Study On The Antimicrobial Resistance Of Escherichia Coli In Swine Origin And The Transmission Of ESBL Genes By Plasmids

Escherichia coli(E.coli)is one of the most common zoonotic pathogens,and a constant threaten to human and animal health.Especially,more and more pathogenic isolates show multidrug-resistance,which may related with the world widely use of antimicrobial agents in veterinary medicine.In this thesis,E.coli were isolate from pig farms in northwestern China.The drug resistant spectrum of those bacteria isolates were analyzed and also the type of the harboring-plasmids.We abstained the following results:1.A total of 174 strains of cefotaxime resistant E.coli were isolated from 400 pig faecal samples collected from Gansu,Shaanxi,and Ningxia provinces,among which 82 isolates in total were able to transmit their drug-resistance genes though plasmids by conjugation experiments,with a plasmid transfer rate of 47.1%.The prevalent β-lactamases of these E.coli strains were mainly belonging to CTX-M-1 group,CTX-M-9 group,and TEM,with the highest carrier rate in the CTX-M-1 group.2.The ESBLs-producing strains isolated are highly resistant and have a broad spectrum resistance profile.The resistance rate to ampicillin antibiotics were up to 100%,yet,the lowest rates were 7.4% and 12.4% corresponding to fosfomycin and imipenem,respectively.In addition,the multi-locus sequence typing(MLST)of the E.coli collected were relatively scattered and no trend of concentrated epidemic.3.A total of 10 plasmid types were detected in the 82 ESBLs-producing E.coli strains from pigs.Among them,IncFIB,Inc Frep,IncY,IncI1,and IncP types are the majorities with a rate of 31.7%,31.7%,23.2%,19.3% and 9.5%,respectively.Virulence genes were uncommon with a very low detection level.In summary,we collected 174 E.coli from pig farms in Northwest China and analyzed their molecular epidemiological characteristics.We revealed a relationship between the spread of ESBLs genes and the distribution of the resistant gene carrying plasmids in different districts.This provided useful information for prevention epidemic and trace the source of the ESBL genes,and also for clinical antibiotic use to control the related diseases.