5018
Bahaa El-Din Ahmed Mohamed Hemdan
BIOLOGICAL CHARACTERISTICS OF SOME MICROBES CONTRIBUTING IN BIOFILM FORMATION
Biofilm, pathogenic microbes, EPS, chlorine, AgNPs, antibiotics
The aims of this study were to determine microbial population contributing in natural biofilm. In addition to, study the behavior and biological characteristics of two pathogenic bacteria including L. monocytogenes and S. Typhimurium in biofilm state. To achieve first aim, forty eight natural biofilm samples were collected from different types of microhabitats to determine the characteristics of the predominant microorganisms. The results of natural biofilm samples showed that the most frequent pathogens were Staph. aureus, L. monocytogenes, Salmonella spp and Candida albicans in all tested samples. While, to achieve second aim, water distribution system model was designed for testing of these bacteria. Six samples of synthetic biofilm were collected at three different biofilm ages (10, 40 and 90 days-old). The collected biofilm samples were exposed to different antimicrobial agents. Results cleared that the highest growth of L. monocytogenes and S. Typhimurium biofilm was reported in I pipe material. Results showed the log reduction of 90 days-old L. monocytogenes biofilm formation, when exposed to 3.0 mg/l of chlorine dose, on six pipe materials; PVC, PP, PE, I, Cu and R been 3.96, 4.16, 4.21, 4.17, 4.32 and 4.03 CFU/cm2, respectively. While, the effective MICs of Ag ions were 500 mg at 5 min against 90 days-old L. monocytogenes and 300 at 15 min for S. Typhimurium biofilm. Additionally, the effective MICs of AgNPs were recorded 500 mg at 15 min for 90 days-old L. monocytogenes and 500 mg at 10 min for S. Typhimurium. On the other hand, the results of antibiotic susceptibilityindicated the planktonic cells were more sensitive than the biofilm cells. Also, the longest survival time in tested water of L. monocytogenes and S. Typhimurium biofilm cells scraped from I pipe material was observed. In contrast, the shortest survival time of biofilm cells scraped from Cu pipe material was recorded.
2015
Ph.d
Cairo
Agriculture