Subinhibitory antibiotic concentrations promote the horizontal transfer of plasmid-borne resistance genes from Klebsiellae pneumoniae to Escherichia coli
Manlin Ding, Zi Ye, Lu Liu, Wei Wang, Qiao Chen, Feiyang Zhang, Ying Wang, Åsa Sjöling, Alberto J. Martín‐Rodríguez, Renjing Hu, Wenbi Chen, Yingshun Zhou
Abstract
Horizontal gene transfer plays an important role in the spread of antibiotic resistance, in which plasmid-mediated conjugation transfer is the most important mechanism. While sub-minimal inhibitory concentrations (sub-MIC) of antibiotics could promote conjugation frequency, the mechanism by which sub-MIC levels of antibiotics affect conjugation frequency is not clear. Here, we used Klebsiella pneumoniae SW1780 carrying the multi-drug resistance plasmid pSW1780-KPC as the donor strain, to investigate the effects of sub-MICs of meropenem (MEM), ciprofloxacin (CIP), cefotaxime (CTX), and amikacin (AK) on conjugational transfer of pSW1780-KPC from SW1780 to Escherichia coli J53. Our results showed that the transfer frequencies increased significantly by treating SW1780 strain with sub-MIC levels of MEM, CIP, CTX and AK. Transfer frequencies at sub-MIC conditions in a Galleria mellonella were significantly higher than in vitro . To investigate gene expression and metabolic effects, RT-qPCR and LC–MS-based metabolome sequencing were performed. Transcript levels of T4SS genes virB1 , virB2 , virB4 , virB8 , and conjugation-related genes traB , traK , traE , and traL were significantly upregulated by exposure to sub-MICs of MEM, CIP, CTX, and AK. Metabolome sequencing revealed nine differentially regulated metabolites. Our findings are an early warning for a wide assessment of the roles of sub-MIC levels of antibiotics in the spread of antibiotic resistance.