| Escherichia coli (E.coli) is one of the most common pathogen in medical and veterinary clinic and causes many diseases of person and livestock. It often causes severe diarrhea and sepsis in young animals, pig edema disease, human hemorrhagic colitis-hemolytic uremic syndrome, neonatal meningitis and nephritis and other diseases. With the extensive and abuse application of antimicrobials, Escherichia coli is resistant to many antimicrobials and has brought multiple drug resistance, which is serious clinical problem of anti-infective treatment of the veterinary. Therefore, it’s very important to analyze antimicrobials resistance and study on the molecular epidemiology of its resistance not only for disease prevention caused by Escherichia coli but also for monitoring the development and spread of resistant strains.By microbiological and molecular biological methods, Escherichia coli were separated and identified from the samples of clinical and subclinical bovine mastitis, which were collected from the NingXia cow farms. Antibacterial drug sensitivity test was carried out by disk diffusion method recommended CLSI and the advantages serotypes were identified by the method of plate agglutination. The virulence genes and resistance genes were detected by PCR. The main results are as follows:1. Escherichia coli were separated and identified from the samples of clinical and subclinical bovine mastitis, which were collected from the NingXia cow farm in 2011 to 2013.197 strains of E. coli have been identified by lots of methods, such as the chromogenic medium E.coli bacteria colony morphology, gram staining microscopy and 16S rDNA PCR amplification.2. According to relevant literature reported, choosing 38 kinds of E.coli 0 antigen, the 197 strains 0 antigen serum of mastitis in dairy cows were examined. The results showed that the serotype were identified in 138 strains, the 0127 (35/138), O158 (16/138) and 044 (12/138) wew superiority serotype. Six strains were self-curing and 53 strains were not identified.3. The sensitivity test of 16 antimicrobial drugs to 197 E.coli was carried out. The results showed that the E.coli had the highest resistance to ampicillin; the rate of resistance was 54.6%. In addition, they also had high drug resistance for doxycycline (39.59%), tetracycline (39.09%) and streptomycin (38.58%). On the contrary, the E.coli was sensitive to cephalosporins, polymyxin, fluorine benzene nicol, and quinolones and the sensitive rate was above 60%. All isolates tolerated up to 15 kinds of antimicrobial drugs.4. The virulence genes and resistance genes of 197 Escherichia coli were detected. The results showed that virulence genes, such as astA, eaeA, hlyA, escV, sepA and resistant genes, such as tetB, tetC, GyrA, GyrB and ParC were checked out. The detection rate of astA was 21.13%. The detection rate of hlyA was the lowest, only 1.02%. The positive rates of the resistant genes tetC and tetB in Tetracycline were 14.72% and 7.61% respectively. The detection rates of resistance gene GyrA, GyrB and ParC in Fluoroquinolone were 97.46%,98.98% and 98.48%, respectively.In conclusion, we analysed the drug resistance of Escherichia coli isolated from the NingXia cow farms and detected the resistance genes and virulence genes. It revealed the resistance and the prevalence of virulence genes of Escherichia coli isolated from bovine mastitis in NingXia and provide theory basis for using antimicrobials rationally and preventing and controlling the spread of drug-resistant pathogen and resistant genes. |
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