a bactericidal composition and method for inhibiting and controlling the growth of the capsulated , facultative bacterium , klebsiella pneumoniae , are disclosed . the composition comprises an amount , effective for the intended purpose , of 2 - ethanamine hydrochloride and n - tri butyl tetradecyl phosphonium chloride . the method comprises administering between about 0 . 1 to about 200 parts of this combined treatment to the particular water containing system for which treatment is desired .