Isolation,Identification And Drug Resistance Analysis Of Cow Mastitis In Nantong Area

Dairy cow mastitis is one of the most serious diseases in the dairy farming industry.In recent years,the dairy farming industry in Nantong region has developed healthfully,but the competition in the industry is also increasingly intensified.Therefore,it is particularly urgent to study the epidemiology and prevention and control measures of mastitis.In this study,milk samples were collected from 6 dairy farms in various counties and districts of Nantong City for the isolation and identification of pathogenic bacteria,epidemiological investigation,and drug resistance analysis of main pathogenic Staphylococcus aureus and Streptococcus,so as to provide reasonable suggestions for the prevention and control of dairy cow mastitis.1.Epidemiological investigation of cow mastitis in Nantong areaIn order to understand the incidence of cow mastitis in Nantong area and analyze the etiology,this study collected 282 milk samples with positive BMT test in some dairy farms in Nantong area.Among them,163 milk samples were detected as bacteria.175 strains were isolated by traditional isolation methods,including 102 strains of Staphylococcus,with a detection rate of 36.17%.The positive rate of 56 strains of Streptococcus was 19.86%.The detection rate of 17 strains of bacilli was 6.02%.The results showed that the main pathogens of cow mastitis in Nantong area were staphylococcus and streptococcus,and a few were caused by bacilli.2.Drug resistance analysis of Staphylococcus and Streptococcus isolates from cow mastitis in Nantong areaIn order to effectively treat dairy cow mastitis in Nantong area,the paper method was used to analyze the drug sensitivity of the main isolates Staphylococcus and Streptococcus.Resistance to 20 different antibiotics was tested using a wafer diffusion method,as recommended by the CLSI.In this experiment,102 strains of Staphylococcus showed the highest resistance to penicillin G,up to 61.76%,which may be related to the large-scale and frequent use of this drug in clinical treatment of mastitis.In addition,Staphylococcus also developed high resistance to polymyxin B(50%),tetracycline(41.18%),ceftazidime(38.24%)and macromycin(35.29%).In this study,the high antibiotic sensitivity rate of Streptococcus isolates was calculated,and the results showed that:The high sensitivity rates of ceftriaxone and ceftazidime were 91%and 87.5%,respectively;the high sensitivity rates of vancomycin,erythromycin,clarithromycin,fosfomycin and clindamycin were 84%,82%,73%,93%and 82%,respectively;the high sensitivity rates of phenoxacillin and furantoin were 84%and 82%,respectively;and the high sensitivity rates of levfloxacin were 82%.The results of a series of drug sensitivity tests showed that there was a strong antibiotic resistance in the treatment of cow mastitis in Nantong area.The use of antibiotics in the future should be improved to prevent the further deterioration of the resistance trend.3.Establishment and application of real-time PCR method for detection of drug resistance genes tetK and tetMIn order to understand the causes of increasingly serious tetracycline resistance,this paper established a real-time PCR method for detection of tetK and tetM genes.First of all,we designed two pairs of primers according to the sequences of these two genes in GenBank.At the same time,115bp fragments of them were intercepted and the whole gene of IDT company was synthesized and cloned into the vector as the control.The results show that the method established in this study is easy to operate and fast to detect.Two drug-resistant genes,tetK and tetM,were amplified specifically,and there was no cross reaction with other major genes of bacteria,showing strong specificity.The real-time PCR method for tetK and tetM,two drug-resistant genes of bacteria established in this study,provides a rapid,specific and sensitive technical means for the rapid detection of drug-resistant bacteria carried or contaminated in clinical animal and plant products,the detection of tetK and tetM nucleic acids in clinical samples and the epidemiological investigation.The method was applied to the detection of tetK and tetM of 102 strains of Staphylococcus and 56 strains of Streptococcus isolated in this study,and the results showed that a total of 50 strains of bacteria were detected to carry one or both of the two drug resistance genes.The results of this study suggest that the emergence of increasingly severe tetracycline resistant strains may be related to the relative drug resistance genes.