Support of vital body functions is the essence of the care of severely and critically ill patients. Use of mechanical ventilation and dialysis is life saving but also increases the risks for complications, above all secondary infections. Medical technical devices, apparatus as well as single use articles should be as safe as possible to use. Our group has two lines of interest both aiming at prophylaxis against secondary health related infections in serious ill patients. 1 Use of probiotic bacteria (such as the ProViva bacterium – L. plantarum 299v) for reduction of colonisation and overgrowth of pathogenic bacteria in the oropharynx and the deeper airways. 2 Studies on properties of materials used for invasive procedures, such as central venous catheters (CVC) and endotracheal tubes (ETT) used when patients are mechanically ventilated. Adhesion of bacteria and ability to withstand such adhesion, development of biofilm and tissue compatibility are being studied.