Antimicrobial Resistance And Virulence Of Escherichia Coli From Dogs And Cats In Northeastern China

With the widespread use of antibiotics,the emergence and spread of bacterial resistance has led to serious public health problems.Current studies related to antibiotic resistance in animal-derived were focused more on food-origin animals,such as livestock and poultry.Due to their close contact with humans,companion animals should be more concerned about their risk of transmitting zoonotic pathogens.Escherichia coli（E.coli）is an important component of the intestinal flora and an important model organism for studying genetic variation in bacterial virulence and drug resistance.E.coli can become zoonotic pathogens through horizontal transmission of multiple mobile genetic elements carrying heterologous genes,thus posing potential threats to human health.This thesis aimed to analyze the transmission and epidemiological patterns of multiple virulence and multidrug-resistant E.coli in dogs and cats through phenotypic identification,genotypic determination and molecular epidemiological studies.In this thesis,609 fecal or anal swab samples from dogs and cats were collected from Northeast China in 2021,and the samples were separated and purified.Specific E.coli 16S r DNA primers were used to identify the isolates.A total of 368 E.coli were isolated,with the isolation rate of 60.43%.The BD Phoenix-100?automatic microbiological identification/drug susceptibility system was used to test resistance phenotypes of E.coli.The results showed that 84.51%（311/368）were resistant to antibiotics,1.90%（7/368）were resistant to colistin,and 1.90%（7/368）were resistant to carbapenem among E.coli strains.68.75%（253/368）of E.coli were multidrug-resistant E.coli（MDR-E.coli）.41.03%（151/368）of E.coli were ESBLs producers.The isolation rates of ESBLs-E.coli in pet dogs,working dogs and pet cats were 38.22%,34.29%and 60.56%,respectively.The phylogroups of isolates were identified according to the multiplex PCR technology.Phylogroups A（37.77%）and B1（30.16%）were the dominant groups among E.coli isolates.Phylogroups A and B1were the dominant groups of canine E.coli,however,phylogroups B2 and B1 were the dominant groups in E.coli from companion cats.All ESBLs-E.coli were screened for 26 antibiotic resistance genes.The bla _CTX-M and bla _CTX-M+TEM were dominant among the ESBL producers.Except for qnr A,qnr C and tet（X1）～tet（X5）,the other tested genes were detected.The aac（3）-II had the highest detection rate among aminoglycoside resistance genes,reaching 46.12%.The sul2 had the highest detection rate among sulfonamide resistance genes,reaching 60.27%.The flo R had the highest detection rate among chloramphenicol resistance genes,reaching 43.38%.The qnr S had the highest detection rate among quinolone resistance genes,reaching 28.77%.The tet（A）had the highest detection rate among the tetracycline resistance genes,reaching 70.78%.The detection of bla _NDM,bla _KPC,bla _IMP or mcr-1～mcr-5 for carbapenem or colistin resistant E.coli showed that 42.68%of E.coli carried bla _NDM and 100%of E.coli carried mcr-1.A total of 156 E.coli strains were selected for short-read whole-genome sequencing（WGS）based on isolation information,non-clonal strains,different phylogroups and antimicrobial phenotypic to analyze their epidemic characteristics of virulence genes,serotypes,drug resistance genes,plasmid types and ST types.The detection rates of commensal and pathogenic E.coli were 53.21%and 46.79%,respectively.34.62%（54/156）of E.coli were uropathogentic E.coli（UPEC）or extraintestinal pathogetic E.coli（Ex PEC）,the rest were intestinal pathogenic E.coli（In PEC）and heterozygotes.Most of Ex PEC/UPEC were isolated from healthy samples.Phylogroup B2 was the dominant group（38.89%）in Ex PEC/UPEC and phylogroup A was the dominant group（47.62%）in In PEC and its heterozygotes.The serotypes were scattered,with no major dominant serotype.bla _CTX-M-55 and bla _CTX-M-14 were the main bla _CTX-M prevalent subtypes.95.51%（149/156）of E.coli carry one or more plasmids,and only 4.48%（7/156）did not carry any type of plasmid.Inc FIB had the highest detection rate,followed by Inc FII,Inc I and Inc FIC.The main ST types were ST10,ST155,ST744,ST117,ST457,ST101,ST127,ST73.In conclusion,the monitoring of drug resistance and virulence of isolations of canine and feline origin revealed that E.coli resistance was serious,and the issue of high prevalence of ESBLs-E.coli belonging to group B2 in fecal samples from pet cats deserved further investigation.The high detection rate and high resistance rate of feline pathogenic E.coli should not be underestimated,and feline feces might be an important reservoir for multi-drug resistant UPEC infections in humans.The public health risk of dogs and cats carrying multi-drug resistant zoonotic pathogens remains a continuing concern because they are in close contact with humans.