Study On The Effect Of Combined Medication On Antibiotic Resistance Of Aeromonas Hydrophila In Aquatic Products

According to the World Health Organization,antibiotic resistance has become a hot issue in the field of global public health and food safety of this century.Aquaculture environment is an important link in the emergence and spread of drug resistance.A.hydrophila,which has a wide range of pathogenicity,is one of the most common pathogens in aquatic animals.In recent years,as an emerging human pathogen,this organism has also attracted people's wide attention.Research shows that a large number of A.hydrophila resistant strains and their resistant genes can be isolated from ready-to-eat seafood products from retail markets,supermarkets and restaurants.Due to the stagnant development of new antibiotics and the high cost of other biological alternative therapies,it is not suitable for popularization and application.Therefore,it is of great significance to seek new methods to prolong and maximize the clinical efficacy of existing antibiotics.This paper tested the drug sensitivity of 12 conventional antibiotics and 14 natural active ingredients to A.hydrophila.And we explored the key mechanism of drug interaction based on the"drug combinations-bacteria"system model to provide theoretical basis for targeted risk prevention and control of drug resistance of A.hydrophila in aquatic products.The main contents and results are as follows:?1?Study on the sensitivity of single antibacterial to A.hydrophila.Based on the MIC method,the sensitivity of single antibiotics and natural active components to A.hydrophila was evaluated.The experimental results show that there are eight conventional antibacterial drugs such as thiamphenicol,doxycycline,neomycin,enrofloxacin,oxytetracycline,florfenicol,sulfadimethoxine amikacin and five natural active ingredients,such as citral,linalool,geraniol,eugenol and thymol have a good inhibitory effect on A.hydrophila;According to the analysis of drug resistance results,the overall drug resistance of A.hydrophila is not optimistic.Not only is it resistant to multiple antibiotics,but also has a high degree of mediation.At present,the single drug used to control A.hydrophila can be preferred to florfenicol,and enrofloxacin,neomycin,and amikacin can be used as alternative drugs in aquaculture.?2?Study on the effect of combined drugs on the resistance of A.hydrophila and drug combination screening.Based on the CI,CA and IA models to predict the inhibitory effect of the binary drug combination on the standard strains of A.hydrophila,and the prediction accuracy of the joint effect evaluation,the results show that the CI model has a better fit and higher accuracy for the joint effect;Further,the CI model was used to evaluate the drug combination interaction to screen the synergistic drug combination,and the conservative evaluation of the selected synergistic drug combination was conducted for five wild strains.Among the selected drug combinations,18 pairs of drugs showed a synergistic effect in the entire effect concentration,13 combinations showed a synergistic effect at low fa levels,and gradually turned into an antagonistic effect as the dose increased;31 combinations at low fa levels Antagonistic and synergistic at high fa levels;8 pairs of drug combinations showed antagonistic effects over the entire effect concentration range.Drug interactions within species are highly conservative,and almost occur between drug combinations with the same mechanism of action.However,there are still a few interactions that show strain specificity within a specific concentration range.For example,the combination of"thymol+neomycin"at 84?g/mL?131?g/mL has a synergistic effect on Aeromonas while being antagonistic to Vibrio;the combination of"linalool+doxycycline"has a synergistic effect on Aeromonas in the range of 69?g/mL?106?g/mL while has an antagonistic effect on Vibrio.?3?Research about the efficacy of combined drugs and its impact on resistance based on the grass carp epithelial cell model.Selecting grass carp epithelial cells as an in vitro cell line,using imaging flow cytometry to dynamically monitor the damage and apoptosis of cells caused by the infection time of A.hydrophila.The results showed that A.hydrophila infected the cells with an infection ratio of 1:20,and the key control point of cell damage was 2?3 h;Combined with the HCS to capture the changes and differences in the early toxicity indicators ROS,MMP and Ca²⁺levels,verify that the three typical drug combinations include"neomycin+thiamphenicol","doxycycline+oxytetracycline","thymol+neomycin".The experimental results showed that the selected synergistic drug combination also showed a significant synergistic effect in sensitive cell lines in vitro,while enhancing the bactericidal efficacy,reducing the use of conventional antibiotics and their residue in the aquatic environment.