| In order to understand the distribution of virulence genes, drug resistance and phylogenetic groups of dog-related E. coli in Chengdu area, the canine anal swab samples were collected for isolation and identification of E.coli. Thirteen kinds of related virulence genes of the clinical isolates were dected by PCR, and the susceptibility to commonly used antibiotics were determined. By using the established PCR methods, the main resistance genes for antibiotics, including β-lactams, quinolones, aminoglycosides, chloramphenicol and sulfonamides, were detected, and the coincidence rate between the resistant phenotypes and resistance genes were analysed.This study mainly achieved the following achievements:1. Total 156 strains of E. coli were isolated and identified from 175 canine anal swab samples. Among them, 104 isolates were isolated from clinically healthy dogs, and 52 isolates were isolated from diarrhea dogs, the total isolation rate was 89.14%. Serotypes identification for these strains showed that, canine E. coli serotypes distributed dispersedly and there was no significant dominant serotypes, Except the virulence gene cva C, the dection rates of fim C, sit A and omp T genes in isolates from clinical heathy and diarrhea dogs were all over 40%. Detection rates of iro N, tsh, iss and hly A genes in diarrhea isolates were significantly higher than the clinically healthy isolates, which inferred that incidence of E. coli disease in dogs may be related with the virulence genes carried in E.coli strains.2. The drug sensitivity to commonly used antibiotics were determined for 156 canine E. coli strains, in which, the strongest resistance were to cefquinome and lincomycin,which was 100% and 97.4% respectively, followed by ampicillin and amoxicillin reaching73.1% and 69.9% respectively, resistance to meropenem and colistin was lowest with 4.5%and 5.8% respectively. Resistance rates to other antibiotics were 20% to 60%.Multi-drug-resistant strains accounted for 95.51%(149/156), in which, 7-resistance wasthe largest proportion(12.18%, 19/156), followed by 9-resistant(10.90%, 17/156), 14-resistance(10.90%, 17/156), 10-resistance(9.62%, 15/156) and 5-resistance(8.33%,13/156).3. Seventeen categories in 5 kinds of drug resistance genes from 156 canine E.coli strains were detected by established PCR methods. The detection rates of β-lactams drug resistance genes blactx-m and blatem were the highest, which were 89.74% and 78.84%respectively, followed by the sulfonamides drug resistance gene, which was 63.46%, the detection rates of quinolone resistance gene aac(6′)-Ib、Oqx AB and qnr S were 18.59%,35.26% and 26.9% respectively. The detection rates of aminoglycoside resistance genes aad A、aac C2、aac C4 and aph A3 were 23.07%, 55.77%, 8.97% and 26.28% respectively.Comparesion of the coincidence rate of the resistance phenotypes and resistance genes showed that, the coincidence rates between the resistance phenotypes and resistance genes to mino glycosides, β-lactams, quinolones and chloramphenicols were high up to 81%,which were 89.15%, 100%, 81.31% and 91.42% respectively. This research detection results of the main resistant genes in canine E.coli for 5 kinds of antibiotics, includingβ-lactams, fluoroquinolones, amino glycoside and chloramphenicol sulfonamides, which enriches the epidemiology data of drug-resistant gene of canine E.coli.4. In order to furtherly understand the genetic origin and molecular characteristics of canine E.coli strains, triple PCR method was used to analyze the clinic phylogenetic groups. The results showed that, the E.coli strains were mainly distributed in group A(35.40%, 59/156), the second was in group D(29.49%, 46/156) and B1 group(20.51%,32/156), and the least was in group B2(12.18%, 19/15), in which, E.coli number in groups B2 and D accounted for 41.67%(65/156) of total. There was significant difference in drug resistance rate of the bacteria between the pathogenic groups(B2 and D) and commensal groups(A and B1)(P<0.05). Although virulence related genes of canine E.coli strains were distributed in every phylogenetic groups, the average number of virulence genes of group B2 was higher than that of other phylogenetic groups. |
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