Deposits on the intraluminal surface and bacterial growth in central venous catheters

Central venous catheter (CVC) tip and blood cultures are generally used to diagnose a catheter-related infection. Such methodology does not confirm the presence of bacterial colonisation on parts of CVCs other than the CVC tip. In order to assess the extent of bacterial colonisation, 10 catheters were examined in detail from patients admitted to intensive care unit. Swabs from the lumen at several sites (hub, indwelling and non-indwelling) were cultured and the intraluminal surface of the device subjected to scanning electron microscopy (SEM). Bacteria were detected on five out of 10 catheters (50%), and bacterial contamination of CVCs was common in the hub area of the device. Deposits (crystallisation) that differed from bacterial colonisation or biofilm were observed on the intraluminal surface of used CVCs. SEM showed bacteria firmly anchored to the deposits. Experimental flow studies demonstrated that deposits were more likely to appear after exposure to solutions such as total parenteral nutrition rather than distilled water. These deposits facilitated bacterial colonisation 30 times more than CVCs free from deposits.