الفهرس 
A study on the potential in vitro activity of natural products on biofilm formation by clinical and environmental isolates of pseudomonas spp
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Abstract
Multidrug-resistant opportunistic pathogen Pseudomonas aeruginosa produces surface-associated communities called biofilm, which protect pathogens by forming a complex permeability barrier for antibiotics. Biofilm formation contributes to persistence and chronic infection caused by Pseudomonas aeruginosa. In this study, we investigated the potential activity of Camellia sinensis (green tea), Olea europaea (olive), Styrax benzoin, Ocimum basilicum, Humulus lupulus, Ruta graveolans, and propolis extracts on biofilm formation, pyocyanin production and twitching motility of P. aeruginosa isolates. Moreover, the effect of green tea and olive leaf extracts were investigated on the transcription of some biofilm related genes. A total of 204 isolates of Pseudomonas spp. collected from Egyptian hospitals. Susceptibility test of the recovered isolates was done using disc diffusion method. The capability of biofilm formation by isolates was evaluated by the Congo red and 96 well polystyrene Microtiter plate methods. The minimum inhibitory concentration (MIC) of these herbal extracts investigated using the broth microdilution method. Sub-MIC of herbal extracts mixed with strong biofilm former-MDR Pseudomonas isolates to determine the percentage of biofilm inhibition. The expression of lasI, lasR, rhlI and rhlR genes in isolated strains was detected using real-time rt-PCR. Susceptibility test revealing that about 49% of the isolates were multidrug-resistant.More than 90% of the isolates were biofilmforming, 26% were strong biofilm producers, 39% were moderate biofilm producers, 25% were weak biofilm producers and 10% couldn{u2019}t form any detectable biofilm. Sub-inhibitory concentrations of plant extracts mixed with strong biofilm former- MDR Pseudomonas isolates to determine the percentage of biofilm inhibition