State Of The Science: Do Disinfectants Cause Antibiotic Resistance? Most stepwise training studies have cen-tered on Triclosan, though Triclosan is a rel-atively uncommon active ingredient in sur-face disinfectants and is fundamentally more like an antibiotic than a typical bio-cide. That is, it appears to act on one target in a bacterium rather than multiple targets all at once (McMurray, Nature . 1998. 394:531-532). Since Triclosan is not frequently used as an active ingredient for surface disinfection, its discussion in this article is limited. With respect to surface disinfectants, the most relevant biocide that has been studied for cross-resistance potential is the quater-nary ammonium compound (QAC) or quat. QACs are one of the most common active ingredients in disinfectants today, especially in health care and commercial settings. Laboratory studies have shown that exposure of a bacterium called Pseudomonas stutzeri to QACs over time can result in increased resistance to certain antibiotics and other biocides (Tattawasart, Journal of Hospital Infection . 1999. 42:219-29). And genes have been identified that appear to be linked to the development of QAC resistance and corresponding resistance to some antibiotics (Russel, Journal of Applied Microbiology . 2002. 92:121S-35S). Triclosan-containing hand soap. Samples of bacteria from hands were collected at initiation of the study and after the one-year use period before being ana-lyzed for antibiotic resistance. No linkage was found between antimicro-bial use in the households and the rate of antibiotic-resistant bacteria isolated from hands. The findings of the 2005 Aiello, et al. study are generally representative of other real-world studies, though few have directly focused on the issue of cross-resistance. a safe bet is to utilize a surface disinfection technology that destroys many different components of a bacterium at once, leav-ing little opportunity for mutations and phys-iological changes that could result in cross-resistance to antibiotics. One example of such a technology is a steam vapor system. Steam vapor systems are finding more frequent use in hospitals, schools and food-service applications. In the context of cross-resistance, steam vapor has a key advantage in that it is a chemical-free disinfection approach, where heat transferred to microorganisms on the surface destroys many target sites at once. Since nothing is left behind, there is virtu-ally no risk of environmental development of cross-resistance. At least one device on the market has been tested extensively by independent laboratories (Tanner, American Journal of Infection Control . 2009. 37(1):20-27). Sodium hypochlorite or bleach is another example of a biocide that can be used regularly for indoor surface disinfection that acts against many different compo-nents of bacterial cells at once, reducing the likelihood of mutations that confer resistance. Bleach, in particular, is noteworthy because it has been used at low levels in water treatment for ages and reports of cross-resistance are scarce, if they exist at all. Interpretation One thing is clear: It is relatively easy to bring about cross-resistance in the labora-tory using carefully designed and controlled experiments. However, it is difficult to bring about or observe such a phenomenon under more realistic conditions. Most of the research that has been done thus far to explore the phenomenon of cross-resistance could be considered pri-mary in nature. That is, it has set out to answer funda-mental questions or observe phenomena that were expected to be readily observ-able. Researchers such as Aiello, et al., who have asked these tough questions and car-ried out well-designed, rigorous studies to evaluate their hypotheses, should be praised. They have contributed greatly to the overall understanding of surface disinfec-tion and its impact to antibiotic resistance. It would be foolhardy to think that cross-resistance does not take place to some extent in practice, but the current science suggests that the risk associated with not disinfecting contaminated surfaces far out-weighs the risks associated with cross-resistance. Disinfection brings many benefits to facil-ities. A number of studies suggest that the use of disinfectants in strict compliance with label instructions yields a benefit to facility occupants by breaking the infection cycle (Cozad, American Journal of Infection Control . 2003. 31:243-254). For cleaning professionals who are hyper-aware of the cross-resistance issue, The Science: Actual Usage A relatively small number of studies have evaluated the effect of biocide use on antibiotic resistance levels in real settings. No “smoking gun” studies showing cross-resistance are known at this time. Furthermore, no outbreaks of antibiotic-resistant microorganisms have been traced to sub-lethal disinfectant exposure in the environment. Of the few available studies, arguably the best designed and most comprehensive was done by Aiello, et al. in 2005. In this study, 224 households were ran-domized to use of a broad array of antimi-crobial cleaning products for one year (Aiello, Emerging Infectious Diseases . 2005. 11:1565-70). Products included oxygenated bleach, a quaternary ammonium cleaner and a Conclusion In many facilities today, decontamination of surfaces in environments where antibiotic resistance is prevalent is a paramount con-cern. Recent news articles with titles like “Disinfectants May Promote Growth of Superbugs” certainly grab attention, but current science does not support the notion that cross-resistance is a common phe-nomenon in practice. Cross-resistance can be readily demon-strated in the laboratory and it is reason-able to think that a low level of cross-resist-ance takes place in real life. However, the risks of not disinfecting environmental surfaces regularly to break the cycle of infection likely outweigh any risks associated with cross-resistance. CM 22 CM/Cleaning & Maintenance Management ® • July 2010
CMM – Archives July 2010: 22
