| Escherichia coli(E.coli)is one of the most common intestinal microorganisms in humans and animals,which can cause gastrointestinal tract infection in humans and many animals under special conditions,threatening the health of both humans and animals.E.coli is considered to be a repository of multiple drug resistance genes and an important place for gene exchange.The extensive clinical use of antibiotics in small animals has led to the gradual enhancement of antibiotic resistance of E.coli,which has aroused widespread concern around the world.As companion animals,pet dogs are in close contact with humans,which greatly increases the risk of E.coli transmission between dogs and humans.In this study,135 canine E.coli strains from Chengdu area were tested for antibiotic resistance phenotypes and antibiotic resistance genes(ARGs),and the correlation between antibiotic resistance phenotypes and antibiotic resistance genes,as well as among ARGs was analyzed.This study explored the association between antibiotic resistance and strain population structure by multi-locus sequence typing of multi-drug resistant(MDR)E.coli strains by multi-locus sequence typing(MLST).This study aims to understand the prevalence of antibiotic resistance of canine E.coli in Chengdu area and provide theoretical basis for guiding clinical drug use and monitoring antibiotic resistance in pet dogs.Moreover,this study further protect the common health of humans and animals as well as environmental biosecurity.In this study,170 samples of feces or anal swabs from canines with diarrhea were collected from several pet hospitals in Chengdu,and 135 strains of E.coli were isolated and identified.The isolates were tested for antibiotic sensitivity and antibiotic resistance genes.The results showed that the highest antibiotic resistance rate of isolates was β-lactam antibiotics(76.30%,103/135),and the antibiotic resistance rate to AMP was the highest(71.11%,96/135),followed by tetracycline(64.44%,87/135),sulfonamides(59.26%,80/135),aminoglycosides(33.33%,45/135)and amide alcohols(30.37%,41/135).The resistance rate to fluoroquinolone antibiotics was the lowest,which was(25.93%,35/135).Among 135 E.coli isolates,74(54.81%)isolates showed multiple antibiotic resistance.A total of 12 kinds of antibiotic resistance genes in 6categories were detected,and the highest detection rate was tetracycline resistance gene tet A.Both MDR and N-MDR had low detection rates of sulfonamide resistance genes sul3 and quinolone resistance genes oqx AB.The MDR had the lowest detection rate of oqx AB(16.22%,12/74),while the N-MDR had the lowest detection rate of sul3(11.48%,7/61).Futher,the correlation coefficient r value in Rstudio was used to analyze the correlation between antibiotic resistant phenotype and antibiotic resistant genes of canine E.coli.The results showed that there was a significant correlation(P<0.05)between antibiotic resistance phenotype and antibiotic resistance genes in canine E.coli.A total of 23 pairs showed positive correlation in MDR,among which the aminoalcohol resistance gene flor had strongly positive association with C.The aminoglycoside resistance genes aac C2 had strongly positive association with CN and aac C4 had strongly positive association with AMC.However,there were only two pairs of positive correlations between antibiotic resistance phenotypes and antibiotic resistance genes in N-MDR,which were aminoglycoside resistance gene aac C4 and DOX,AMC.In addition,there was also a significant correlation(P<0.05)among antibiotic resistance genes carried by canine E.coli.A total of 11 pairs of antibiotic resistance genes in MDR showed positive correlations(r>0),and sulfonamide resistance gene sul3 showed the strongest correlation with amide alcohol resistance gene cml A(r=0.46).Only fluoroquinolone resistance gene oqx AB had negative correlation with aminoglycoside resistance gene aac C4(r<0).In N-MDR,no antibiotic resistance gene pairs showed significant negative correlation,but 35 pairs showed significant positive correlation.Sul3 and cml A showed the strongest correlation(r=0.77),which was consistent with the result in MDR.Finally,this study used multilocus sequence typing(MLST)to classify 74 strains of MDR E.coli into 42 different STs,including 2 new STs(n ST1 and n ST2).The number of ST10 isolates was the largest,accounting for 14.86%.The 42 STs could be divided into 6 clonal complexes(CC)and 23 scattered distribution.Among the CCs,ST-10 CC had the most STs(ST10,ST44,ST175,ST744,ST1415,ST2197),accounting for 20.69% of the total STs.The detection rate of 6 types of antibiotic resistance genes in ST-10 CC ranged from 18.0% to 30.0%,which was higher than that in other CCs,and the detection rate of amide alcohol resistance genes was the highest(27.59%).This study showed that canine E.coli in Chengdu area had serious antibiotic resistance.The isolates were resistant to a variety of antibiotics and carried a variety of antibiotic resistance genes.There was a significant correlation between antibiotic resistance phenotype and antibiotic resistance genes,mainly positive correlation.54.81%of the isolates showed multi-drug resistance,and the ST types of MDR strains were scattered and diversified,showing an epidemic trend of ST10 and ST-10 CC. |
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