Association of chlorination and UV irradiation to increasing antibiotic resistance in bacteria

In spite of widespread concern, there is no evidence in the scientific literature that warrants concluding that the use of chlorine or UV irradiation in industry or in the home has resulted in the emergence of mutant bacterial populations resistant to these disinfectants. At working concentrations, these disinfectants remain highly effective. The use of chlorine continues to result in significant reductions of pathogens in industry and in the home. The appropriate use of UV irradiation still results in significant decreases of bacterial pathogens in both the water treatment and medical industries. In addition, neither chlorination nor UV disinfection has been shown to result in the emergence of significant antibioticresistant bacterial populations in the home or in industry. Disinfection practices that result in significant reductions of pathogenic microbial populations reduce the risk of disease and, hence, reduce reliance upon antibiotics. This effect is very important as the trend of increasing antibiotic resistance is thought to be due to the overuse of antibiotics in both human and animals as well as noncompliance by patients suffering from infectious diseases. Although both chlorine and UV light are quite efficacious, the mode(s) of action are quite different. Chlorine is a multitarget disinfectant that affects several cellular constituents. Hence, single mutations are unlikely to result in a significant increase in resistance in a microorganism. Tolerance to chlorine is usually mechanical in nature and has never been demonstrated to be transferred on a plasmid. UV radiation used for disinfection purposes is in the UV-C range, which damages cells primarily by causing the formation of pyrimidine dimers in DNA and RNA. Nature has been using both means of killing bacteria for millions of years. Chlorine as hypochlorous acid has been used for countless years by white blood cells for disinfection purposes. Although UV-C radiation does not reach the earth's surface, sunlight also owes part of its disinfecting power to the formation of pyrimidine dimers. Bacteria have been exposed to sunlight for millions of years but sunlight still has considerable disinfecting power.