Inhibitory effect of naringin, naringenin, and crocin on biofilm formation and lecA gene expression in Pseudomonas aeruginosa clinical isolates

Abstract

Biofilm formation by Pseudomonas aeruginosa is a considerable challenge in treating infections. We aimed to investigate the inhibitory effect of crocin, naringin, and naringenin on biofilm formation capacity and the expression of the lecA gene by this organism. One hundred unrepeated P. aeruginosa isolates were collected from hospitalized patients and were identified. The antibiotic resistance pattern of the isolates was determined using the disk agar diffusion method. The minimum inhibitory concentration (MIC) of naringin, naringenin, and crocin was determined by a micro broth dilution test. Then, the biofilm production ability of the isolates was evaluated before and after treatment with the investigated flavonoids using the microtiter plate test. Finally, the lecA gene expression of the isolates was checked before and after treatment with investigated flavonoids using the Real-time PCR method. Among 89 biofilm-producer isolates, 48 (53.93 %), 17 (19.1 %), and 24 (26.96 %) showed a strong, moderate, and weak biofilm formation ability. Biofilm-positive isolates were more resistant to all tested antibiotics. Also, among 41 multidrug-resistant (MDR) isolates, 33 (80.48 %) were strong biofilm producers (P-value = 0.01). A strong correlation was observed between the lecA gene expression and the biofilm production ability of the isolates (P-value = 0.000). The investigated flavonoids were significantly effective on biofilm production by P. aeruginosa. Among 10 strong-biofilm producers, all (100 %) showed a moderate ability to form biofilm after treatment with crocin (P-value = 0.02), and 6 (60 %) isolates had lost their ability to produce biofilm after treatment with the simultaneous use of crocin with ciprofloxacin or tobramycin (P-value = 0.000). Also, one isolate was grouped as biofilm-negative after treatment with naringin (P-value = 0.012). The crocin, naringin, and naringenin and their concurrent use of antibiotics decreased 2-8-fold of the lecA gene expression in strong biofilm-producer isolates (P-value˂0.05). Crocin, naringin, and naringenin can be used separately or simultaneously with antibiotics to inhibit biofilm and reduce the expression of virulence factors effective in biofilm production in P. aeruginosa.