First Insights Into Prevalence Of Antimicrobial Resistance And Resistance Genes In Faecal Escherichia Coli Isolates From Dogs

Apart from being commensals and playing an important role as intestinal pathogens,Escherichia coli are among the most common causative agents for urinary tract infections (UTI).With the widely use of beta-lactam antibiotics，the problem about resistance of bacterial isbecoming worse than before. As a cause of community-acquired infections,extended-spectrumβ-lactamase (ESBL)-producing E.coli constitute an emerging public-healthconcern. Few data on the molecular epidemiology of ESBL-producing E. coli isolates from petsare available in China.Companion animals such as dogs play an important role in the exchange of antimicrobialresistance determinants in bacterial populations, since they are exposed to antimicrobial agents(for treatment) similar to those used for humans. They also share the same environment ashumans and remain in close contact with them. Moreover, transmission of resistant bacteria ormobile resistance determinants between companion animals and humans has been documented.Since the first detection of an ESBL in an E.coli isolate from a laboratory dog in Japan in1998avariety of ESBLs, including CTX-M-type ESBLs, and pAmpCs have been reported for bacteriaderived from dogs, cats, and other companion animals worldwide. Thus, such bacterial strainsmay provide a reservoir for ESBL-and/or pAmpC-producing bacteria for humans. A furtherworrying development is that highly virulent human pandemic B2-O25:H4-ST131CTX-M-15producing E. coli strains were recently isolated from companion animals belonging to differentspecies in various European countries. The possibility of interspecies transmission of thesemultiresistant strains from humans to companion animals and vice versa is a matter of greatpublic health concern.A total of191anal swab samples were collected from dogs including59working dogs.E.coli were isolated and analyzed for phylogenetic groups and resistance to13antimicrobialagents. A total of254E. coli isolates were recovered from191anal swab samples of dogs. Theresults showed the E.coli isolates has higher resistant. Among canine E. coli isolates, they werehigher resistance to amikacin and ampicillin. Of187Escherichia coli isolates were multipleresistant (resistance to more than three kinds of antibiotics) and only8strains of E. coli did notshow any resistance to all13antimicrobial agents. The results shown that the drug resistancerate of E. coli strains isolated from pet dogs were higher than those from working dogs.A total of153extended-spectrum-cephalosporin-resistant E.coli strains isolated from dogswere investigated using molecular methods. Extended-spectrumβ-lactamase (ESBL) phenotypes were identified in132E. coli isolates. All107ESBL-producing isolates carried blaCTX-Mgenes. The most common CTX-M types were CTX-M-55(n=20) and CTX-M-79(n=19).Isolates producing CTX-M-3, CTX-M-123, CTX-M-15, and CTX-M-82were also identified.79ESBL-producing isolates carried blaTEM gene. The most common TEM types wereTEM-206(n=71) isolated from hospital dogs, and TEM-1(n=8) from working dogs. Theresistance gene of SHV was not detected., and detection of resistance gene of AmpC showedthat only three strains were positive.ISEcp1U1was identified in the upstream region of88out of the107blaCTX-Mgenes.Meanwhile the number of36in this strains carrying ISEcp1U2. In blaCTX-Mgenes downstream,they were detected carry ing IS903(n=50) and orf477(n=60) out of the107blaCTX-Mgenes. Atthe same time they has10strains carryed these four the gene for the detection. It is suggestedthat the horizontal transfer of blaCTX-Mgenes, mediated by mobile elements, contributes to theirdissemination among E. coli isolates from pets.To investigate the location of genes encoding ESBLs, plasmid typing and transductionexperiments transconjugants from55strains were obtained by conjugation experiments usingE.coliJ53. The rates of conjugation transfer were41.82％in55ESBL-producers, ESBLsproduction of all transconjugants were detected by CLSI Confirmatory Test.The studies haveshown that strains producing ESBLs can be transferred by way of horizontal transmission. Thetransconjugants were highly resistant to cephalosporins just same as their donor strain. Mostgene-carrying plasmids bearing resistant genes to other antibiotics at the same time, thenbecome multi-resistant, the resistance gene to non-β-lactams can be cotransferred with the ESBLbearing plasmid. In conclusion,86%(132/153) Escherichia coil isolations separated from dogspossess extensive ESBL drug resistance which is rather sever and wide-spectrumed.Conjectionassays indicates that the resistance genes,CTX-M,in Escherichia coil isolated from dogs cantransfer across species,with an incidence of41.82%(23/25). This investigation pose a greatsignificance of public health on controling of the transmission of drug-resistance bacteria andtheir genes of companion animals.