Methods and apparatus for preventing patient bloodstream infection by microorganisms during administration of various medications or fluids through IV lines. In particular, the invention reduces contamination of IV lines, connecters, stopcock valves, manifolds, ports, etc. by means of irradiation by violet and/or blue light. Each embodiment comprises a source of violet and/or blue light and an optical element optically coupled to that light source for shaping the radiation pattern of the light emitted by the light source. Preferably, a light-emitting diode or a laser diode that emits light in the desired wavelength can be used. The optical element, optically coupled to the light source, is embedded or installed in or attached to a component of an IV set, the emitted light being directed to a "point of entry" or any other stagnation point of an IV set.
