| Microbes related to abalone diseases are mostly bacteria such as vibrio species,which are the predominant opportunistic bacterial pathogens in marine environments.Currently it is reported abalone-related pathogens which include Vibrio alginolytic,Vibrio parahaemolyticus,Vibrio fluvialis,Vibrio splendidus,Vibrio harveyi,etc.Antibiotics have been used in attempts to control bacterial diseases in aquaculture so far.Because of the misuse and abuse of antimicrobials,the pathogen of aquaculture water is under stress resulting in producing of resistant isolates and even multi-drug resistance.Eventually,it led to antibiotic treatments ineffective causing vicious cycle.The research on antibiotic resistance mainly focused on fish and shrimp in aquaculture.However,there were few studies on the drug resistance and resistance mechanisms of shellfish.Therefore,in the article,the resistance of heterotrophic bacteria collected from the abalone intestines and aquaculture environment of four farms were investigated.Enrofloxacin-sensitive Vibrio harveyi was selected from the obtained heterotrophic bacteria of the abalone intestines and was performed resistance induction.The HL-R and HL-S were conducted transcriptome analyses to study the mechanism of Vibrio harveyi resistance in shellfish from the molecular level.The results of this study would serve as theoretical basis for the prevention and treatment of bacterial diseases in aquaculture.575 heterotrophic bacteria isolates from intestines of abalone(266 strains)and rearing seawater(309 strains)and were tested to ten antibiotics using kirby–bauer diffusion method.Resistant rates of strains to penicillin G,kanamycin,gentamicin and rifampicin were high(abalone-derived heterotrophic bacteria were 40%~80.65%,isolates from seawater were 27.03%~83.95%),the proportion of bacteria resistant to norfloxacin,chloramphenicol and enrofloxacin was rather low(abalone-derived heterotrophic bacteria were 0~16.13%,isolates from seawater were 0~6.94%).Treated with a sub-inhibitory concentration of enrofloxacin after 20 serial passages,the minimal inhibitory concentration of enrofloxacin had increased by 32-fold(16?g/m L,initial strain was 0.5 ?g/m L),and once stable resistance to drugs is acquired which persists even if the stress of drugs had been removed.A total of 3522 differentially expressed genes were identified by transcriptome analysis of Vibrio harveyi resistant strains and susceptible strains,among which 2620 genes were up-regulated,902 were down-regulated.10 drug-resistant genes differentially expressed genes,respectively for gyr A?gyrB,recA,lexA,acr A,acrB,tolC,marR,gene699 and luxR were confirmed by quantitative real-time PCR.It was showed that the results were consistent with transcriptome data,indicating the reliability of transcriptome data.Difference genes between these two samples were used for GO analysis and then functionally annotated the unigenes with gene descriptions.We obtained 31 GO functional category annotations,based on these annotations,the dominant terms between resistant and susceptible strains were "metabolic process","cell composition","catalytic activity" and "binding".There existed two major findings at the gene level when Vibrio harvey was induced into enrofloxacin-resistant strains by transcriptome analysis: 1.The expression of genes related to active efflux pump system(RND,MATE,MFS,ABC)was up-regulated as well as Vibrio harvey;2.The expression of recA gene regulating soar start and other SOSr related genes was increasing,while the expression of Lex A was the opposite.The bacteria actives SOSr in vivo.The discovery above laid the data reference of molecular for in-depth study of Vibrio harvey resistance to quinolones drug molecular mechanism. |
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