OBJECTIVETo observe the release of DNA from Pseudomonas aeruginosa (P. aeruginosa) induced by different concentrations of piperacillin/tazobactam (Piper) in vitro.

METHODSThe minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of Piper against 1244 strain (ATCC 27317) of P. aeruginosa were determined, respectively. This strain of P. aeruginosa was separately cultured with Piper in different concentrations at 37 degrees C for 4 h and 24 h. The samples of cultural supernatant were filtered and electrophoresis was conducted in 1.8% agarose with SYBR Gold stain. Then the images of the gel sheets were photographed.

RESULTSThis strain of P. aeruginosa was sensitive to Piper. The bacterial DNA was not detected in 4-h cultured P. aeruginosa either with or without Piper by this method. The bacterial DNA molecules could be detected in 24 h samples in cultures without Piper, and they were displayed in two zones of molecular weight over 2000 base pairs (bp) and lower than 100 bp. Similar results were observed when the MIC of piper (0.002, 0.004 g/L) were under the MIC measured at the 3rd time (0.008 g/L), but there was much more bacterial DNA with molecular weight lower than 100 bp. When Piper concentration was higher than its MIC, only smaller quantities of bacterial DNA in the area with molecular weight lower than 400 bp could be detected in 24-h culture samples.

CONCLUSIONA certain amount of bacterial DNA was released from P. aeruginosa under its natural growth circumstance. Different concentrations of Piper showed different effects on DNA release, in regard to its quantity and molecular weight, from P. aeruginosa cultures.