,accounting for 1.3%;It is mainly resistant to 5-7 kinds of antibiotics,accounting for 56%.In order to quickly detect the main pathogenic Escherichia coli ETEC and Salmonella causing bovine diarrhea,a triple PCR detection method was established according to the virulence genes st and lt of ETEC and the virulence gene inv A of Salmonella,which can specifically detect two bacterial pathogens.The sensitivity of St,LT and inv A were 3ng / UL,4.5ng/ul and 3ng / UL respectively.85 clinical samples were detected by the method established in this test,15 of which were ETEC positive,and the positive rate was 17.6%;There were 10 positive samples of Salmonella,and the positive rate was 11.8%.This experiment provides scientific basis and technical support for the prevention and control of bovine diarrhea in Hohhot.