Tissue around catheters is a niche for bacteria associated with medical device infection

Abstract

To investigate whether pericatheter tissue is an additional niche for bacteria potentially causing catheter-associated infections in humans. Postmortem patient study. Intensive care unit, autopsy room, and microbiological laboratory in a university hospital. Eighteen deceased patients from whom 35 catheters plus surrounding tissues were collected. Under axenic conditions catheters and surrounding tissue were excised from deceased intensive care unit patients. The excised parts of the catheters and samples of surrounding tissue were quantitatively cultured and bacteria identified, and tissue histology/immunohistochemistry was performed. Nine of the 35 (26%) pericatheter tissue samples tested were highly culture positive. The corresponding catheter segments were culture negative or yielded only low numbers of bacteria. Bacteria cultured from different sites of the catheter and surrounding tissues almost all were coagulase-negative staphylococci (predominantly Staphylococcus epidermidis) and Enterococcus faecalis. In histology, bacteria were seen in tissue, intercellularly and associated with host phagocytes. Tissue surrounding biomedical devices forms a niche for bacteria. This is an as yet nonrecognized element in the pathogenesis of catheter-associated infections, with possible consequences for strategies of prevention and treatment of these infections.