Effect of Subinhibitory concentrations of imipenem and piperacillin on transcriptional expression of algD and lasB genes in Pseudomonas aeruginosa

Sub Minimal Inhibitory concentrations (sub-MIC) of antibiotics, although not able to kill bacteria, can be effect on their physico- chemical characteristics and functions. This study aimed to investigate the effect of sub-MIC of imipenem and piperacillin on the transcriptional expression of virulence related genes algD and lasB in Pseudomonas auroginosa. Five clinical isolates of P. aeruginosa were screened for the presence of algD and lasB genes and minimum inhibitory concentration (MIC) of imipenem and piperacillin was determined using tube dilution method. The expression level of algD and lasB at sub-MIC concentrations of antibiotics was measured by real-time PCR. Our results showed that the expression of the lasB strongly decreased at all sub-MIC of piperacillin, especially at concentrations 0.125 and 2 µg/ml (P< 0.05). Whereas, a slight increase of the algD expression was measured at concentrations 16, 4, 2, 1, 0.25 and 0.125 µg/ml of piperacillin. At subMIC of imipenem, the algD expression was decreased 0.3 to 1.6 fold and the expression of lasB was decreased at concentrations of 0.25, 2, 4 and 8 µg/ml. However, imipenem had no significant influence on algD and lasB expression. Further studies will be required in order to assess whether sub-MIC of piperacillin can be improve the outcomes of severe and serious infections caused by P. aeruginosa.