It’s Gettin’ Hot and Humid in Here

Courtesy Photo | Tony Buhr, Ph.D., a biologist at NSWCDD, works at a biological safety cabinet on DTRA-funded work on biological warfare agents.  

FORT BELVOIR, VA, UNITED STATES

06.04.2019

Courtesy Story

Defense Threat Reduction Agency's Chemical and Biological Technologies Department

It’s a typical August afternoon in the southeastern U.S. The hot, humid air is thick enough to slice with a knife. Everyone feels somewhere between uncomfortable and miserable. Now imagine if it were humid and 170 degrees Fahrenheit as in a sauna. Though this high heat and humidity would agonize most people and stall machinery operation, it kills biological warfare agents (BWAs): potentially deadly biological toxins, like anthrax, that could directly threaten the health and security of our warfighters.

Scientists are optimizing ways to use hot, humid air to decontaminate equipment that warfighters use, such as an aircraft. Past biological warfare attacks emphasize the need to detect and decontaminate critical facilities and equipment in the shortest time possible. Thanks to the joint research effort between the Defense Threat Reduction Agency’s Chemical and Biological Technologies Department (DTRA CB) and Naval Surface Warfare Center Dahlgren Division (NSWCDD), a new solution has come to the forefront. Managed by Glenn Lawson, Ph.D., with DTRA CB, and led by biologist Tony Buhr, Ph.D., with NSWCDD, the study explores making BWAs more susceptible to death at lower temperatures.

BWAs are living organisms — e.g., bacteria, toxins, viruses — that multiply once within their animal hosts. This can cause a range of harm to people — from mild, allergy-like symptoms to death. When agents such as anthrax become weapons of war, they affect not only people but also equipment used by warfighters. Anthrax lingers quietly through various environmental conditions and becomes active only when the setting is right, such as through skin contact or inhalation. Therefore, sterilizing surfaces contaminated with BWAs is key to survival. Unfortunately, bleach and other corrosive chemicals typically used to inactivate BWAs can damage or destroy modern military equipment. Made of advanced materials and sensitive electronics, they cannot withstand a chemical scrub down and still maintain peak functionality. Fortunately, there’s another decontamination method: one that uses hot and humid air. It’s called the Joint Biological Agent Decontamination System (JBADS).

After extensive research, the Air Force Research Laboratory demonstrated the effectiveness of the JBADS, a system that provided the military services with an urgently needed hot-air decontamination (HAD) capability. Conceptually, the HAD method forces hot, humid air into the interior and onto the exterior of the contaminated equipment to inactivate BWAs. JBADS uses HAD, operates within an enclosure big enough to house an aircraft and produces air of 170–180 degrees Fahrenheit (75–80 degrees Celsius) and 90 percent relative humidity. While it reduces BWA concentrations to below infectious levels, the JBADS process is resource and time intensive and takes several days to complete. Any reduction in the thermal and temporal conditions required for decontamination would conserve time and resources, and that is what Lawson and Buhr aim to achieve. The first step? Manipulating the bacteria itself.

Bacteria similar to anthrax produce two types of cells: 1) vegetative (or growing) cells and 2) dormant, environmentally resistant spores. Vegetative cells are viable only in a narrow environmental range while spores are dormant and designed to endure a wide range of conditions. Spores have thick protein and carbohydrate outer layers (called the cortex and coat) that protect them from light, heat and toxicity. As a result, they can remain inactive (but not die) in water, soil or air until a return to conditions that support vegetative growth, such as inside a human body. There, spores become vegetative cells and replicate. Because vegetative cells cannot survive high heat and humidity, Lawson and Buhr developed two objectives for their study: 1) cause spores to become vegetative cells outside the human body — i.e., before they can cause harm — and 2) kill vegetative cells using HAD. To do this, they first sprayed a bacteria laden labware with a germinant mixture to transform spores into vegetative cells. After a short incubation time, they applied HAD using JBADS. They hoped to kill 99.9% of spores within 24 hours and at or below 140 degrees Fahrenheit (60 degrees Celsius).

To meet their objectives, Lawson and Buhr are using the design-of-experiments (DOE) method to arrive at the perfect set of conditions that achieve the desired outcome of 99.9 percent decontamination. DOE is a statistical method that identifies how multiple variables in a study influence the outcome of interest.

Lawson and Buhr have found the perfect combination of three variables to effectively decontaminate spore cells: 1) the time required to kill vegetative cells, 2) the degree of heat needed to kill the vegetative cells and 3) the relative humidity needed to accompany the heat. So far, laboratory test results with anthrax like organisms have demonstrated that a single application of the germinant, followed by HAD, could inactivate more than 99 percent of spore cells. A repeat germinant application can achieve the objective of 99.9 percent decontamination at the preferred temperature and in less time.

Over the next year, Lawson and Buhr will collect and analyze more data to develop technologies that reduce the JBADS decontamination timeline. For now, they have shown that the application of a germinant makes bacterial spores easier to kill. Overall, this supports critical equipment decontamination and a quicker return to operations, using less resources, to support warfighter readiness and mission success.

POC: Glenn Lawson, Ph.D.; [e-mail]

• Date Taken: 06.04.2019
• Date Posted: 06.04.2019 15:19
• Story ID: 325341
• Location: FORT BELVOIR, VA, US