Study On The Efficacy Of Cinnamaldehyde On Goat-derived Pasteurella Multocidal And Pseudomonas Aeruginosa Pneumonia

A large number of animals die every year due to respiratory diseases and lack of effective treatment,which results in breeding losses and seriously impacts the development of the industry.Bacterial pneumonia is frequent that Pasteurella multocida and Pseudomonas aeruginosa are pathogenic bacteria of sheep respiratory diseases,which are usually treated with antibiotics clinically.However,systemic and long-term use of high-dose antibiotics may lead to serious negative impacts and antimicrobial resistance problems are increasing.Therefore,there is a clinical need for low-toxicity,effective,residue-free antibacterial drugs to replace antibiotics.Plant essential oils,have long been considered safe and have been confirmed by studies to have broad-spectrum bacteriostatic activity.In our study,pathogenic bacteria were isolated from the diseased lung tissue of goats,recognized by staining microscopy,biochemical test,16s r RNA sequencing,and their drug resistance and pathogenicity were studied by drug susceptibility test and mouse pathogenicity test.The in vitro antibacterial activity of cinnamaldehyde against P.multocida and P.aeruginosa was studied by determination of minimum inhibitory concentration and minimum bactericidal concentration,time sterilization curve,biofilm formation.A mouse pneumonia model was established using P.multocida and P.aeruginosa,and treatment with cinnamaldehyde was used to evaluate the antibacterial efficacy in vivo.The results are as follows:1.P.multocida and P.aeruginosa were isolated,and both strains were multidrug-resistant and pathogenic.2.In vitro antibacterial activity determination,the minimum inhibitory concentration(MIC)of cinnamaldehyde against P.multocida was 0.125μL/m L,the minimum bactericidal concentration(MBC)was 0.25μL/m L,and the MIC of P.aeruginosa was 4μL/m L,and the MBC and MIC values were the same.The killing kinetics of cinnamaldehyde against P.multocida and P.aeruginosa showed a dose-dependent effect,and the faster the killing speed increased with the increase of the concentration of cinnamaldehyde drugs.On the effect of biofilm formation,cinnamaldehyde had no obvious inhibitory effect on the formation of biofilm of P.multocida.At sub-inhibitory concentrations,the formation of P.aeruginosa biofilm was inhibited at 1/2MIC and 1/4MIC,which was statistically significant.3.A pneumonia model was established with nasal induction of 30μL(10~7CFU/m L)of P.multocida,and the weight of mice in the model group was reduced,and peripheral blood leukocytes,neutrophils,alanine aminotransferase,interleukin-1β(IL-1β),interleukin-6(IL-6),tumor necrosis factor-α(TNF-α)were significantly increased.Lung tissue sections showed that the alveolar septum was significantly widened and telangiectasia was congested,hemorrhage and erythrocyte infiltration were seen in the alveolar space,and fibrinous exudation in the alveolar cavity was seen;After treatment with cinnamaldehyde,the number of white blood cells,alanine aminotransferase,IL-1β,IL-6,TNF-αin the peripheral serum of mice can be reduced,and lung lesions are significantly improved,and inflammatory cells and erythrocyte infiltration in the alveolar cavity are less,which proves to reduce the inflammatory response of mouse lung tissue.4.P.aeruginosa 30μL(10~7CFU/m L)nasal drops were used to induce the establishment of pneumonia model,and the body weight of mice in the model group decreased,and peripheral blood leukocytes,neutrophils,alanine aminotransferase,aspartate aminotransferase and IL-1β,IL-6,TNF-αwere significantly increased;Lung tissue sections showed that the lung tissue structure was disordered,the alveolar sac and alveolar structure were not obvious in some areas,and there was a large number of red blood cell infiltration in the alveolar cavity accompanied by fibrinous exudation;After treatment with cinnamaldehyde,the number of white blood cells,alanine aminotransferase,aspartate aminotransferase,IL-1β,IL-6,TNF-αin the peripheral serum of mice can be reduced,and lung lesions are significantly improved,alveolar septum is thinned,and inflammatory cells and red blood cell infiltration in the alveolar cavity are reduced.This study suggested that cinnamaldehyde has a strong bacteriostatic effect on P.multocida and P.aeruginosa,and can be used to treat pneumonia caused by P.multocida and P.aeruginosa,which provides a theoretical basis for clinical application.