Studies On Serotypes, Adhesion And Drug Resistance Of Pathogenic E.coli From Piglets In Xining

Strains of piglet pathogenic E.coli were isolated from Large-scale pig farms in Xining. Serotype and epidemic predominant serotypes were isolated and identified. Adhesion of pilus from the main epidemic bacterial strains was examined and antigen immunoassay was carried out. 14 kinds of antibiotic were adopted on drug resistance detection of epidemic strains by the means of NCCLS.253 strains of pathogenic E.coli were isolated and identified from 247 samples from diarrhea piglets by cotton of rectal examination and 39 tissues samples from piglets of doubtful death of edema disease from 8 pig farms in Xining. The total rate of checking out was 88.5% (253/286). 233 strains of pathogenic E.coli were checked out from diarrhea piglets and the rate of checking out was 94.3% (233/247). 20 strains of pathogenic E.coli were checked out from edema disease piglets and the rate of checking out was 51.3%. These results showed that the diarrhea of piglets was resulted from infection of pathogenic E.coli, but there were differences in detectable rate among pig farms. Serotype of O8, O54, O139, O141, O138, O147, O9, O111, O145, O20, O101 and O45 existed in this area. The 191 strains bacteria, accounting for 78.3% of 244 detected stains, were O8, O139, O141, O138, O111 serotype, so these serotypes were the predominant serotypes in this area.Pilus types of 10 strains of O138 and O141 were examined respectively, using methods of MRHA and MSHA. The results showed that 20 strains of them express F1 pilus, which can coagulate erythrocyte of rabbit, Guinea pig, sheep and human; and 8 strains of them express F4 pilus (k88), which can coagulate erythrocyte of chicken and Guinea pig. The fimbria was extracted from the bacterial by the means of heating, and the vaccine of fimbrial antigen adjuvant of water-in-oil emulsion preparation was prepared, which included water phase, 98% fimbrial antigen and 2% Tween 80, and oil phase, 94% white oil and 6% span 80, with the rate of 1:1. The vaccine was inoculated in rabbit, and the antibody titer was 1:64. The rate of coagulation of fimbrial antigen to Guinea pig erythrocyte was 1:640 in the bovine-heart agar medium, bacteria in which expressed more F4 pilus than others medium.Drug resistance detection of 170 strains pathogenic E.coli were examined using 14 kinds antibiotics according to the standard method from NCCLS. The result showed that all strains have resistance to the antibiotic, and the rates of resistance to Penicillin, Ampicillin, Streptomycin and Tetracycline were 87.1%, 80.6%, 62.9% and 56.5% respectively. No. 8, 20, 39, 38, 25, 17, 8, 6, 5, 2 and 2 strain of bacteria have ability of resistance to 2 to 12 kinds of antibiotics. There are 102 strains accounting for 60.0% of total bacteria have multi-ply abilities of resistance, namely having ability of resistance to 4, 5 and 6 kinds of antibiotics; and these tests showed that the predominant strains in Xining are more sensitive to Polymyxin B, Norfloxacin, Ciprofloxacin , Ofloxacin and etc.