Quantitative proteomics reveals the molecular mechanism of Aeromonas hydrophila in enoxacin stress.

Aeromonas hydrophila is an aquatic pathogen that has been of increasing concern in cultivation fisheries because of antibiotics resistance; however, its intrinsic antibiotics resistance mechanism remains elusive. In this study, a label-free-based proteomics method was used to compare differential protein abundances in response to enoxacin (ENX) stress in A. hydrophila. The results showed a total of 96 proteins were altered, with 43 increased and 53 decreased. Subsequent bioinformatics analysis showed that 11 SOS response-related proteins increased and four chemotaxis proteins decreased in response to ENX stress. Further antibiotics susceptibility assay showed that SOS response inhibitors such as baicalein and curcumin significantly enhanced the bactericidal capacity when compounded with ENX but not with chlortetracycline. These findings indicate the importance of SOS response in quinolones resistance. Moreover, the survival rates of five related knock-out strains (ΔuvrA, ΔahyR, ΔompW, ΔcheV, and ΔhgpB) were compared in response to different doses of ENX. Finally, the auto-inducer 1 (AI-1) quorum sensing system may negatively regulate ENX resistance in A. hydrophila. Overall, our data provide insight into the quinolones resistance mechanism and indicate that an effective SOS response inhibitor compound with ENX may be a promising strategy for the treatment of quinolones-resistant A. hydrophila. BIOLOGICAL SIGNIFICANCE: Bacterial antibiotics resistance has become a very serious public health problem, whereas its intrinsic mechanism remains elusive. To investigate the antibiotics resistant characteristics of fish pathogenic Aeromonas hydrophila, we compared the differential protein abundances in response to enoxacin (ENX) stress using proteomics method in this study. Our bioinformatics analysis showed that SOS response-related proteins increased and chemotaxis proteins decreased in response to ENX stress. Further assays showed that SOS response inhibitors such as baicalein and curcumin significantly enhanced the bactericidal capacity when compounded with ENX but not with chlortetracycline. Moreover, the antibiotics susceptibility of five related knock-out strains were valued in different doses of ENX. Overall, our data provide insight into the quinolones resistance mechanism and indicate that SOS response process and quorum sensing may involve in ENX resistance in A. hydrophila.