On the opening leaf of his seminal text on Ecology, Eugene Pleasants Odum wrote:
Big fleas have little fleas
Upon their backs to bite ’em,
And little fleas have lesser fleas,
and so, ad infinitum.
This little Dutch proverb tells us that there is no such thing as a single factor that has an absolute effect in the living world – ecology being what it is.
I’m not going to get into a dissertation on the value of environmental cleaning and the prevention of disease. We all know, or at least should know, that reducing the bioburden in any critical environment will affect both air- and surface-borne contamination. The reduction of the bioburden is indeed the cornerstone of contamination control science; be it institutions, food production or critical manufacturing of semiconductors, optics, space tools and pharmaceuticals, just to name a few.
However, when we regard the effects of the environment as the vehicle of disease such as MRSA, we need a bit of both introspection and circumspection and a lot less histrionics.
Beginning with the writings of Catherine Beecher, William Alcott, Sylvester Graham and John H. Crisom in the 1840s, the relationship of environmental sanitation and disease was well known and heralded the start of the sanitarian movement. Florence Nightingale in the Crimean War and the Sanitary Commission of the Civil War brought hospital sanitation, infection and soldier survivability to the forefront. What I now find most interesting is that we really haven’t learned a lesson from either science or history. The recent spate of MRSA infections have some of the latest treatises focusing on the “mop and magic juice” as the solution to diseases of public health importance, and fail to realize the effect of people’s behavior and movement on their transmission and dissemination.
As students in environmental microbiology, we unfortunately tend to think in a pure culture paradigm pioneered by Louis Pasteur and Robert Koch (which remains an important tool in clinical microbiology). We sample and isolate a pathogen and postulate that that organism is indicative of that environment. We coax it on an enriched agar and incubate it at body temperature, not realizing that it comes from an un-enriched substrate and is probably so stressed that any insult will render it harmless. Finding a disease organism on a Petri dish is all too often used as a segue for marketing “environmental” products.
Rather, we need to view the environment as processes of microbes that surround our biosphere. Two famous microbiologists of our last century pioneered the study of these processes: Sergius Winogradsky and Martinus Willem Beijerinck. Basically, they studied the relationships between different types of microorganisms in mixed communities; this is what we do, or at least what we should be doing.
If we apply our knowledge, we can postulate the dynamics of logarithmic microbial reduction in the absence of any disinfectant. We have references to d- and z-values for almost every pathogen and the environment in which they are found, as well as their stressors. A marvelous textbook, published in 1985 “Microbial Survival in the Environment, Bacteria and Rickettsiae Important in Human and Animal Health” by E. Mitscherlich, E. H. Marth details this quite nicely.
Couple this with Epidemiology the applied science that ranks the many factors in our environment in their relationship to the transmission of disease, we can do some pretty good public health in the cleaning industry without overkill or costly intervention. By studying the various diseases in a population, we can get clues whether the disease is spread by direct contact, airborne; via fomite, vehicle or vector. According to the experts (CDC), the spread of MRSA is predominantly through direct contact with an infected individual or carrier of the disease organism, and to a lesser degree: airborne (at least droplet spread). We know that high school and college wrestlers, drug users, those who are overly promiscuous sexually, have a higher incidence of this disease than the rest of the population. We also know that certain intrinsic factors such as resistance and human microbial ecology play an important role.
Epidemiology teaches us that in any population, MRSA is pervasive and omnipresent. Yet, not everyone who comes in contact with the organism will get the disease – even in the absence of cleaning. For example, how many people daily ride the subways in New York City, come in contact with the organism and do not contract the disease – and this is in the absence of any cleaning whatsoever? There is no epidemic amongst strap-hangers.
There is some indication in the literature that the medical profession helped create Methicillin resistance with overuse of antibiotics. I do not feel that we should contribute to this evolutionary trend by implicitly advocating treating every surface in which we come in contact, with a biocide. This is not to say that we shouldn’t clean. We should, but temper that cleaning with good environmental microbiology and the lessons taught to us by Epidemiology.
In the regard to MRSA: Hand washing is a learned behavior. B.F. Skinner showed us how to effectively change behaviors. We need to start there.