AUTHOR=Zhang Guozhi , Zhang Lei , Sha Yuning , Chen Qiaoying , Lin Naru , Zhao Jingxuan , Zhang Yuan , Ji Yongan , Jiang Weiyan , Zhang Xueya , Li Qiaoling , Lu Junwan , Lin Xi , Li Kewei , Zhang Hailin , Bao Qiyu , Lu Jun , Hu Yunliang , Zhu Tingting 

TITLE=Identification and characterization of a novel 6′-N-aminoglycoside acetyltransferase AAC(6′)-Va from a clinical isolate of Aeromonas hydrophila

JOURNAL=Frontiers in Microbiology

VOLUME=14

YEAR=2023

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2023.1229593

DOI=10.3389/fmicb.2023.1229593

ISSN=1664-302X

ABSTRACT=<sec id="sec1"><title>Background</title><p><italic>Aeromonas</italic> species have been identified as agents responsible for various diseases in both humans and animals. Multidrug-resistant <italic>Aeromonas</italic> strains pose a significant public health threat due to their emergence and spread in clinical settings and the environment. The aim of this study was to determine a novel resistance mechanism against aminoglycoside antimicrobials in a clinical isolate.</p></sec><sec id="sec2"><title>Methods</title><p>The function of <italic>aac(6′)-Va</italic> was verified by gene cloning and antibiotic susceptibility tests. To explore the <italic>in vivo</italic> activity of the enzyme, recombinant proteins were expressed, and enzyme kinetics were tested. To determine the molecular background and mechanism of <italic>aac(6′)-Va</italic>, whole-genome sequencing and bioinformatic analysis were performed.</p></sec><sec id="sec3"><title>Results</title><p>The novel aminoglycoside <italic>N</italic>-acetyltransferase gene <italic>aac(6′)-Va</italic> confers resistance to several aminoglycosides. Among the antimicrobials tested, ribostamycin showed the highest increase (128-fold) in the minimum inhibitory concentration (MIC) compared with the control strains. According to the MIC results of the cloned <italic>aac(6′)-Va</italic>, AAC(6′)-Va also showed the highest catalytic efficiency for ribostamycin [<italic>k</italic><sub>cat</sub>/<italic>K</italic><sub>m</sub> ratio = (3.35 ± 0.17) × 10<sup>4</sup> M<sup>−1</sup> s<sup>−1</sup>]. Sharing the highest amino acid identity of 54.68% with AAC(6′)-VaIc, the novel aminoglycoside <italic>N</italic>-acetyltransferase constituted a new branch of the AAC(6′) family due to its different resistance profiles. The gene context of <italic>aac(6′)-Va</italic> and its close relatives was conserved in the genomes of species of the genus <italic>Aeromonas</italic>.</p></sec><sec id="sec4"><title>Conclusion</title><p>The novel resistance gene <italic>aac(6′)-Va</italic> confers resistance to several aminoglycosides, especially ribostamycin. Our finding of a novel resistance gene in clinical <italic>A. hydrophila</italic> will help us develop more effective treatments for this pathogen’s infections.</p></sec>