Evaluation of Resistance Mechanisms to Meropenem in Pseudomonas aeruginosa Isolates

In vitro efficacy of meropenem was investigated in 102 Pseudomonas aeruginosa isolates, which were isolated from patients in the intensive care unit of our hospital, using macrodilution method. Nine P. aeruginosa isolates were found to be resistant to meropenem. Plasmids were isolated by alkali lysis miniprep method. Plasmids identified were > 100, 90, 35, 28, 4.5, 4.3, 4, 2.3, 2, 1, 0.7 kb in size. Common and replicative plasmids were purified and whether they transmitted meropenem resistance or not, was investigated by transformation and conjugation methods. It was not possible to transfer meropenem resistance to recipient bacteria. Therefore, we presumed that meropenem resistance was either chromosomal or by way of chromosomally integrated transposons.