Efficiency of Sodium Hypochlorite Sanitizer against Listeria Monocytogenes and Staphylococcus Aureus Biofilms Grown in Watermelon Flesh Extract

Ng, Timothy Jian Wen (2020) Efficiency of Sodium Hypochlorite Sanitizer against Listeria Monocytogenes and Staphylococcus Aureus Biofilms Grown in Watermelon Flesh Extract. Final Year Project (Bachelor), Tunku Abdul Rahman University College.

Text Timothy Ng Jian Wen_Full Text.pdf Restricted to Registered users only Download (654kB)

Abstract

Listeria monocytogenes and Staphyloccocus aureus are both Gram-positive pathogens that are the cause of foodborne illness outbreaks in various food processing environments. Outbreaks happen due to the contamination of food with the pathogens, which are then ingested. One of the objectives of this study was to compare the biofilm forming abilities of L. monocytogenes single-species biofilm, S. aureus mono-species biofilm and a dual-species biofilm variant of these two pathogens when grown in watermelon flesh extract. The food contact surfaces used in this study were polypropylene coupons with dimensions of 1 cm × 2 cm × 0.2 cm each. Overall, all three biofilm variants showed a similar biofilm forming ability and there was an increase in biofilm when they were incubated at 25oC for 1, 2, 4, 6, 8, 24, 48, 120, 168, 240 hours. However, the dual-species biofilm showed a slight decrease in cells during the exponential growth phase. The results showed that within the dual-species biofilm, L. monocytogenes was the dominant species as the plate count results showed more L. monocytogenes colonies compared to S. aureus colonies. The other objective of this study was to compare the efficiency of commonly used sanitizer sodium hypochlorite in removing adhering biofilm communities on the three biofilm variants through enumeration of surviving viable cells. The sanitization treatment was carried out on 120-hour and 240-hour old biofilms using commercially bought sodium hypochlorite solution with 150 ppm concentration. The log reduction in log cfu/cm2 for L. monocytogenes single-species, S. aureus single-species, and dual-species biofilms were 1.86, 0.90, 0.49 for 5 days and 1.70, 0.97, 1.10 for 10 days respectively. Only 5-day old L. monocytogenes single-species biofilm had a significant difference (p < 0.05). The others had no significant difference within their own groupings (p > 0.05).