Thesis (M.Sc.) - Cairo University - Faculty of Pharmacy - Department of Microbiology and Immunology

Microbial biofilms depression represents a major challenge to healthcare because their resistance to conventional antibiotics is dramatically in rise. Therefore, new therapeutic agents for biofilms treatment are urgently needed. This study aims to inhibit and eradicate Pseudomonas aeuroginosa biofilms by 7 plants extracts alone and combined with antibiotic. The results showed that 85% of total PS. aeruginosa isolates were biofilm producers and 25% of these isolates were classified as strong biofilm producers. The highest biofilm capacity and antibiotics resistance was observed with PS-1, which further identified as an isolate of PS. aeruginosa PAO1 by 16S rRNA gene sequencing. Effect of sub-minimum inhibitory concentration levels of these extracts in biofilm formation was investigated. The results showed that, pomegranate and rosemary extracts at 1/2 x MIC levels (3.13 and 6.25 mg/ml, respectively) exhibited the highest biofilm inhibitions (91.93 and 90.83%, respectively) in the present study. Both extracts inhibited biofilm formation by reducing of swimming, swarming and twitching motilities. Biofilm eradication of pomegranate and rosemary extracts alone, mixed, and combined with 5 different antibiotics against 48h-old biofilms was investigated. The results showed that pomegranate/rosemary/ceftazidime combination at MIC level (1.56/ 3.22/ 0.002 mg/ml, respectively) was the most effective combination in biofilm eradication (97.6%). The efficiency of this combination in destroying of biofilm structure and eliminating of bacterial cells had been proven by scanning electron microscope study. Therefore, present study suggests new promising combinations that could be used in PS. aeruginosa biofilm inhibition and eradication

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