Reply to why use tap water by Nagoba et al. - Explanation in physiological and microbiological view.

Dear Editors, The recent letter to the journal entitled ‘Irrigating methicillin-resistant Staphylococcus aureus-colonised and -infected chronic wounds – why use tap water?’ by Nagoba et al. (1) provides an opportunity for a deeper discussion from different perspectives. After the Second World War, advancement of water purification has greatly reduced human disease. Especially in the recent 10 years, more and more articles were published stating that tap water could provide better cleaning and clear results to improve wound healing. According to The Cochrane Collaboration, the infection rate after tap water irrigation was very low when compared with using other liquids (2), and no significant infection was found. The findings still support the view of applying tap water for wound cleaning. It is impossible to be free from bacteria in our environment, which can be found everywhere even in boiled water and sterile saline. But with the feature of continuous running, massive amount of tap water applied to wound surface, it is conducive to decrease wound contamination and colonisation. Some might wonder why not use other liquids such as mineral water and distilled water. The primary considerations are the easy access of the liquids and the volume being available. Asmost mineral water and distilled water are sold in a polyvinyl chloride (PVC) bottle without purification treatment (3) and are stored-to-be-sold for a period of time, they might contain impurities or microorganisms. The harmful residues might also be released by bottling containers enriched with CO2 (3). In addition, the large number of PVC bottles left behind after the wound irrigation becomes another kind of pollution and increases the costs of treatment. From our point of view, contamination, colonisation and biofilm production have always been the cause of non-healing wounds. Applying running tap water could soften biofilm, which is always produced on the surface of wounds as matrix (4). Furthermore, the impulsive force of water can reduce extracellular polymeric substance, which is a kind of harmful material of biofilm causing non-healing wounds (4). In addition, tap water irrigation could also decrease the risks of wound contamination and colonisation. After undergoing haemorrhoidectomy, taking sitz bath with warm water can avoid wound contamination and colonisation. Last but not least, applying warm tap water can further induce vessel dilation and provide better circulation around the wounds. Although boiled water is also an ideal method to clean up dirty wounds, it is not comparable to running tap water in terms of availability and convenience. Therefore, with a complete purification system, running tap water is acknowledged to be an option available for wound cleansing treatment.