Mechanisms for Rapid Evolution of Carbapenem Resistance in a Clinical Isolate of Pseudomonas aeruginosa .

Infections byPseudomonas aeruginosaare difficult to cure due to its high intrinsic and acquired antibiotic resistance. Once colonized the human host, and thanks to antibiotic treatment pressure,P. aeruginosausually acquires genetic mutations which provide bacteria with antibiotic resistance as well as ability to better adapt to the host environment. Deciphering the evolutionary traits may provide important insights into the development of effective combinatory antibiotic therapy to treatP. aeruginosainfections. In this study, we investigated the molecular mechanisms by which a clinical isolate (ISP50) yields a carbapenem-resistant derivative (IRP41). RNAseq and genomic DNA reference mapping were conducted to compare the transcriptional profiles andin vivoevolutionary trajectories between the two isolates. Our results demonstrated thatoprDmutation together withampChyper-expression contributed to the increased resistance to carbapenem in the isolate IRP41. Furthermore, aldcA(PA5198) gene, encoding murein tetrapeptide carboxypeptidase, has been demonstrated for the first time to negatively influence theampCexpression inP. aeruginosa.