Investigation And Analysis Of Cephalosporin Drug Resistance Of E.coli From Waterfowl In Different Breeding Modes

In order to explore the law of cephalosporin resistance of E.coli carried by waterfowl in different breeding modes(intensive,courtyard and field),200 strains of E.coli were isolated from fecal samples of waterfowl collected from Sichuan,Heilongjiang and Anhui in 2021.The investigation and analysis of cephalosporin resistance were carried out around these strains,and the epidemic spread of the main drug resistance genes in 2022 was detected.The main results are as follows:The prevalence of extended-spectrum β-lactamases(ESBLs)-resistant E.coli from waterfowl in different breeding modes:In 2021,80,80 and 40 of E.coli were isolated from waterfowl feces samples raised in mtensive,courtyard and outdoor breeding modes,respectively,a total of 200 strains.(1)The phenotype of ESBLs was detected by double disk diffusion method,and the total positive rate was 68.00%(136/200).The positive rates of intensive,courtyard and wild breeding models were 98.75%(79/80),36.25%(2980)and 70%(28/40),respectively.(2)The MIC test results of cefalotin cefoxitin,cefotaxime and cefepime showed that the resistance rates of intensive culture were 100.00%(80/80),38.75%(31/80),100.00%(80/80)and 100.00%(80/80),respectively.The drug resistance rates were 100.00%(80/80),40%(32/80),63.75%(51/80)and 45.00%(36/80),respectively.The resistance rates of outdoor aquaculture were 100.00%(40/40),52.50%(21/40),82.50%(33/40)and 77.50%(31/40),respectively.(3)PCR detection results of blaCTX-M,blaTEM,blaOXA and hlaSHV showed that the positive rates of intensive culture were 98.75%(79/80),71.25%(57/80),21.25%(17/80)and 0%(0/80),respectively.The positive rates of courtyard breeding were 55.00%(44/80),88.75%(71/80),6.25%(5/80)and 0%(0/80),respectively.The positive rates of drug resistance in outdoor breeding were 70.00%(28/40),47.50%(19/40),22.50%(9/40)and 0%(0/40),respectively.The detection rate of was the highest(75.50%,151/200),among which blaCTX-M-55 subtype accounted for 36.00%(72/200),followed by blanTEM(73.50%,147/200).Again blaOXA,15.50%(31/200):no E.coli carrying blaSHV.(4)All E.coli isolated in 2021 were not only resistant to one or more cephalosporin drugs,but also had high resistance rates to non-cephalosporin antibiotics such as tetracycline and gatifloxacin.2.The propagation characteristics of plasmid carrying blaCTX-M-55:A total of 58 strains containing blaCTM-M-55 subtype gene were screened from 200 strains of E.coli isolated in 2021,including 52 strains from intensive breeding mode.The blaCTX-M-55 subtype gene could be transferred to the recipient E.coli J53 by conjugation transfer test,and the recipient E.coli J53 obtained the ability to tolerate cephalosporins.The plasmid conjugation frequency of 58 strains carrying blaCTX-M-55 gene was between 10-3 and 10-2.The successfully conjugated plasmid could exist stably in the recipient bacteria for 10 days and the recipient bacteria showed no obvious adaptation cost.In the molecular typing of E.coli with conjugative transfer ability,it was found that blaCTX-M-55 gene was widely present in different phylogenetic groups and ST strains.In this study,27 ST types of E.coli were associated with blaCTX-M-55,of which 18 ST types were not reported.There were 195,60 and 55 of E.coli isolated from intensive,courtyard and outdoor breeding modes in 2022,correspondence 2021,respectively.The resistance genes blaCTX-M,blaTEM,blaOXA,blaSHV and subgroup blaCTX-M-1G were detected.The subtype blaCTX-M-55 accounted for 37.74%(117/310),it shows that there is a possibility of continuous and widespread transmission of blaCTX-M-55 in these waterfowl breeding places.In summary,the level of cephalosporin resistance of E.coli carried by waterfowl in intensive breeding mode was significantly higher than that in courtyard mode and outdoor mode,the blaCTX-M-55 subtype gene is the most prevalent resistance gene in this family,which can follow the plasmid through the conjugation transfer pathway and is plays a maj or role in promoting the spread of cephalosporin drug resistance.