Porin deficiency or plasmid copy number increase mediated carbapenem-resistant resistance evolution.
Guoxiu Xiang, Zhiwei Zhao, Shebin Zhang, Yimei Cai, Yuting He, Jianming Zeng, Cha Chen, Bin Huang
Author Information
Guoxiu Xiang: Department of Laboratory Medicine, The First Affiliated Hospital of Sun Yat-sen University, Guangzhou, People's Republic of China.
Zhiwei Zhao: Department of Laboratory Medicine, The First Affiliated Hospital of Sun Yat-sen University, Guangzhou, People's Republic of China.
Shebin Zhang: Department of Laboratory Medicine, Guangdong Provincial Hospital of Traditional Chinese Medicine, Guangzhou, People's Republic of China.
Yimei Cai: Department of Laboratory Medicine, Guangdong Provincial Hospital of Traditional Chinese Medicine, Guangzhou, People's Republic of China.
Yuting He: Department of Laboratory Medicine, The First Affiliated Hospital of Sun Yat-sen University, Guangzhou, People's Republic of China.
Jianming Zeng: Department of Laboratory Medicine, Guangdong Provincial Hospital of Traditional Chinese Medicine, Guangzhou, People's Republic of China.
Cha Chen: Department of Laboratory Medicine, Guangdong Provincial Hospital of Traditional Chinese Medicine, Guangzhou, People's Republic of China.
Bin Huang: Department of Laboratory Medicine, The First Affiliated Hospital of Sun Yat-sen University, Guangzhou, People's Republic of China.
This study investigated resistance evolution mechanisms of conjugated plasmids and bacterial hosts under different concentrations of antibiotic pressure. Ancestral strain ECNX52 was constructed by introducing the -carrying IncX3 plasmid into C600, and was subjected to laboratory evolution under different concentrations of meropenem pressure. Minimal inhibitory concentrations and conjugation frequency were determined. Fitness of these strains was assessed. Whole genome sequencing and transcriptional changes were performed. Ancestral host or plasmids were recombined with evolved hosts or plasmids to verify plasmid or host factors in resistance evolution. Role of the mutation on plasmid copy number was determined. Two out of the four clones (EM2N1 and EM2N3) exhibited four-fold increase in MIC when exposed to a continuous pressure of 2 μg/mL MEM (1/32 MIC), by down regulating expression of outer membrane protein . Besides, all four clones displayed four-fold increase in MIC and higher conjugation frequency when subjected to a continuous pressure of 4 μg/mL MEM (1/16 MIC), attributing to increasing plasmid copy number generated by D140Y (GAT→TAT) mutation. Bacterial hosts and conjugative plasmids can undergo resistance evolution under certain concentrations of antimicrobial pressure by reducing the expression of outer membrane proteins or increasing plasmid copy numbers.
