Microbial contamination on highly touched objects. I By: Jay A. Glasel Dr. Glasel is the managing member and founder of Global Scientific Consulting LLC. He is also a Professor Emeritus in the Department of Microbial, Molecular and Structural Biology at the University of Connecticut Medical/Dental School in Farmington, CT. Co-editor and an author for the Academic Press textbook Introduction to Biophysical Methods for Protein and Nucleic Acid Research, Dr. Glasel’s scientific research has been in the fields of struc-tural biochemistry, molecular immunology, pharmacology and cell biology. for more info Visit www.cmmonline.com and type in search keyword: Microbes . For more information on related products, visit www.cmmonline.com , select SUPPLIER SEARCH from the main navigation bar, and enter keyword: Disinfect . Increasing quantitative evidence points to the conclusion that children are more susceptible to infection by microbial pathogens picked up from their environments than older persons exposed to the same pathogens. There are many causes that underlie this increased risk, but probably the major one is that childrenʼs immune systems — the natural protec-tion against pathogens — donʼt fully develop until adulthood. The increased risk for infection combined with crowding in schools, the fact that children may not all have developed sanitary habits and have fre-quent hand-to-mouth and object-to-mouth con-tacts, etc., make it very important to understand what environmental sources present the most important risks for infection. If the properties of these pathogen sources can be understood, then cleaning and disinfection science may be used to minimize the risk for infection. Fortunately, scientific studies exist that have examined environmental microbial contamination in public places. The results of these studies are sometimes sur-prising. We all know that a major source of the spread of pathogens can be direct person-to-person transfer via sneezes and coughs. But, this is actu-ally a very inefficient way of transferring disease. A more efficient way is the transfer of human microbial pathogens to a surface or material that is touched by many other individuals, known as highly touched objects (HTOs), in the course of their daily lives and to allow each individualʼs touch-to-mouth or touch-to-hand-to-mouth prac-tice to spread infection. To be kept in mind is the fact that many individ-uals who are infected with pathogens donʼt nec-essarily become sick: They are “carriers.” The frequency of hand-to-surface and hand-to-mouth contacts has been quantitatively reported in a number of studies. These studies have shown that this behavior is age-related. For example, it was found that children less than 24 months old perform more than 80 hand-to-mouth actions per hour while the average for children two to six years old is nine such events per hour. And the number of hand-to-surface events is very high for all ages. The high frequencies of these events highlight the efficiency of bidirectional transfer of pathogens from mouths to surfaces in daycare centers and in schools. But it brings up the questions of whether or not microbial pathogens can survive on surfaces, which surfaces have a high probability of harbor-ing microbial contamination and how can micro-bials best be removed from these surfaces. Fortunately, all of these questions have been addressed by quantitative scientific studies within the last few years. As far as the survival of pathogens on surfaces — scientists refer to an inanimate object that is con-taminated with pathogens as a fomite — is con-cerned, a very important and widely quoted recent paper reveals that viable common pathogens may persist on surfaces for times ranging from two hours to more than four years, depending upon the species. The range of persistences for pathogenic bacte-ria and viruses is given in Table 1. So the answer to the question, “Can viable microbial pathogens persist on surfaces ready to be touched and passed to the mouth?” is an empathetic, “Yes.” The next question is, “Which surfaces are most likely to harbor significant numbers of viable microbial pathogens?” The results of detailed scientific investigations that have focused on answering this question have also been published. The results of these studies are harder to inter-pret because the recovery methods data analysts use vary widely. Even so, some general conclusions can be drawn. One surprising conclusion is that restroom floors and walls do not rank at the top of the list of sources of potential microbial contamination, pos-sibly because most cleaning efforts are concen-trated there. www.cmmonline.com 11
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