ADVANCEMENT OF THE PRACTICE
Open Access
THE PRACTITIONER’S TOOL KIT
Estimating Microbial Bioloads
James J. Balsamo, Jr., MS, MPH, MHA, RS, CP-FS, CSP, CHMM, DEAAS Nancy Pees Coleman, MPH, PhD, RPS, RPES, DAAS
Brian Collins, MS, REHS, DLAAS Gary P. Noonan, CAPT (Retired), MPA, RS/REHS, DEAAS Robert W. Powitz, MPH, PhD, RS, CP-FS, DABFET, DLAAS Vincent J. Radke, MPH, RS, CP-FS, CPH, DLAAS Charles D. Treser, MPH, DEAAS
Editor’s Note: The National Environmental Health Association (NEHA) strives to provide relevant and useful information for environmental health practitioners. In a recent membership survey, we heard your request for information in the Journal that is more applicable to your daily work. We listened and are pleased to feature this column from a cadre of environmental health luminaries with over 300 years of combined experience in the environmental health field. This group will share their tricks of the trade to help you create a tool kit of resources for your daily work. The conclusions of this column are those of the authors and do not necessarily represent the ocial position of NEHA, nor does it imply endorsement of any products, services, or resources mentioned.
spate of viral diseases. To make this task easier, we can use a simple tool to estimate microbial populations, which helps us under- stand the biosphere outside the laboratory. The term bioload was introduced some- time in the 1960s by Dr. Velvl William Greene (1928–2011) when he began working for the Planetary Quarantine Division of the National Aeronautics and Space Administration (NASA) in an exobiology program. He used the word bioload to dierentiate from bioburden. Bio- load refers to an estimation of the number and types of microbes in a specific environment. This estimate is based on the knowledge, skill, and large doses of logic in environmental health science. Conversely, bioburden refers to the actual number of microbes determined by viable sampling assays. While the bioburden gives us an incident snapshot, the bioload estimate provides us with a predictive model of the prevalence of microbes in any given biosphere. Unbelievably, if we actually sample the various surfaces, air, water, and dynamics in the environment, our bioload estimates are quite accurate. For this reason, we found that by developing a bioload profile, our accuracy in inspections, audits, and evaluations is significantly enhanced. For example, if we were to estimate the number of microbes that would be present in an occupied elementary school classroom for purposes of decontamination, our predictive model or bio- load estimate would place the highest number of viable organisms on the desks and tables directly in front of the children, due to their normal activity. Other surfaces of concern such as common touch or high touch objects includ- ing doorknobs, push plates, sink faucets, and toys would naturally have a lower bioload. And
T here is a certain approach and logic to assessing microbiological risk in our practice. While most of us are concerned about compliance with regulatory requirements, the sciences supporting those mandates are based on experimentation and observation and conform to applied contami- nation control axioms. Much of the work we do in contamination control has its founda- tion in environmental microbiology. As such, the greater part of our professional expertise is directed at controlling the less than 1% of all bacteria—as well as other microorgan- isms—that can potentially be pathogenic. We also concern ourselves with microbes that cause destruction, decay, decomposition, and conditions that we find unpleasant and unwanted. In so doing, we routinely confront situations where living things can thrive in an infinite number of environments, multiply exponentially, demonstrate uncanny surviv- ability skills, move through impenetrable barriers, and do so without us being able to see them with the unaided eye. For these rea- sons, we need to objectively assess the micro- biological problems confronting us. We begin by surveying the immediate area of concern and assessing both the macro-
and micro-environments that might influ- ence growth and movement. This approach is quite similar to the one we take with inte- grated pest management, except at a macro level, with the realization that every undesir- able microbiological condition is special and occurs in a unique environment. Together with this assessment and some understand- ing of microbial ecology, along with the influences of moisture, temperature, and substrate, we can begin to develop strategies to impact growth, survival, movement, and more importantly, control and prevention. The second task is to estimate the type and number of organisms that are part of the macro- and micro-environments of concern. The more we know of their number and sur- vival strategies, as well as population dynam- ics, the better we can predict the risk of infec- tion and eect scientifically based rational controls in both cost-eective and cost-e- cient ways. These estimates are particularly valuable in providing information on trac patterns in food production and in all types of institutional uses, particularly when we are trying to determine the origin and movement of ubiquitous organisms such as Listeria , Legionella , Clostridia, and the more recent
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Volume 87 • Number 1
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