Research On Biological Characteristics Of Actinobacillus Pleuropneumoniae And Drug Resistance Genes Of Tetracycline Adapted Strains

Actinobacillus pleuropneumoniae(APP)is a pathogenic bacterium that can cause respiratory diseases such as pleurisy and pneumonia in pigs,and its transmission is mainly through air and direct contact.The main symptoms are acute bleeding and chronic fibrinous necrotizing pleurisy lesions.After infection,the pathogen can be colonized in the nasal cavity,respiratory epithelial cells and tonsils,causing persistent infection.It is one of the important infectious diseases which seriously affect the pig industry and cause great economic loss to the production efficiency of the pig farm.The biological characteristics of different serotype APP maternal strains and artificially induced drug-resistant strains were studied,and the drug-resistance correlation of drug-resistant strains was analyzed and explored.Specific contents and results are as follows:The results showed that the strains with different serotypes of APP grew better in BHI and TSB than in MHB,LB and PPLO.The results showed that the biofilm formation ability of the serotype 3,4,7 and 12 maternal strains was stronger,which indicated that the strength of biofilm formation was not positively correlated with the growth of bacteria.Drug sensitivity results showed that APP strains with different serotypes were sensitive to a variety of antibiotics.The growth of APP1-TET and APP7-TET was lower than that of the maternal strains APP1-WT and APP7-WT.Biofilm formation capacity increased by more than 2 times;The drug resistance of APP1-TET changed,and the drug resistance to tetracycline and penicillins increased significantly,and the MIC value increased from 0.3125 ?g/ mL to 10 ?g/ mL.The MIC value increased from 10 ?g/ m L to 40?g/ m L.The MIC value of aminoglycoside antibiotics decreased from 40 ?g/ m L to10 ?g/ m L.The resistance of APP7-TET to lincomycin increased significantly,and the MIC value increased from 10 ?g/ m L to 80 ?g/ m L,but the sensitivity of APP7-TET to penicillin decreased,and the MIC value decreased from 80 ?g/ m L to 10 ?g/ m L.The results of APX toxin secretion showed that the tetracycline resistant strain Apx toxin secretion was significantly reduced by the parent strain.Through the analysis of transcriptome sequencing results,10drug-resistance related genes with significant differences in expression were screened out.The q RT-PCR results showed that the transcription of Sap B,Sap C,Sap D,AIr,Ami ABC,Cpx A and Dsb A were down-regulated,and the transcription of Sap B,Sap C and Sap D were down-regulated significantly,while the transcription of Sap A,acr R and Cpx R were slightly up-regulated.The experimental results are consistent with the data analysis.The study of this topic provides reference for the analysis of the biological characteristics of APP strains with different serotype in different media and the molecular mechanism of drug resistance of tetracycline resistant adaptive strains,and lays an important molecular foundation for the prevention and treatment of drug resistant Actinobacillus pleuropneumoniae.