Background
Biofilm formation by P. aeruginosa is known to be characteristic of this organism. P. aeruginosa is considered one of the most life-threatening bacteria and has been identified as a priority pathogen for research by WHO. Biofilm-producing P. aeruginosa is a concern in many parts of the world due to antibiotic resistance. Alginate also plays an important role in biofilm formation in P. aeruginosa as well as in the emergence of antibiotic resistance in biofilms. In addition, TA systems play an important role in biofilm formation. Metal NPs such as ZnO also have extensive biological properties, especially anti-biofilm properties. Therefore, this study was conducted in relation to the importance of ZnO NPs in biofilm formation and also the correlation of gene expression of TA systems in clinical isolates of P. aeruginosa.
Methods
A total of 52 P. aeruginosa isolates were collected from burns (n = 15), UTI (n = 31), and trachea (n = 6) in hospitals in Ilam between May 2020 and October 2020. Biofilm formation was assessed using a microtiter plate assay. MIC and sub-MIC concentrations of ZnO NPs (10–30 nm with purity greater than 99.8%) in P. aeruginosa were determined. Subsequently, biofilm formation was investigated using sub-MIC concentrations of ZnO NPs. Finally, total RNA was extracted and RT- qPCR was used to determine the expression levels of genes of mazEF, mqsRA, and higBA of TA systems.
Results
Six isolates of P. aeruginosa were found to form strong biofilms. The results showed that ZnO NPs were able to inhibit biofilm formation. In our experiments, we found that sub-MIC concentration of ZnO NPs increased the gene expression of antitoxins mazE and mqsA and toxin higB of TA systems treated with ZnO NPs.
Conclusions
In the present study, ZnO NPs were shown to effectively inhibit biofilm formation in P. aeruginosa. Our results support the relationship between TA systems and ZnO NPs in biofilm formation in P. aeruginosa. Importantly, the expression of antitoxins mazE and mqsA was high after treatment with ZnO NPs, but not that of antitoxin higA.