The antibacterial properties of sodium hypochlorite and sodium dichloroisocyanurate as hospital disinfectants

Summary The antibacterial activity of unbuffered sodium dichloroisocyanurate (NaDCC) (pH 6·6) and of sodium hypochlorite (NaOCl) buffered to pH 7·2, 9·0 and 10·6 was compared. Under clean conditions, solutions of NaDCC at pH 6·6 or NaOCl at pH 7·2 and 9·0 with 100–200 mg l −1 available chlorine showed satisfactory disinfectant activity against vegetative bacteria. Sporicidal action required higher concentrations of both agents, and NaOCl at pH 7·2 showed most activity. In the presence of organic matter NaDCC offers significant advantages over NaOCl, a 3000 mg l −1 solution of NaDCC giving satisfactory activity in the presence of plasma concentrations up to 20% v/v compared with NaOCl solutions at pH 7·2, 9·0 and 10·6 which were inactivated at chlorine concentrations up to 5000 mg l −1 . Although NaOCl pH 10·6 showed satisfactory disinfectant activity under clean conditions, our results indicate that formulations at this pH should not be used where sporicidal action is required or where substantial organic soiling is anticipated.