Inhibitory effects of rosemary (Rosemarinus officinalis L.) essential oil on pathogenicity of irradiated and non-irradiated Pseudomonas aeruginosa

• Antipseudomonal efficacy of rosemary against irradiated clinical isolates was tested.
• Highly reduction in biofilm, cell-surface hydrophobicity and pyocyanin production
• Rosemary altered twitching, swarming and swimming ability of the irradiated isolates.
• The ultra structure resulting in ruptures of the cells and consequently cell death
• Total protein analysis indicated some changes in protein profile after treatment.

Pseudomonas aeruginosa is considered one of the most important opportunistic pathogens, which is responsible for nosocomial infections. The complex pathophysiology of infections associated with P. aeruginosa is due to its ability to grow in a biofilm mass and to produce a large number of virulence factors. This study aimed to investigate the antipseudomonal efficacy of rosemary essential oil (REO) against 25 clinical isolates control and gamma irradiated (at 24.4 Gy). Susceptibility testing towards 15 standard antibiotics and REO was carried out using disc diffusion method. The potency of REO on motility, biofilm and pyocyanin production was evaluated. Total protein profile was estimated by SDS polyacrylamide gel electroporesis. REO has showed a broad spectrum of antimicrobial activity compared to the standard antibiotics. According to their high sensitivity to REO, six isolates were chosen for MIC90 with minimum inhibitory concentration (MIC90) values ranged from 5 to 25 μl/ml. REO exerted marked effects on irradiated and non-irradiated tested isolates. The results displayed high significant reduction in biofilm and pyocyanin production. Significant reduction in cell-surface hydrophobicity was observed for some isolates. As for motility, REO altered twitching, swarming and swimming ability of the tested isolates. The ultra structure of bacterial cell results in ruptures of the bacterial cell, leakage of the cytoplasmic components and consequently cell death. Total protein analysis of control, irradiated and irradiated with treatment of REO revealed some changes in protein profile as a result of treatment. Conclusion: This study may hasten the application of REO in the treatment and prevention of pseudomonas resistant isolates in nosocomial infections.