zahra rajabloo

Bacteria create biofilms as a mechanism to increase survival. The use of antibiotics to fight against them causes antibiotic resistance. Therefore, there is a need to produce strong anti- biofilm substances to fight biofilms. This experimental study was conducted with the aim of investigating the effects of malachite / zinc oxide / chitosan nanocomposites on the expression of pathogenic genes in Pseudomonas aeruginosa and Staphylococcus aureus.

Experimental, malachite, malachite / zinc oxide and malachite / zinc oxide / chitosan nanocomposites were prepared. The amount of biofilm formation of bacteria was checked with the help of crystal violet dye and TTC. The Minimum Biofilm Inhibitory Concentration and the Minimum Biofilm Eradication Concentration were investigated to measure the anti- biofilm activity of nanocomposites. The extent of cell survival in the vicinity of nanocomposites was evaluated by calcein-AM staining. The expression of rhlI and lasI genes in Pseudomonas aeruginosa and fnbA and fnbB genes in Staphylococcus aureus were investigated using Real- Time PCR technique. Data were analyzed using ANOVA test.

Based on the results of this study, the highest amount of anti- biofilm activity was observed in malachite / zinc oxide / chitosan, malachite / zinc oxide, and malachite nanocomposites, respectively. The results showed that the final malachite / zinc oxide / chitosan nanocomposite with a concentration of 7.81 μg/ml could inhibit the biofilm formation of two bacteria by about 50 ± 10% (MBIC50) and with a concentration of 15.62 μg/ml, the biofilm formed by both bacteria were remove about 50 ± 10% (MBEC50). Malachite / zinc oxide and malachite / zinc oxide / chitosan nanocomposites reduced the expression of rhlI and lasI genes of Pseudomonas aeruginosa and fnbA and fnbB genes of Staphylococcus aureus bacteria (P < 0.001). The use of malachite / zinc oxide / chitosan final nanocomposite reduced rhlI gene expression by 166.66 times, lasI gene expression by 30.30 times, fnbA expression by 20.70 times, and fnbB expression by 100 times compared to the control group (P < 0.001).

Malachite / zinc oxide and malachite / zinc oxide / chitosan nanocomposites probably have anti- biofilm activity on Pseudomonas aeruginosa and Staphylococcus aureus bacteria.