The effects of Tomatidine alkaloid on biofilm formation and the exprsssion of quorum sensing associated genes in Pseudomonas aeruginosa

Quorum sensing system plays an important role in regulating pathogenic propertise and biofilm formation of Pseudomonas aeruginosa. Therefore, inhibiting the quorum sensing system can be a suitable solution in the treatment of infections related to Pseudomonas aeruginosa biofilm. This study was conducted to investigate the effects of sub-inhibitory concentretions of tomatidine on the expression of quorum sensing genes and biofilm formation in Pseudomonas aeruginosa.

The present study was a laboratory interventional study. Biofilm formation was evaluated by microtiter plate method. The RNA of all bacteria was extracted using a column RNA isolation kit and the expression of lasI, lasR, rhlI, rhlR and algD genes in both    normal conditions and after treatment with tomatidine was analyzed. Antibiotic resistance was evaluated by the disk diffusion method.

 The highest and least antibiotic resistance was detected against ticarcillin (80%) and colistin (5%), respectively. Tomatidine up to a concentration of 2 mg/ml had no inhibitory effect on Pseudomonas aeruginosa. 55% of the strains were weak biofilm producers and 45% were strong biofilm producers. The expression of all genes and biofilm formation increased after treatment with tomatidine. The lasI and rhlR genes were respectively the most and least affected genes. Among the five genes examined, only rhlR is significantly more expressed in weak biofilm producers.

The results showed, contrary to expectation, the sub-MIC concentrations of tomatidine increase the expression of quorum sensing genes and biofilm formation in Pseudomonas aeruginosa.