| Escherichia coli is an important pathogen causing dairy cow mastitis.In recent years,the incidence of dairy cow mastitis caused by this bacterial infection is on the rise.In addition,due to the irregular use of antibiotics in the treatment process,the drug resistance of Escherichia coli mastitis in dairy cows is prominent,and research on the prevention and control of the bacteria is urgently needed.The southern Xinjiang region is an important dairy farming area.In order to further understand the epidemiological characteristics and drug resistance of Escherichia coli originating from dairy cows in this area,and to explore possible prevention and control methods,this study carried out the following studies:1.Isolation,identification and drug resistance monitoring of Escherichia coli from dairy cows in southern XinjiangIn order to understand the molecular epidemiology of Escherichia coli mastitis in dairy cows in southern Xinjiang,this study conducted drug susceptibility experiments and phylogenetic group studies on 126 strains of Escherichia coli mastitis isolated and identified from four dairy farms in the region from 2019 to 2021.It showed that the isolation rate of Escherichia coli mastitis in dairy cows in this area was 40.5%.The drug susceptibility test results of the isolated strains showed that the antibiotic resistance rates of the isolated strains were: tetracycline(42.9%),streptomycin(34.5%),cefradine(30.3%),cotrimoxazole(28.6%),Ampicillin(26.9%),gentamicin(21%);the isolates were sensitive to amoxicillin-clavulanate potassium and polymyxin B;the multidrug resistance analysis of the isolates showed that about 1 /3 of the resistant strains were shown to be multi-drug resistant(MDR).The results of the phylogenetic group test of the isolated strains showed that the symbiotic groups A and B1 accounted for 85.8% of the total isolates,and the phylogenetic group D group and B2 group accounted for 11.1% and 3.2%,respectively.2.Detection of Escherichia coli resistance gene and ESBL(Extended Spectrum β-amidase)in dairy cows in southern XinjiangIn order to detect the drug resistance genes of the isolated strains,11 drug resistance genes(CTX-M,Amp C,tet A,TEM,SHV,KCP,tet B,acr A,acr B,OXA,tet-C)were selected in this study.Three triple PCR assays and one double PCR assay were established.Using the established PCR detection method for drug resistance genes,126 isolated strains of Escherichia coli were tested for drug resistance genes.The detection results showed that the detection rates of Amp C,TEM and acr A were 99.2%,99.2% and 92.9% respectively,followed by The detection rate of tetracycline resistance genes in tet A and tet B was 18.3%,and SHV,KCP,OXA and tet-C were not detected in all isolates.Enzyme inhibitor enhancement test was performed on all 10 strains of CTX-M and 15 strains of TEM + Amp C mastitis Escherichia coli,and the results showed that CTX-M was strongly correlated with ESBL,while the combination of TEM and Amp C did not detect positive and did not produce Extended-spectrum beta-lactamase.All 10 CTX-M and 15 TEM + Amp C strains of Escherichia coli,mastitis were tested for biofilm,and the results showed that the positive strains of ESBL enzyme inhibitor test had stronger biofilm formation ability than the negative strains.3.Research on prevention and control technology of dairy cow mastitis-derived Escherichia coli based on probiotics and Itaconic acidIn order to screen products that can be used for the prevention and control of dairy cow mastitisderived Escherichia coli,six strains of probiotics including Bacillus licheniformis,Bacillus paralicheniformis,Lactobacillus brucei,Lactobacillus rumen,Bacillus subtilis,and Lactobacillus weissii were isolated and verified in this study.Inhibitory effect of its lysate and supernatant on isolated strains.The results showed that the lysates and supernatants of the 6 strains of probiotics had no significant inhibitory effect on Escherichia coli mastitis.Itaconic acid and its derivatives play important roles in antibacterial,anti-inflammatory,antitumor,etc.In order to verify whether itaconic acid has a synergistic effect with the most resistant tetracycline in the prevention and control of dairy cow mastitis-derived Escherichia coli,this study Different concentrations of itaconic acid and tetracycline were selected to be used in combination to verify the bacteriostatic effect on the isolates.Escherichia coli has no inhibitory effect,but the combination of 75 mmol/L and 25 mmol/L itaconic acid and 25 mg/m L tetracycline has a synergistic effect,which can significantly inhibit mastitis-derived Escherichia coli.The results of this study showed that the isolation rate of Escherichia coli from dairy cows in southern Xinjiang was 40.5%.The isolated strains had a high multidrug resistance rate,high detection rates of drug resistance genes Amp C,TEM and acr A.CTX-M and ESBL showed strong Correlation,and ESBL strains have stronger biofilm formation ability.The combined use of itaconic acid and tetracycline can effectively improve the inhibitory effect on the isolated strains.This study can provide a reference for the prevention and control of Escherichia coli from dairy cows in southern Xinjiang. |
PDF Full Text Request