The Expression of Type II TA System Genes Following Persister Cell Formation in Pseudomonas Aeruginosa Isolates in The Exponential and Stationary Phases

Abstract

Objectives: Failure of infection therapy in the presence of antibiotics has become a major problem which has been mostly attributed to the ability of bacterial persister cell formation. Bacteria use various mechanisms to form persister cells in different phases, among which is the toxin-antitoxin (TA) systems. This study aimed at investigating the expression of type II TA system genes under the stress of ciprofloxacin and colistin antibiotics in the exponential and stationary phases.Methods: To determine the effects of ciprofloxacin and colistin on persister cell formation in the exponential and stationary phases of Pseudomonas aeruginosa strains, colony counting was performed at different time intervals in the presence of 5-fold MIC of ciprofloxacin and colistin. In addition, the expression of relBE, Xre-COG5654, vapBC, and Xre-GNAT genes in P. aeruginosa isolates was assessed 3.5 h after antibiotic treatment in the exponential and stationary phases using qRT-PCR.Results: Our results indicated the presence of persister phenotype of P. aeruginosa strains in the presence of 5-fold MIC of ciprofloxacin and colistin compared to the control after 3.5 h of incubation in the exponential and stationary phases. Also, the number of persister cells in the stationary phase was higher than that of the exponential phase. According to the results of qRT-PCR, ciprofloxacin and colistin may induce persister cells by increasing the expression of type II TA systems in stationary and exponential phases.Conclusion: Ciprofloxacin and colistin may increase the formation of persister cells by affecting the expression of type II TA systems.

Comparative analysis of five type II TA systems identified in Pseudomonas aeruginosa reveals their contributions to persistence and intracellular survival

“…According to the TADB 2.0 database, five pairs of type II TA cassettes have been identified in the P. aeruginosa PAO1 genome: PA0124/PA0123 (denoted as ParDE, par operon in the RK2 plasmid), PA4674.1/PA4674 (denoted as HigBA, host inhibition of growth), PA1030/PA1029, PA1878/PA1879, and PA3270/PA3269 (Xie et al, 2018). The increase in their expression levels were associated with ciprofloxacin-and colistin-induced persister cell formation by P. aeruginosa isolates (Golmoradi Zadeh et al, 2022). The toxin ParE protects P. aeruginosa against the quinolone and other antibiotics by inhibiting gyrase-mediated DNA supercoiling, while higher ParE concentrations are also themselves toxic to cells (Muthuramalingam et al, 2019).…”