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

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

doi:10.3389/fmicb.2023.1229593

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

Front Microbiol. 2023 Oct 18:14:1229593. doi: 10.3389/fmicb.2023.1229593. eCollection 2023.

Authors

Guozhi Zhang^{1

2}, Lei Zhang^{2

3}, Yuning Sha², Qiaoying Chen¹, Naru Lin², Jingxuan Zhao², Yuan Zhang², Yongan Ji¹, Weiyan Jiang¹, Xueya Zhang¹, Qiaoling Li¹, Junwan Lu⁴, Xi Lin², Kewei Li², Hailin Zhang¹, Qiyu Bao^{1

2

4}, Jun Lu³, Yunliang Hu¹, Tingting Zhu¹

Affiliations

¹ The Second Affiliated Hospital and Yuying Children's Hospital, Wenzhou Medical University, Wenzhou, China.
² Key Laboratory of Medical Genetics of Zhejiang Province, Key Laboratory of Laboratory Medicine, Ministry of Education, School of Laboratory Medicine and Life Sciences, Wenzhou Medical University, Wenzhou, China.
³ Department of Clinical Laboratory, Quzhou People's Hospital, The Quzhou Affiliated Hospital of Wenzhou Medical University, Quzhou, China.
⁴ Medical Molecular Biology Laboratory, School of Medicine, Jinhua Polytechnic, Jinhua, China.

Abstract

Background: Aeromonas species have been identified as agents responsible for various diseases in both humans and animals. Multidrug-resistant Aeromonas 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.

Methods: The function of aac(6')-Va was verified by gene cloning and antibiotic susceptibility tests. To explore the in vivo activity of the enzyme, recombinant proteins were expressed, and enzyme kinetics were tested. To determine the molecular background and mechanism of aac(6')-Va, whole-genome sequencing and bioinformatic analysis were performed.

Results: The novel aminoglycoside N-acetyltransferase gene aac(6')-Va 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 aac(6')-Va, AAC(6')-Va also showed the highest catalytic efficiency for ribostamycin [k_cat/K_m ratio = (3.35 ± 0.17) × 10⁴ M^-1 s^-1]. Sharing the highest amino acid identity of 54.68% with AAC(6')-VaIc, the novel aminoglycoside N-acetyltransferase constituted a new branch of the AAC(6') family due to its different resistance profiles. The gene context of aac(6')-Va and its close relatives was conserved in the genomes of species of the genus Aeromonas.

Conclusion: The novel resistance gene aac(6')-Va confers resistance to several aminoglycosides, especially ribostamycin. Our finding of a novel resistance gene in clinical A. hydrophila will help us develop more effective treatments for this pathogen's infections.

Keywords: AAC(6′)-Va; Aeromonas hydrophila; aminoglycoside 6′-acetyltransferase; aminoglycoside resistance; aminoglycoside-modifying enzyme.

Grants and funding

This study was supported by the Science & Technology Project of Wenzhou City, China (Y20210100, N20210001), the Science & Technology Project of Jinhua City, China (2022-2-013, 2022-4-017), and Zhejiang Provincial Natural Science Foundation of China (LY19C060002 and LQ17H190001).