Effect of surface roughness on Escherichia Coli biofilm formation and their susceptibility to benzalkonium chloride

The inherent natural tendency of bacterial to adhere and form biofilm on both biotic and abiotic surfaces and the consequential resistance to antimicrobial treatments remained a major concerned to humanity. A continuous flow system was designed to evaluate possibility of biofilm formation by Escherichia coli DH5a on the stainless steel (type 304) with different surface roughness under continuous nutrient supply. The effect of benzalkonium chloride (BKC) as antibacterial agent on the biofilms was also investigated. The result of the colony forming unit (CFU) count shows that bacterial attachment and subsequent biofilm formation on stainless steel coupons with average surface roughness of 1.5 ± 1.8 µm and 2.0 ± 0.09 µm were both significantly higher (p = 0.05) than those of the stainless steel coupon with lower surface roughness of 0.38 ± 1.5 µm. Meanwhile, 5 mg/mL BKC exert no pronounced effect on the biofilm formed on the three surfaces as compared to the 10 mg/mL and 20 mg/mL that removed about 50% of the cells from the respective surfaces, however, the overall effect of the three concentrations tested were significantly higher (p = 0.05) on the stainless steel coupon with the least average surface roughness of 0.38 ± 1.5 µm. These observations support the hypothesis that surface profile is one of the factors that influence biofilm formation on stainless steel surfaces and reinforced the wide spread observation that microorganisms living as biofilm tends to be resistance to antimicrobial treatment especially at lower concentrations of 5 mg/m