Surveillance Of Drug Resistence And ERIC-genotyping Of Avian Pathogenic Escherichia Coli

The major objective was to study the biological characteristics and the changing tendency in drug resistance of avian pathogenic Escherichia coli(E.coli)in some regions of China,discuss the epideminology and mechanism of drug resistance at molecular level, and provide information for the prevention and treatment of avian Escherichia colibacillosis as well as the development of new veterinary pharmaceuticals.3 parts were included in this study:1.The isolation,identification and analysis of serotype O of avian pathogenic Escherichia coli33 bacterial strains were isolated from dead or sick chicken with typical symptoms of avian Escherichia colibacillosis at chicken farms in Northeast China,Hebei,Shandong and East China regions.21 strains were determined by biochemical tests to be avian E.coli and are highly pathogenic tested by inoculating chicken and Mus musculus albus.Slide and tube agglutination tests were used combinatively to serotype the 21 strains,among which 8 strains are determined to be of 3 serotypes:O₈₈(4),O₂₆(3)and O₇₈(1)respectively, accounting for 38.1%of these 21 strains.The other 13 strains were not able to serotyped (Self-agglutination in 2 strains).O₈₈strains are distributed in Northeast China,Shandong and Eastern China,and O₂₆strains in Hebei,Shandong and Eastern China,therefore being predominant serotypes.With the many serotypes,complex distribution and regional disparity of avian pathogenic E.coli,the determination of Serotype O provides better evidence for the prevention of avian pathogenic E.coli.2,Antibiotic susceptbility tests on 21 avian pathogenic Escherichia coli isolatesKirby-Bauer testing recommended by the World Health Organization(WHO)were applied to 21 strains with 12 antibiotics including Florfenicol,Streptomycin,Tetracycline and etc.The result was:The resistance to Amoxicillin ranked top(100%),and others were Norfloxacin(95.24%),Tetracycline(95.24%),Doxycycline(95.24%),Ciprofloxacin (90.48%),Ciprofloxacin(90.48%),Ofloxacin(85.71%),Streptomycin(66.67%), Florfenicol(57.14),Erythromycin(47.62%),Neomycin(19.05%)and Amikacin(19.05%). These 21 strains showed various degree of drug resistance,and all of them are multidrug resistant,with 4 the least number of resistant drugs and 12 the most,8 in average.The isolates from different areas are sensitive to different antibotics:Strains isolated from Northeast are sensitive to Florfenicol,Neomycin and Amikacin;Strains from Hebei are sensitive to Gentamicin and Neomycin;Strains from Shandong are sensitive to Neomycin and Amikacin;Strains from Eastem China are resistant to 12 antibiotics.These results of antibiotics sensitivity test have provided evidence for clinical medication.3,ERIC-PCR genotyping of 21 avian pathogenic E.coli isolatesThe genomic DNA of 21 isolates were extracted and amplified by ERIC-PCR.The products obtained were analyzed with agarose gel electrophoresis,and then the ERIC finger print maps were made by cluster analysis.The genetic dendrogram showed that 21 E.coli strains are clustered into 9 ERIC genotypes(A,B,C,D,E,F,G,H,I),with D the main genotype(11 strains:3 from Northeast China,3 from Hebei,4 from Shandong;1 from Eastern China).The next genotype was E:1 strain each from Northeast,Shandong and Eastern China;Others were 1 each for 1 genotype.The relationship among ERIC-genotype,serotype and drug resistance spectrum was analyzed,and found there was no direct relationship between genotype and serotype or drug resistance spectrum.