Comparative transcriptomic analysis reveals the molecular mechanisms related to oxytetracycline- resistance in strains of Aeromonas hydrophila

Abstract Antibiotic resistance among aquatic bacterial pathogens has become a serious concern in aquaculture environments, which has increased research interest to develop solutions to overcome this problem. Moreover, the activities of several Aeromonas hydrophila gene pathways have remained elusive concerning antibiotic resistance evolution. Therefore, in this study, we have performed a transcriptomic analysis to compare differentially expressed genes between oxytetracycline (OXY) susceptible and resistant strains of A. hydrophila. Compared to the A. hydrophila susceptible strain, a total of 22 and 185 genes were differentially expressed in the 4-fold minimal inhibitory concentration (MIC) and 8-fold MIC resistant strains, respectively. Furthermore, the bioinformatics analysis revealed that the sulfur metabolism-related genes were down-regulated. The genes responsible for mannitol metabolism and the efflux pump system were up-regulated in resistant strains, compared to the susceptible strain. Therefore, it suggests that these three pathways may be involved in the OXY resistance evolution in A. hydrophila. The outcome of the transcriptomic data was further validated through quantitative reverse transcription-PCR (qRT-PCR) and Western blot analysis. Overall, the obtained data provides a deeper insight into the intrinsic molecular mechanism of OXY resistance evolution in A. hydrophila.