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Abstract
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