Lingyan Sun1,2, Yan Chen1,2, Xiaoting Hua1,2, Yiyi Chen1,2, Jinjing Hong3, Xueqing Wu1,2, Yan Jiang1,2, Willem van Schaik4, Tingting Qu3, Yunsong Yu1,2. 1. Department of Infectious Diseases, Sir Run Run Shaw Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang Province, China. 2. Key Laboratory of Microorganism Technology and Bioinformatics Research of Zhejiang Province, Hangzhou, Zhejiang Province, China. 3. State Key Laboratory for Diagnosis and Treatment of Infectious Disease, First Affiliated Hospital, College of Medicine, Zhejiang University, Hangzhou, Zhejiang Province, China. 4. Institute of Microbiology and Infection, University of Birmingham, Birmingham, UK.
Abstract
BACKGROUND: Vancomycin-variable enterococci (VVE) are a potential risk factor for vancomycin resistance gene dissemination and clinical treatment failure. vanM has emerged as a new prevalent resistance determinant among clinical enterococci in China. A total of 54 vancomycin-susceptible enterococci (VSE) isolates carrying incomplete vanM gene clusters were isolated in our previous study. OBJECTIVES: To determine the potential of vanM-carrying VSE to develop vancomycin resistance and investigate the mechanism of alteration of the resistance phenotype. METHODS: Fifty-four vanM-positive VSE strains were induced in vitro by culturing in increasing concentrations of vancomycin. Genetic changes between three parent VVE strains and their resistant variants were analysed using Illumina and long-read sequencing technologies, quantitative PCR and Southern blot hybridization. Changes in expression level were determined by quantitative RT-PCR. RESULTS: Twenty-five of the 54 VSE strains carrying vanM became resistant upon vancomycin exposure. A significant increase in vanM copy number was observed ranging from 5.28 to 127.64 copies per cell in induced resistant VVE strains. The vanM transposon was identified as tandem repeats with IS1216E between them, and occurred in either the plasmid or the chromosome of resistant VVE cells. In addition, an increase in vanM expression was observed after resistance conversion in VVE. CONCLUSIONS: This study identified tandem amplification of the vanM gene cluster as a new mechanism for vancomycin resistance in VVE strains, offering a competitive advantage for VVE under antibiotic pressure.
BACKGROUND:Vancomycin-variable enterococci (VVE) are a potential risk factor for vancomycin resistance gene dissemination and clinical treatment failure. vanM has emerged as a new prevalent resistance determinant among clinical enterococci in China. A total of 54 vancomycin-susceptible enterococci (VSE) isolates carrying incomplete vanM gene clusters were isolated in our previous study. OBJECTIVES: To determine the potential of vanM-carrying VSE to develop vancomycin resistance and investigate the mechanism of alteration of the resistance phenotype. METHODS: Fifty-four vanM-positive VSE strains were induced in vitro by culturing in increasing concentrations of vancomycin. Genetic changes between three parent VVE strains and their resistant variants were analysed using Illumina and long-read sequencing technologies, quantitative PCR and Southern blot hybridization. Changes in expression level were determined by quantitative RT-PCR. RESULTS: Twenty-five of the 54 VSE strains carrying vanM became resistant upon vancomycin exposure. A significant increase in vanM copy number was observed ranging from 5.28 to 127.64 copies per cell in induced resistant VVE strains. The vanM transposon was identified as tandem repeats with IS1216E between them, and occurred in either the plasmid or the chromosome of resistant VVE cells. In addition, an increase in vanM expression was observed after resistance conversion in VVE. CONCLUSIONS: This study identified tandem amplification of the vanM gene cluster as a new mechanism for vancomycin resistance in VVE strains, offering a competitive advantage for VVE under antibiotic pressure.
Authors: Mathilde Boumasmoud; Vanina Dengler Haunreiter; Tiziano A Schweizer; Lilly Meyer; Bhavya Chakrakodi; Peter W Schreiber; Kati Seidl; Denise Kühnert; Roger D Kouyos; Annelies S Zinkernagel Journal: mBio Date: 2022-03-28 Impact factor: 7.786