Isolation,Identification And Pathogenicity Of Mycoplasma Bovis In Southern Xinjiang

Mycoplasma bovis is a pathogen that is difficult to eradicate.It can cause pneumonia,mastitis,arthritis,otitis media,corneal conjunctivitis,meningitis,endocarditis and other diseases.It is widely spread all over the world and has caused huge losses.Mycoplasma bovis infection has been reported in most provinces of China.Mycoplasma bovis infection is more serious in southern Xinjiang.At present,there is no generally effective Mycoplasma bovis vaccine and the pathogenesis is still unknown.It is necessary to provide Mycoplasma bovis field strains and detect the growth characteristics and pathogenicity for the follow-up research and development of Mycoplasma bovis vaccine and related research.In this study,relevant samples were collected in southern Xinjiang,and PPLO medium was used for separation and purification,PCR detection,sequencing analysis,staining microscopy,growth characteristics detection,drug sensitivity test and infection test to obtain experimental data,so as to provide some reference for follow-up research and clinical diagnosis and treatment.The results showed that 22 strains of mycoplasma isolated from the solid and decocted medium had the characteristics of"clear"and"yellow"in the liquid medium;After sequencing,three isolates with low homology and distant genetic relationship were selected for follow-up test;The homology between the three strains of Mycoplasma bovis was 98.2%-98.5%,and98.6%-99.0%with the standard strain pg45 of Mycoplasma bovis;In the evolutionary tree,the isolate is in the same branch as other Mycoplasma bovis isolates,of which isolate 1 has the closest homology with kg4397;Isolate 2 had the closest homology with cq-w70 and kg4397;Isolate 3 has the closest homology with nm2012.Mycoplasma bovis colonies and bacteria were stained by gram and Giemsa staining.After Gram staining,Mycoplasma bovis colonies and bacteria showed yellow,but it was difficult to find bacteria under 1000x microscope,and the staining effect was poor;Giemsa staining showed blue under 1000x microscope,and the dyeing effect was good.After the growth curve was detected by CCU,the growth rate of the three strains of Mycoplasma bovis was slightly different,which could reach 10~9 CCU/m L.In the drug sensitivity test,the three isolates were not sensitive to erythromycin,azithromycin,tetracycline,polymyxin B and compound sulfamethoxazole;On the whole,it was sensitive to amikacin,minocycline,doxycycline,florfenicol,clindamycin,levofloxacin and ciprofloxacin;Among them,isolate 1 showed obvious drug resistance.The results of infection test showed that Mycoplasma bovis had certain pathogenicity tochicken embryo,which could affect the growth and development of chicken embryo and cause the death of chicken embryo.The existence of Mycoplasma bovis was detected by PCR detection and isolation in the allantoic cavity of chicken embryo.In terms of pathogenicity,isolate 1 showed stronger virulence than isolates 2 and 3 in lethality(20%),urate deposition rate(30%)and average body weight(9.50g),but they were all weak strains.In the pathogenicity of mice,the body weight,body temperature and lungs of mice after challenge were consistent with those of the control group.The presence of Mycoplasma bovis was not found by PCR detection and pathogen isolation.At present,mice are not suitable for Mycoplasma bovis infection model.