Disinfection Treatment of Heated Scallop-Shell Powder on Biofilm of <i>Escherichia coli</i> ATCC 25922 Surrogated for <i>E. coli</i> O157:H7

Abstract

The ability of heated scallop-shell powder (HSSP) to disinfect Escherichia coli ATCC 25922 biofilm was investigated. On account of its cryotolerance and cell surface characteristics, the E. coli strain is reportedly a useful surrogate for E. coli O157: H7 in surface attachment studies. In this study, an E. coli ATCC 25922 biofilm was formed on a glass plate, and immersed in a slurry of HSSP. Following treatment, the disinfection ability of the HSSP toward the biofilm was non-destructively and quantitatively measured by conductimetric assay. The disinfection efficacy increased with HSSP concentration and treatment time. HSSP treatment (10 mg/mL, pH 12.5) for 20 min completely eliminated biofilm bioactivity (approximately 10 8 CFU/cm 2 in non-treated biofilms). In contrast, treatment with NaOH solution at the same pH, and treatment with sodium hypochlorite (200 g/mL) reduced the activity by approximately one to three log 10 . Fluorescence microscopy confirmed that no viable cells remained on the plate following HSSP treatment (10 mg/mL). Although alkaline and sodium hypochlorite treatments removed cells from the biofilm, under these treatments, many viable cells remained on the plate. To elucidate the mechanism of HSSP activity against E. coli ATCC 25922, the active oxygen generated from the HSSP slurry was examined by chemiluminescence analysis. The luminescence intensity increased with increasing concentration of HSSP slurry. The results suggested that, besides being alkaline, HSSP generates active oxygen species with sporicidal activity. Thus, HSSP treatment could also be effective for controlling biofilms of the toxic strain E. coli O157: H7, implicated in food poisoning.

Heated Scallop-Shell Powder Treatment for Deactivation and Removal of <i>Listeria</i> sp. Biofilm Formed at a Low Temperature

“…Conductimetric assays detect microbial assay, the number of remaining viable cells in the HSSP-treated biofilm was estimated. In previous studies Kubo et al, 2013Nagasawa et al, 2011 , the number of viable attached cells better matched the proliferation values of biofilms in the RABIT tube than the number of viable planktonic cells. For the attached cells, the TTD shortened as the initial number of inoculated cells C B0 increased.…”

“…N a g a s a w a e t a l . , 2 0 1 1 , Staphylococcus aureus Sawai et al, 2013 and Escherichia coli Kubo et al, 2013 . HSSP treatment 10 mg/mL, pH 12.5 completely eliminated biofilm bioactivity and was at least as effective as sodium hypochlorite 200 ppm .…”

“…In previous studies Kubo et al, 2013Nagasawa et al, 2011Sawai et al, 2013 , the disinfection efficacy of HSSP on biofilm was non-destructively determined by constructing an attached cell calibration curve in the conductimetric assay. Electrical conductivity was measured by a RABIT TM Rapid Automated Bacterial Impedance Technique system Don Whitley Scientific Ltd., Shipley, UK .…”

Antimicrobial Characteristics of Heated Eggshell Powder

“…Seashells are also mainly composed of CaCO 3 and have exhibited antimicrobial activity after being heated Sawai, 2011;Kubo et al, 2013;Watanabe et al, 2014 . Recently, heated seashell powders, such as those from scallops and oysters, have been effective as disinfection and decontamination agents for food Asada et al, 2001;Bari et al, 2002;Mehmetoglu, 2011;Bodur and Mehmetoglu, 2012 .…”

Effect of CaO Treatment on Quality Characteristics and Storage of Mulberry (Morus alba L.) Fruits in Yecheon

“…CaO (heated scallop-shell powder) has also been demonstrated to have high disinfection efficacy against E. coli, S. typhimurium, S. aureus, and B. subtilis. The good disinfection efficacy of CaO (heated scallop-shell powder) against Salmonella biofilm (Nagasawa et al, 2011), S. aureus biofilm and E. coli ATCC 25922 biofilm (Kubo et al, 2013) has also been reported. With regards to storage, the efficacy of CaO treatment on the storage extension of both kimchi (Choi et al, 2006) and tofu has been shown.…”