aac(6')-Iaq, a novel aminoglycoside acetyltransferase gene identified from an animal isolate Brucella intermedia DW0551

Naru Lin ^1,2 Wanna Xu ^3* DaWei Huang ⁴ Chaoqun Liu ^5* Junwan Lu ⁵ Mei Zhu ^6* Qiyu Bao ^2,5* Wei Pan ^4*

• ¹ Fujian Provincial Center for Disease Control and Prevention, Fuzhou, Fujian Province, China
• ² Key Laboratory of Medical Genetics of Zhejiang Province, Key Laboratory of Laboratory Medicine, Ministry of Education, China, School of Laboratory Medicine and Life Sciences, Wenzhou Medical Universit, Wenzhou, Zhejiang Province, China
• ³ Army 73rd group Military Hospital, Xiamen, Fujian Province, China
• ⁴ The People’s Hospital of Yuhuan, Yuhuan, China
• ⁵ Medical Molecular Biology Laboratory, School of Medicine, Jinhua Polytechnic, Jinhua, Zhejiang Province, China
• ⁶ Department of Clinical Laboratory, Zhejiang Hospital, Hangzhou, Jiangsu Province, China

Background: Bacterial resistance to aminoglycoside antimicrobials is becoming increasingly severe due to their use as commonly prescribed antibiotics. The discovery of new molecular mechanisms of aminoglycoside resistance is critical for the effective treatment of bacterial infections. Methods: Bacteria in goose feces were isolated by plate streaking. The identification and characterization of a novel resistance gene from the bacterial genome involved various techniques, including molecular cloning, drug susceptibility testing, protein expression and purification, and enzyme kinetic analysis. Additionally, whole-genome sequencing and phylogenetic studies were performed. Results: Brucella intermedia DW0551, isolated from goose feces, was resistant to 35 antibiotics, and the minimum inhibitory concentration (MIC) was particularly high for most aminoglycoside antibiotics. The novel aminoglycoside resistance gene aac(6')-Iaq encoded by B. intermedia DW0551 conferred resistance to netilmicin, sisomicin, amikacin, kanamycin, gentamicin, tobramycin, and ribostamycin. The amino acid sequence of AAC(6')-Iaq shared the highest identity (52.63%) with the functionally characterized aminoglycoside acetyltransferase AAC(6')-If. AAC(6')-Iaq contained all the conserved sites of the acetyltransferase family NAT_SF. The enzyme exhibited strong affinity and catalytic activity toward netilmicin and sisomicin. The mobile genetic element (MGE) was not found in the flanking regions of the aac(6')-Iaq and aac(6')-Iaq-like genes. Conclusion: In this work, a novel aminoglycoside acetyltransferase gene, designated aac(6')-Iaq, which conferred resistance to a variety of aminoglycoside antimicrobials, was identified in an animal Brucella intermedia isolate. Identification of new antibiotic resistance mechanisms in bacteria isolated from animals could aid in the treatment of animal and human infectious diseases caused by related bacterial species.