by Elio Schaechter and Joshua Fierer
Newspapers and other media are reporting with regular frequency that restrooms, ATM machine pads, money bills, and other sites carry many different microbes upon their surfaces including potentially pathogenic bacteria and viruses. Headlines call attention to such scary-sounding news and alarm the general public. We can expect that this practice will engender a widespread concern of the public for their safety. The outcry will encourage the implementation of unreliable, unnecessary, and potentially counterproductive “protective” measures. People may, for example, resort to using soaps with bactericidal compounds that have the potential to alter the generally protective normal flora. Inappropriate or non-essential use of bactericides may well accelerate the development and spread of resistance to microbicides and antibiotics within the microbial community. Resistance capabilities, including the upregulation of efflux pumps, can evolve particularly rapidly, and these same mechanisms may also increase resistance to antibiotics. For a reference to this topic, click here.
Let us suppose, as implied by these reports, that we do often encounter potential pathogens on ‘fomites,’ that is, inanimate objects. This is nothing new.
We have known for over one hundred years that we live in a buggy world, surrounded by actual and potential pathogens, and that we often carry them within us. How often do we get sick from such encounters? Only the most immunosuppressed people must live in an aseptic “bubble” to avoid contact with all environmental microbes. With the exception of some epidemic-type diseases such as the common cold and influenza, most of us living in hygiene-blessed environments lead a life relatively free of externally-acquired infectious disease. In micro classes for medical students, we used to quip that the only people who get sexually transmitted diseases from toilet seats are members of the clergy! The exceptions to such relatively peaceful coexistence are important, viz. the spread of MRSA or Clostridium difficile in hospitals and, of recent, in the community, but these are specific concerns requiring their own focus when epidemiological studies indicate there is a problem.
The studies underpinning these scary headlines commonly involve analysis and/or amplification of the DNA that can be swabbed from surfaces. This methodology does not assess the viability of the organisms nor do these studies necessarily estimate the amount of specific DNA present. It is obvious that not knowing if the agents are alive or dead or if they’re present in amounts that could initiate an infection impacts on conclusions about the danger they may pose.In other words, there is no basis for linking these findings to the realities of public health.
Of particular concern to us, the authors of these scientific articles do not, in general, acknowledge their limitations. Instead, we read such statements as: More generally, this work is relevant to the public health field as we show that human-associated microbes are commonly found on restroom surfaces suggesting that bacterial pathogens could readily be transmitted between individuals by the touching of surfaces. This research does provide potentially useful information by listing the vast number of bacterial species that are found in the human environment, many of human origin. However, this merely opens possibilities about their relevance to human health, and, broadly speaking, these facts are far from novel. Do the justifiable conclusions from these studies warrant alarming the public? We think not. We wish that the authors clearly pointed out the limitations of their studies.
Joshua Fierer is Chief of Infectious Diseases at the VA San Diego Health Care System and Professor of Medicine and Pathology, University of California at San Diego.