Impact of Pipe Materials and Chlorination on Planktonic and Biofilm Cells of Listeria monocytogenes

Abstract

This work aimed to determine the influence of different chlorine doses to inactivate of Listeria monocytogenes biofilm cells collected from six types of pipe materials, which are commonly used in household at different biofilm ages. A laboratory-scale simulated distribution system, that consists of a design based on six different pipe materials which are: polyvinyl chloride (PVC), polypropylene (PP), polyethylene (PE), iron (I), copper (Cu) and rubber (R). Six samples of L. monocytogenes biofilm were collected from the previous designed system at three different biofilm ages (10, 40 and 90 days-old). The collected biofilm samples were exposed to different chlorine doses (0.2, 0.6, 1.0, 1.4, 1.8, 2.2, 2.6 and 3.0 mg/l) at 10 min, and then total bacterial counts using pour plate method was enumerated. The results showed that the log reduction of 90 days-old of 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 was 3. 96, 4.16, 4.21, 4.17, 4.32 and 4.03 CFU/cm 2 , respectively with the initial count of biofilm cells was 10 6 CFU/cm 2 . While the log reductions of L. monocytogenes planktonic cells were: 6.20 CFU/ml (complete reduction) at the same dose of chlorine dose. The present study concluded that the biofilm cells are more resistant to chlorine dose than planktonic cells. Moreover, the biofilm of 10 days-old is more sensitive than 40 days-old followed by 90 days-old that grows in different pipe materials. In addition, chlorine effectiveness depends on its concentration, the exposure time, nature of pipe materials and the age of biofilm.

The destruction of Escherichia coli adhered to pipe surfaces in a model drinking water distribution system via various antibiofilm agents

“…The densities of viable cells for respectively, Listeria monocytogenes and Salmonella Typhimurium biofilm developed on PVC, PP, and PE pipe products, were extended overtime to a steady‐state after 70 days, while the stable in rubber was achieved after 60 days for L. monocytogenes and 80 days for S . Typhimurium (Hemdan et al., 2015). Further, in the case of iron‐based material, the steady‐state of biofilm formation was reached after 60 days for L. monocytogenes (10 8 CFU/cm 2 ) and 70 days for S .…”

“…Likewise, the exposure to silver ions is considered safe for humans as far as a dose of 0.1 mg/L of soluble silver is not exceeded in drinking water (El Hotaby, Sherif, Hemdan, Khalil, & Khalil, 2017; Hemdan & Elliethy, 2016). Interestingly, a report implied that the majority of bacterial strains could not acquire resistance to Ag‏ ions, which made it necessary to find out a more efficient alternative disinfectant that does not cause toxicity to humans (Hemdan et al., 2015; Silver, 2003).…”

“…The detached E. coli biofilm cells (90‐day‐old) were exposed to different chlorine doses (1.0, 1.5, 2.0, 2.5, 3.0 and 3.5 mg/L) for 10 min. Subsequently, the residual chlorine was measured using N,N‐diethyl‐1,4‐phenylenediamine (DPD) method (Hemdan et al., 2015). Total cell count was also performed in each case using the pour plate method.…”

“…One mL of detached biofilm cell suspension was added into a sterile plate and pouring plate count agar (PCA) media. Further, 100 µl of such suspension was streaked on the surface plates containing Rapid HiColiform Agar (RHA) (HiMedia Co., India) using surface plate technique (Hemdan, Sedik, Kamel, & El-Taweel, 2015). The growth rate of the detached biofilm cells was estimated over the period from 15 to 90 days.…”