Biofilm establishment, biofilm persister cell formation, and relative gene expression analysis of type II toxin-antitoxin system in Klebsiella pneumoniae

The biofilms forming ability in Klebsiella pneumoniae isolates leads to treatment failure and chronic infections through protecting bacteria against antibiotics. Persister cells are a small fraction of the bacterial population that survives by entry into dormancy state after treatment with high dose antibiotics and are mainly responsible for a high level of biofilm-mediated tolerance to antibiotics. Toxin-antitoxin (TA) systems widely distributed among bacteria. Activation of the TA system is believed to result in the bacterial entrance to the dormant state, inducing persistence, and the formation of biofilms. In this study after biofilm formation and the induction of persister cells in biofilms, the relative expression level of type II TA system genes (relE1/relB1, relE2/relB2, hipA/hipB, vapB/vapC, phd/doc, mazF/mazE) in K. pneumoniae isolates were examined by Real _Time PCR. Findings showed an increase in the expression levels of type II TA system genes in biofilm formers and an upregulation of all genes studied in biofilm persister cells except the phd/doc system. Our results can provide information about the potential role of the TA systems in biofilm production and also the biofilms persister cell formation.