| Dairy Cow Mastitis is a frequently encountered disease in dairy industry, and is also an important factor restricting development of dairy industry. The experiment collected 420 samples from seven areas in Hebei to examine the incidence of cow mastitis, using the combination of DHI data monitor and LMT. The Results showed that using DHI data monitor, 126 positive sampels were examined form 420 dairy cows with positive rate as 30%. And using LMT, 128 positive sampels were examined form 420 dairy cows with positive rate as 30.48%. Namely in this experiment the accordant rates of DHI data monitor and LMT reached 98.42%. The positive rate of Xingtai, Cangzhou, Langfang, Tangshan, Baoding, Shijiazhuang, Zhangjiakou were 35%, 28%, 24.44%, 28%, 30%, 27.14%, 33.33% respectively.Using the combination of microbiology and molecularbiology, the mastitis pathogenic bacteria were isolated, cultured and identified from the milk samples in the seven areas of He Bei province. Then isolated four main pathogenic bacteria,362 strains. The main pathogenic bacteria caused dairy cow mastitis were staphylococcus aureus, streptococcus agalactiae, escherichia coli and pseudomonas aeruginosa. Among them, 167 strains were staphylococcus aureus, accounting for 46% of total isolates, 94 strains were streptococcus agalactiae, accounting for 25.97% of total isolates, 84 strains were escherichia coli, accounting for 23% of total isolates,17 strains were pseudomonas aeruginosa, accounting for 5% of total isolates. And almost all the samples detected were mixed infection with staphylococcus aureus, streptococcus and escherichia coli. But the 17 strains of pseudomonas aeruginosa checked out all isolated from Zhangjiakou area milk sample, which were mied infection with four bacteria.This experiment consulted the K-B susceptibility paper method commended by NCCLS, conducted 15 kinds of drug sensitive tests for the four main isolated bacteria to detemine the size of bacteriostatic ring. The results showed that the pathogenic bacteria in the seven areas had a high sensitivity to cefotaxime, furazolidone, enrofloxacin, florfenicol and fosfomycin, while its resistance to kanamycin, azithromycin, tetracycline and ciprofloxacin were serious.All the strains were almost completely resistant to penicillin and streptomycin. All the strains are almost completely resistant to penicillin and streptomycin. According to the results of drug susceptibility,362 strains bacteria isolatated from seven areas of He Bei province existed multiple drug resistance, accounting for about 86.46% of all strains.The study used polymerase chain reaction(PCR) to investigate thee carry genes for resistance and the correlation between phenotypes and genotypes of dairy cow mastitis in He Bei province. The result showed that the drug-advantage of resistance genes detected from the staphylococcus aureus, streptococcus agalactiae, escherichia coli and pseudomonas aeruginosa were gyr A、erm B、qnr B and qnr B respectively. The accordant rates of the first three kinds of bacteria’s resistant phenotype and genotype were more than 85%, which indicated drug sensitive tests was accurate to guide clinic.After the drug test, DHI data suggested SCC level in September, October, November and December had significant difference(P < 0.01), and its decline was between 14.01% and 45%.Through the PCR amplification products from selecting the parts of pathogenic bacteria with gel extraction, sequencing and comparing with the related sequences in Gene Bank, then identified pathogenic bacteria species they belong to.To sum up, through the drug sensitive test and the detection of drug resistance genes, the study results would be feedback to the dairy farm to guide the clinical medication and breeding management. Meanwhile, it can provide theoretical basis t prevent and control the main pathogenic bacteria of dairy cow mastitis for different area in Hebei province. |
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