Abstract

OBJECTIVES: Chronic infections and treatment failure are concerning issues in patients with Pseudomonas aeruginosa infections. Persister cell formation in biofilm is considered a key reason for antibiotic resistance and treatment failure. Thus, in this study, the expression of TA type II system genes (relBE, Xre-COG5654, vapBC, and Xre-GNAT) in persister cells of biofilm was evaluated in the presence of ciprofloxacin and colistin antibiotics during exponential and stationary phases. METHODS: The impacts of ciprofloxacin and colistin were examined on persister cell formation of biofilm during the exponential and stationary phases of P. aeruginosa strains through colony count method at different time intervals in the presence of 5-fold MIC of ciprofloxacin and colistin. Furthermore, the expression of relBE, Xre-COG5654, vapBC, and Xre-GNAT genes in P. aeruginosa strains underwent antibiotic treatment for 3.5 hours during the exponential and stationary phases via qRT-PCR. RESULTS: Formation of persister cells was observed in the biofilms by P. aeruginosa strains in the presence of 5-fold MIC of ciprofloxacin and colistin when compared with the control group after 3.5 hours of incubation during both exponential and stationary phases. The number of persister cells of biofilm was higher in the stationary phase than in the exponential phase. According to the findings of qRT-PCR, ciprofloxacin and colistin may induce persister cells through enhancing the expression of type II TA systems during stationary and exponential phases. CONCLUSION: The result of this study indicated that ciprofloxacin and colistin have the potential to increase persister cells formation in biofilm through influencing the expression of type II TA systems.