Methods and apparatus for the inactivation of infectious agents in, on or around a catheter residing in a patient's body cavity. The method comprises a coupling adapter for facilitating the transmission of non-ultraviolet sterilizing electromagnetic radiation (EMR) substantially axially along an optical element into the catheter body. Through delivery of the sterilizing EMR to particular areas of highest infection, the present disclosure is able to inactivate the major sources of infection in catheters.