Inactivation of Bacillus anthracis Spores by a Combination of Biocides and Heating under High-Temperature Short-Time Pasteurization Conditions

Abstract

The milk supply is considered a primary route for a bioterrorism attack with Bacillus anthracis spores because typical high-temperature short-time (HTST) pasteurization conditions cannot inactivate spores. In the event of intentional contamination, an effective method to inactivate the spores in milk under HTST processing conditions is needed. This study was undertaken to identify combinations and concentrations of biocides that can inactivate B. anthracis spores at temperatures in the HTST range in less than 1 min. Hydrogen peroxide (HP), sodium hypochlorite (SH), and peroxyacetic acid (PA) were evaluated for their efficacy in inactivating spores of strains 7702, ANR-1, and 9131 in milk at 72, 80, and 85°C using a sealed capillary tube technique. Strains ANR-1 and 9131 were more resistant to all of the biocide treatments than strain 7702. Addition of 1,260 ppm SH to milk reduced the number of viable spores of each strain by 6 log CFU/ml in less than 90 and 60 s at 72 and 80°C, respectively. After neutralization, 1,260 ppm SH reduced the time necessary to inactivate 6 log CFU/ml (TTI6-log) at 80°C to less than 20 s. Treatment of milk with 7,000 ppm HP resulted in a similar level of inactivation in 60 s. Combined treatment with 1,260 ppm SH and 1,800 ppm HP inactivated spores of all strains in less than 20 s at 80°C. Mixing 15 ppm PA with milk containing 1,260 ppm SH resulted in TTI6-log of 25 and 12 s at 72 and 80°C, respectively. TTI6-log of less than 20 s were also achieved at 80°C by using two combinations of biocides: 250 ppm SH, 700 ppm HP, and 150 ppm PA; and 420 ppm SH (pH 7), 1,100 ppm HP, and 15 ppm PA. These results indicated that different combinations of biocides could consistently result in 6-log reductions in the number of B. anthracis spores in less than 1 min at temperatures in the HTST range. This information could be useful for developing more effective thermal treatment strategies which could be used in HTST milk plants to process contaminated milk for disposal and decontamination, as well as for potential protective measures.The bioterrorist attack with Bacillus anthracis spores in 2001 in the United States stressed the need for strengthening the biodefense system, especially for the food supply. Bacillus anthracis is one of the potential bioterrorism agents which could be deliberately released into the milk production, processing, and distribution system. This concern has fueled interest in studying new methods for inactivation of B. anthracis spores in milk. Since pasteurization is a standard process in milk plants, it could be adapted to develop a thermal process capable of inactivating B. anthracis spores. Such a process could be easily adopted by high-temperature short-time (HTST) milk pasteurizers in the event of a bioterrorist attack for decontamination and disposal.A series of thermal inactivation kinetic parameters at 72 to 103°C were determined in our previous study (24). The results of that study confirmed that standard HTST pasteurization processes (e.g., 72°C for 15 s) had little...

Inactivation of Neosartorya fischeri and Paecilomyces variotii on paperboard packaging material by hydrogen peroxide and heat

“…Hydrogen peroxide is known to be effective against a wide range of microorganisms (Hilgren, Swanson, Diez-Gonzalez, & Cords, 2009;Lin, Moon, Doyle, & McWatters, 2002;Podolak, Elliott, Taylor, Khurana, & Black, 2009;Venkitanarayanan, Zhao, & Doyle, 1999;Xu, Labuza, & Diez-Gonzalez, 2008). Some studies report on the inactivation of bacterial spores by hydrogen peroxide (Hilgren et al, 2009;Podolak et al, 2009;Xu et al, 2008), however, to the authors' best knowledge there is no research that regards the inactivation of heat resistant molds that may contaminate paperboard materials used in the aseptic processing.…”

“…Some studies report on the inactivation of bacterial spores by hydrogen peroxide (Hilgren et al, 2009;Podolak et al, 2009;Xu et al, 2008), however, to the authors' best knowledge there is no research that regards the inactivation of heat resistant molds that may contaminate paperboard materials used in the aseptic processing. Heat-resistant molds such as Byssochlamys, Neosartorya, Talaromyces, Eupenicillium and anamorph with asexual spores such as Paecilomyces are well-known because of their high heat and chemical resistances (Salomão, Massaguer, & Aragão, 2008;Sant'Ana, Rosenthal, & Massaguer, 2009;Tournas, 1994;Tribst, Franchi, Cristianini, & Massaguer, 2009), involvement in food spoilage (Beuchat & Pitt, 2001;Tribst et al, 2009) and ability to produce mycotoxins (Beuchat & Pitt, 2001;Sant'Ana et al, 2010).…”

Principles and Practice of Disinfection of Biological Warfare Agents – How Clean is Clean Enough?

“…For example, Xu et al inactivated Bacillus anthracis spores effectively in milk by a combination of heat and hydrogen peroxide [21], while Urakami and coworkers successfully combined ozone treatment with UV irradiation [22]. In addition, joint effects of heat and hydrostatic pressure for complete destruction of Bacillus species spores were observed.…”

Size reduction of Aspergillus versicolor fungal bioaerosols during a thermal heating process in continuous-flow system

“…Among them, the antimicrobial treatment of indoor air using a thermal heating process is considered safe, effective, and environment-friendly; it does not produce secondary byproducts such as ozone or ions. Some studies on heat treatment have targeted airborne bacterial spores, which are widely used as surrogates for biological warfare agents (Decker, Citek, Harstad, Gross, & Piper, 1954;Grant, Hitchings, McCartney, Ferguson, & Rowe, 2002;Mullican, Buchanan, & Hoffman, 1971;Xu, Labuza, & Diez-Gonzalez, 2008), whereas others have focused on environmental parameters for the culture and survival of vegetative cells (Ehrlich, Miller, & Walker, 1970;Fine & Gervais, 2005;Theunissen, Toom, Burggraaf, Stoiz, & Michel, 1993). Our recent studies showed that a high-temperature, short-time (HTST) process, a type of thermal heating process, can effectively inactivate fungal and bacterial bioaerosols in a continuous-flow system (Jung, Lee, & Kim, 2009a;.…”