Molecular Detection And Biological Characteristics Of Pasteurella Isolated From Calf Respiratory Tract In Xinjiang

Objective:Pasteurella is an important pathogen of livestock and poultry,which can cause acute and chronic infections in many animals and bring certain economic losses to the global aquaculture industry.However,the biological characteristics of Pasteurella in respiratory tract,the difference and the relationship between Pasteurella and Pasteurella causing death have not been systematically reported.Therefore,on the basis of field epidemiology of 13large-scale farms in southern and northern Xinjiang,Pasteurella nucleic acid of 515 nasal swabs from calves respiratory tract were detected by PCR,the serotype,ST type,the characteristics of pathogenicity and drug resistance of isolates were analyzed,which provided meaningful data for the traceability,effective prevention and control,epidemiological study of Pasteurellosis in calvesMethods:(1)Molecular detection of Pasteurella from respiratory in calves:Field epidemiological investigation was conducted by field testing,record retrieval and field investigation,etc.in 13 farms in northern and southern Xin Jiang;PCR based on the specific kmt was used to detect Pasteurella nucleic acid in samples,the positive detection rate of Pasteurella was analyzed in calves of some large-scale farms in Xinjiang.(2)Isolation,identification and typing of Pasteurella from calf respiratory tract:Pasteurella were isolated from PCR positive nasal swabs,identified by biochemical experiment and specific kmt gene and 16S rRNA sequence analysis.Capsular typing,lipopolysaccharide typing and MLST typing of the isolates were detected and the relationship among them were analyzed.(3)Detection and analysis of virulence genes,drug-resistant genes and drug-resistant phenotypes of isolates from respiratory tract of calves;PCR was used to detect the main virulence genes and drug-resistant genes,micro broth dilution method was carried to analyze the drug-resistant phenotypes of the isolates,animal infection experiments were carried out in order to identified the pathogenicity,which were compared with the corresponding characteristics of Pasteurella causing infection.Results:(1)The level of feeding and management,the history of Pasteurella and epi demiology were affected the detection rate of Pasteurella in 13 large-scale farms in n orthern and southern Xinjiang.88 of 515 nasal swabs were PCR positive,the positive rate was 17.09%(88/515).(2)58 Pasteurella multocida were isolated from 88 positi ve nasal swabs,the isolation rate was 65.91%(58/88).The isolated strains were Past eurella multilaboides by 16S rRNA sequence analysis.The main capsule serotypes:LPS serotypes:ST type of Pasteurella multocida was A:L3:ST1.(3)The isolates had obviou s pathogenicity,and the preliminary study showed that the isolates(Pm97,Pm78)had high pa thogenicity.The pulmonary histological observation showed alveolar congestion,inflammator y exudation,alveolar fusion and lung interstitial widening;The carrying rate of 2 virulence genes(psl,tbp A)of 58 strains was 100%,no hgbB,toxA gene was detected.The isolates had the highest resistance to nalidixic acid,followed by sulfamethoxazole,chl oramphenicol and polymyxin E.The carrying rate of?-lactam bla _TEMgens was 18.97%(11/58),and no aminoglycosides,tetracyclines and polypeptide resistance genes we re detectedConclusion:The detection rate of respiratory Pasteurella multocida in calves in Xinjiang was high.The serotypes of the isolated strains were mostly A:L3,and the MLST type was relatively single.The strains carried abundant virulence factor genes and drug resistance genes,the drug resistance rate was high and the multiple drug resistance rates were common.Conclusion:The detection rate of Pasteurella multocida isolated from calf respiratory tract in Xinjiang was high,and the capsular serotype and lipopolysaccharide type of Pasteurella multocida isolated from calf respiratory tract were different from those of Pasteurella multocida causing death;MLST type of Pasteurella multocida isolated from calf respiratory tract was single.The virulence genes of Pasteurella multocida isolates were different from those of Pasteurella multocida isolates in iron uptake related genes and sialate kinase related genes;the isolates and Pasteurella multocida isolates were more resistant to quinolones and sulfonamides.