Implications of Limits of Detection of Various Methods for Bacillus anthracis in Computing Risks to Human Health

Abstract

Used for decades for biological warfare, Bacillus anthracis (category A agent) has proven to be highly stable and lethal. Quantitative risk assessment modeling requires descriptive statistics of the limit of detection to assist in defining the exposure. Furthermore, the sensitivities of various detection methods in environmental matrices are vital information for first responders. A literature review of peer-reviewed journal articles related to methods for detection of B. anthracis was undertaken. Articles focused on the development or evaluation of various detection approaches, such as PCR, real-time PCR, immunoassay, etc. Real-time PCR and PCR were the most sensitive methods for the detection of B. anthracis, with median instrument limits of detection of 430 and 440 cells/ml, respectively. There were very few peer-reviewed articles on the detection methods for B. anthracis in the environment. The most sensitive limits of detection for the environmental samples were 0.1 CFU/g for soil using PCR-enzyme-linked immunosorbent assay (ELISA), 17 CFU/liter for air using an ELISA-biochip system, 1 CFU/liter for water using cultivation, and 1 CFU/cm 2 for stainless steel fomites using cultivation. An exponential dose-response model for the inhalation of B. anthracis estimates of risk at concentrations equal to the environmental limit of detection determined the probability of death if untreated to be as high as 0.520. Though more data on the environmental limit of detection would improve the assumptions made for the risk assessment, this study's quantification of the risk posed by current limitations in the knowledge of detection methods should be considered when employing those methods in environmental monitoring and cleanup strategies.

Decontamination of Bioaerosols within Engineering Tolerances of Aircraft Materials

“…These recovery efficiencies are greatly by the fomite survival studies, which are greatly impacted by surface characteristics, relative humidity, and temperature (Sinclair et al, 2008). They concluded, however, that a low concentration release would be more likely detected by symptoms than using current sampling technology (Herzog et al, 2009 have been numerous other studies evaluating the best methods for collecting and analyzing these samples. Recent research on wipe and air sampling is discussed more in-depth below.…”

“…For example, Herzog et al (2009) Bacillus anthracis spore would constitute an unacceptable risk. Detection would be very difficult at these low concentrations.…”

“…CFU per 100 grams of soil; however, this type of sampling is highly dependent on sample pretreatment so there was a range of nine orders of magnitude because of the different approaches (Herzog et al, 2009). Finally, the BiSKit method was found to have the highest recovery for swipe samples, with recovery efficiencies for the fomite studies ranged from 10 to 50% and the extraction efficiencies ranging from 75 to 99%.…”

“…Sterilization is a procedure that kills all microorganisms, including high numbers of bacterial endospores, while disinfection is less lethal than sterilization, eliminating nearly all recognized pathogenic microorganisms, but not ensuring "overkill" and lacking the margin of safety achieved by sterilization procedure because spores are not inactivated (Chosewood and Wilson, 2009 suggesting that a 12-log reduction is required; however, most field trials have targeted a 6-log reduction (Gale et al, 2009). Others have said that any detectable Bacillus anthracis spore would constitute an unacceptable risk (Herzog et al, 2009).…”

“…It is important to note, however, that decontamination is generally referred to as a "process making material safe by absorbing, destroying, neutralizing, rendering harmless, or removing chemical or biological agents and radiological contamination" (DoD, 2009) and that most field tests have targeted a 6-log reduction in the contaminant (Gale et al, 2009). Others have stated that any detectable Bacillus anthracis spore would constitute an unacceptable risk (Herzog et al, 2009); however, this does not take into normal environmental risks in that these spores are indigenous in certain areas (Chosewood and Wilson, 2009 requires the decontamination methods be effective against spores, and more specifically, Bacillus anthracis spores. These spores are the target because it they are considered the most difficult biological warfare agent to decontaminate.…”