Photodynamic coatings kill bacteria on near-patient surfaces in intensive care units with low light intensities

Abstract

Surfaces in close proximity to patients within hospitals may cause healthcare-associated infections. These surfaces are repositories for pathogens facilitating their transmission among staff and patients. Regular cleaning and disinfection of these surfaces provides only a temporary elimination of pathogens with inevitable recontamination. Antimicrobial coatings (AMC) of such surfaces may additionally reduce the risk of pathogen transmissions. The study aimed to find out whether photodynamic coatings can be effective even at very low light intensities. To evaluate the efficacy of a standard and a novel photodynamic AMC in a field study conducted in two ICUs at our university hospital. The microbial burden was determined on three coatings: standard photodynamic AMC (A), a novel photodynamic AMC (B), and an inactive AMC as control (C). The control coating C was identical to standard coating A, but it contained no photosensitizer. During a 3-month period, 699 samples were collected from identical surfaces using eSwab and were analyzed (cfu/cm2). Mean values of all surfaces covered with control coating (C) showed a microbial burden of 5.5 ± 14.8 cfu/cm2. Photodynamic AMC showed significantly lower mean value of 1.6 ± 4.6 CFU/cm2 (coating A; p<0.001) and 2.7 ± 9.6 (coating B; p<0.001). When considering a benchmark of 2.5 cfu/cm2, the relative risk for higher microbial counts was reduced by 52 % (coating A) or 40 % (coating B), respectively. Both photodynamic AMCs offer a substantial, permanent risk reduction of microbial counts on near patient surfaces in ICUs with low light intensities.