Effects of some antibiotics on biofilm resistance genes in pseudomonas aeruginosa

Pseudomonas aeruginosa is a Gram-negative, sporeless, motile, non-encapsulated, aerobic, opportunistic pathogen that can easily adapt to environmental conditions and also has the ability to form biofilms. Hospital and community-acquired P. aeruginosa isolates have multidrug resistance and biofilm-specific antibiotic resistance. This situation causes great problems in treatment. Biofilm-specific antibiotic resistance or biofilm resistance is closely related to the fact that cells growing in a biofilm are 10-1000 times more resistant to antibiotics. In this thesis, biofilm resistance, which is caused by the higher expression of various genes in the biofilm structure, in the presence of some antibiotics in P. aeruginosa was investigated. First, a disc diffusion test of ciprofloxacin, tobramycin, fosfomycin and piperacillin/tazobactam antibiotics was performed using P. aeruginosa (PAO1) strain and minimum inhibitory concentration (MIC) values were determined by microdilution test. In addition, the minimum biofilm inhibitor concentration (MBIC) values were determined by the crystal violet (CV) test. Then, the effect of antibiotics on motility was investigated by applying antibiotics at sub-MIC concentrations. Finally, colony biofilm testing was performed with sub-MIC concentration of antibiotics and their RNAs were isolated. These RNAs were converted into cDNA and expression levels of ndvB, tssC1, PA2070 and PA5033 genes were determined by using the RT-PCR technique. In addition, planktonic cultures were used to compare each group. According to our results, it was observed that antibiotics decreased the expression levels of biofilm resistance genes in the biofilm structure compared to planktonic cells except fosfomycin. In addition, biofilm resistance was observed in the antibiotic treatment groups compared to the non-antibiotic-treated biofilm structure.