Molecular identification of toxin-antitoxin system genes and their relationship with biofilm formation among clinical isolates of Escherichia coli obtained from hospitalized and outpatients in educational hospitals in Ahvaz, Iran

Background: Toxin-antitoxin (TA) systems are present on the chromosomes and plasmids of many bacteria, including Escherichia coli. The functions of TA systems in bacteria are unclear. The biological roles of TA systems are hypothesized to include growth regulation, persistence, and biofilm development. E. coli biofilms are the source of both urinary tract infections and bacteremia. Objectives: The current investigation aims to discover the relationship between biofilm development and toxin-antitoxin systems in clinical isolates of E. coli. Materials and methods: A total of 100 E. coli isolates were tested for biofilm formation by microtiter plate assay and the presence of several TA systems such as MazF, RelE, hipA, ccdB, and MqsR. Results: Microtiter plates revealed that 90 E. coli isolates produced biofilms. The results revealed that 75 (75%), 80 (80%), 81 (81%), 58 (58%), and 51 (51%) of the isolates contained mazF, ccdB, relE, mqsR, and hipA TA loci, respectively. Conclusions: The findings suggested that TA genes are common in clinical isolates of E. coli strains. The results demonstrated that the TA system is related with biofilm development.