| Canine pyometra is a common disease in veterinary clinic and a great threat to the health of canine reproductive system. The objective of this study was to confirm the species of bacteria collected from canine pyometra, to compared the homology of uterine E. coli strains with intestinal E.coli, to study the distribution of the virulence factor and their drug resistance and to investigate the influence of E.coli strains with different virulences on inducing the CEH/P syndrome model and their virulences.Method:(1) The bacteria strains were routinely isolated and identified from the uterine contents which were collected from canine pyometra and preserved in low temperature refrigerator. The sequencings of 7 housekeeping genes of E.coli strains isolated from the pyometra cases and feces of healthy dogs were made by using a multilocus sequence typing (MLST) scheme, E.coli typings, hormology comparison and hormologic evolutionary trees were investigated in database; (2) PCR technology was applied to investigate the distribution of virulence genes and LD50 on mice was conducted to test the virulence of the E.coli strains and drug sensitive tests for 20 kinds of antibiotics according to E. coli strains wwere carried out as well; (3) 9 mixed breed bitches which were intact and not gestated were selected for inducting the experiment of the CEH/P syndrome model. Animals were divided into 3 groups,3 dogs for each group. One and two groups were designed for experimental groups and three was control group. First of all, ovariectomies were performed for experimental and control groups. Meanwhile, a silk suture was embeded in the left uterine horns of experimental groups.3-4 weeks after operation, the bitches were injected with estrogen and progesterone for simulating the estrus cycle.12 days after the bitches went into the stage of metaestrus, the E.coli strains with stronger virulences were inoculated into the uteruses of group 1 and the E.coli strains with weak virulences were inoculated into the uteruses of group 2. After successfully inducing the CEH/P syndrome model, bacteria were isolated from the uterine contents, and identified by MLST scheme for E. coli. And then the virulence of E.coli strains was detected using LD50 test on mice and compared with that before injecting E.coli into the uterines.Result:(1) pathogenic bacteria were isolated from 23 samples among 26 cases, no pathogenic bacteria was isolated from the other 3 samples.11 cases of E.coli (47.8%),5 cases of Staphylococcus (21.7%),3 cases of Klebsiella (13.0%),3 case of Streptococcus(13.0%), and 1 case of Pseudomonas aeruginosa(4.5%) were found with microscopic examination and biochemical test; Results of MLST indicated that the uterine E.coli strains had poor genetic relationship with the intestinal E.coli, but had close evolutionary relationship with uropathogenic E. coli(UPEC); (2) differences of virulence existed between strains of E.coli with varied virulence gene distributions and a strain with more virulence genes was comparatively more virulent; the isolated strains were relatively resistant to penicillin, oxacillin and erythromycin while comparatively susceptible to other drugs, especially aminoglycoside antibiotics and cephalosporin antibiotics; (3) all groups (1st and 2nd groups) of the CEH/P syndrome model induced by Ecoli strains were successful, which meant the influence of inducing the CEH/P syndrome model by using E.coli strains with different virulence was small, and the virulence was not the decisive factor; the most virulences of the E.coli strains isolated from the CEH/P syndrome model were enhanced, some of them were significant difference (P<0.05), but some are not (P >0.05) compared with that before the model test.In conclusion:(1) E. coli which is the dominant strain of canine pyometra has closer evolutionary relationship with UPEC than intestinal E.coli; (2) The number of virulent genes in E.coli may directly proportional to its virulence. Aminoglycoside antibiotics and cephalosporins antibiotics can be used for canine pyometra treatment caused by E. coli; (3) E.coli strains regardless of the virulence could induce the CEH/P syndrome models, and the virulence of most E.coli strains enhance slightly after the model test. |
PDF Full Text Request