Type II toxin/antitoxin system genes expression in persister cells of Klebsiella pneumoniae

Objective: Persistence is a subpopulation of bacteria that can tolerate high doses of antibiotics by undergoing a period of dormancy. This study aimed to investigate the hypothetical role of toxin/antitoxin systems in persister cell formation of Klebsiella pneumoniae ATCC 13883 by evaluating toxins of type II toxin/antitoxin systems expression. Methods: To determine the number of surviving cells, bacterial colonies were counted at 1, 3, 5, 7, and 24 h after treated with a lethal dose of kanamycin. The role of toxin/antitoxin systems in persister cell formation was then determined by toxins of type II toxin/antitoxin systems ( relE1 , relE2 , hipA , vapC , and doc ) expression levels using real-time PCR. Results: Our results showed the viability of persister cells after 5 h. The results of relative real-time PCR showed higher levels of toxin gene expression due to stress conditions, suggesting the possible role of toxin/antitoxin systems in persister cell formation and antibiotic tolerance. Conclusion: Considering the importance of persistence and the tolerance to antibiotics, further studies on persister cell formation and related genes such as the toxin/antitoxin system genes might help us to identify the precise mechanisms leading to persister cell formation.