Mechanisms of killing of Bacillus subtilis spores by Decon and OxoneTM, two general decontaminants for biological agents

Abstract

Aims: To determine the mechanisms of Bacillus subtilis spore killing by and resistance to the general biological decontamination agents, Decon and Oxone TM . Methods and Results: Spores of B. subtilis treated with Decon or Oxone TM did not accumulate DNA damage and were not mutagenized. Spore killing by these agents was increased if spores were decoated. Spores prepared at higher temperatures were more resistant to these agents, consistent with a major role for spore coats in this resistance. Neither Decon nor Oxone TM released the spore core's depot of dipicolinic acid (DPA), but Decon-and Oxone TM -treated spores more readily released DPA upon a subsequent normally sublethal heat treatment. Deconand Oxone TM -killed spores initiated germination with dodecylamine more rapidly than untreated spores, but could not complete germination triggered by nutrients or Ca 2+ -DPA and did not degrade their peptidoglycan cortex. However, lysozyme treatment did not recover these spores. Conclusions: Decon and Oxone TM do not kill B. subtilis spores by DNA damage, and a major factor in spore resistance to these agents is the spore coat. Spore killing by both agents renders spores defective in germination, possibly because of damage to the inner membrane of spore. Significance and impact of study: These results provide information on the mechanisms of the killing of bacterial spores by Decon and Oxone TM .

Decontamination Options for Bacillus anthracis -Contaminated Drinking Water Determined from Spore Surrogate Studies

“…Earlier publications are somewhat contradictory regarding reported results using the peroxy-based compounds VirkonS (8,9,25) and Oxone (15,27). The results reported here show these compounds are not as effective as the other oxidizers tested for use as biocides for the types of spores and at both spore concentrations evaluated for drinking water treatment.…”

“…Given the slight differences we observed between the two spore surrogates evaluated, it is recommended that the same tests as those described here be replicated using virulent B. anthracis or avirulent B. anthracis strain Sterne spores to more definitively evaluate the results. The literature suggests that differences in spore preparations, including the temperature of the preparations, may account for differences in susceptibility when trying to evaluate decontamination effectiveness with surrogates, and even when B. anthracis or B. anthracis strain Sterne spores are used (26,27). Differences in resistance to various oxidants have been observed between alpha/beta-type spores, wild-type spores, and spores lacking both the alpha/beta-type SASP and the recA gene (27).…”

“…Liquid hydrogen peroxide/peroxyacetic acid (known as peroxy compounds and marketed as ready-to-use solutions), generally with a 15-to 20-min wet contact time and concentration as specified by the manufacturer, has also been recommended (13). Other products, such as hydrogen peroxide solution (3 to 25%) and potassium peroxymonosulfate, have been evaluated for efficacy against Bacillus spores as well (27). Although disinfectants at various concentrations have been tested previously against the spores of B. anthracis and their surrogates, wide variations in test protocols make meaningful comparisons among studies virtually impossible (9,11,17).…”

“…Specific amounts of quencher varied from 0.1 to 0.005 ml for sodium thiosulfate and from 0.005 to 0.75 ml for catalase. The use of sodium thiosulfate as well as catalase as a quencher for these types of experiments is well documented in the literature (3,10,27).…”

From Rings to Layers: Surprising Patterns of Protein Deposition during Bacterial Spore Assembly

“…1.) The coat has critical roles in protecting the spore from a variety of toxic molecules (6,25,32,33,39,40) and in facilitating germination (1,3,4,9). The coat is very likely to have additional functions as well, including the ability to act as an elastic material (7,10) and the ability to perform enzymatic reactions (14,15,19,24,26).…”