ARS | Publication request: The Efficiency of Conventional Pasterurization Temperatures on Bacillus Anthracis (Sterne) Spores in Water, Media, and Milk

Submitted to: International Association For Food Protection
Publication Acceptance Date: February 1, 2004
Publication Date: August 12, 2004
Citation: Novak, J.S., Call, J.E., Wallace, F.M., Tomasula, P.M., Luchansky, J.B. 2004. The Efficiency Of Conventional Pasterurization Temperatures On Bacillus Anthracis (Sterne) Spores In Water, Media, And Milk [abstract]. International Association For Food Protection Annual Meeting. P167.

Technical Abstract: Although the likelihood of natural contamination of milk with B. anthracis from infected animals is small, there is potential for purposeful addition of spores to bulk milk exceeding 1,000,000 spores/ml. High temperature-short time (HTST) pasteurization at the legal minimum time and temperature condition (72oC for 15 sec), or at higher temperatures and longer times (78oC for 30 sec), or at ultra-high temperature pasteurization (130oC for 1-2 sec) have been successful in reducing levels of vegetative cells of pathogens in milk, but may be ineffective against heat resistant spores. The decimal reduction times (D-values) for B. anthracis (Sterne) spores inoculated to 1,000,000,00 spores/ml in dH2O, brain heart infusion (BHI) broth, or skim milk (SM) were calculated at these pasteurization temperatures. Pasteurization at 72oC was ineffective (< 1log10 CFU/ml reduction) in reducing spore viability for B. anthracis (Sterne) in all 3 test fluids for treatments up to 90 min. The D values at 78 C were estimated at 115.4 + 32.3 min for spores in dH2O, 612.9 + 431.5 min for spores in BHI, and 640.3 + 513.3 min for spores in SM. As evidenced by D values at 130C of 0.7 + 0.2 min for spores in dH2O, 0.9 + 0.3 min for spores in BHI, and 1.1 + 0.1 min for spores in SM, respectively, ultra-high pasteurization conditions were also found to be inadequate for inactivating spores. In related studies, spores from B. cereus ATCC strains 14579 and 9818, representative aerobic spore-forming bacteria found in milk, were similar to B. anthracis (Sterne) in their thermal resistance.