Microbial biofilms on needleless connectors for central venous catheters: comparison of standard and silver-coated devices collected from patients in an acute care hospital

Abstract

Microorganisms may colonize needleless connectors (NCs) on intravascular catheters, forming biofilms and predisposing patients to catheter-associated infection (CAI). Standard and silver-coated NCs were collected from catheterized intensive care unit patients to characterize biofilm formation using culture-dependent and culture-independent methods and to investigate the associations between NC usage and biofilm characteristics. Viable microorganisms were detected by plate counts from 46% of standard NCs and 59% of silver-coated NCs (P=0.11). There were no significant associations (P>0.05, chi-square test) between catheter type, side of catheter placement, number of catheter lumens, site of catheter placement, or NC placement duration and positive NC findings. There was an association (P=0.04, chi-square test) between infusion type and positive findings for standard NCs. Viable microorganisms exhibiting intracellular esterase activity were detected on >90% of both NC types (P=0.751), suggesting that a large percentage of organisms were not culturable using the conditions provided in this study. Amplification of the 16S rRNA gene from selected NCs provided a substantially larger number of operational taxonomic units per NC than did plate counts (26 to 43 versus 1 to 4 operational taxonomic units/NC, respectively), suggesting that culture-dependent methods may substantially underestimate microbial diversity on NCs. NC bacterial communities were clustered by patient and venous access type and may reflect the composition of the patient's local microbiome but also may contain organisms from the health care environment. NCs provide a portal of entry for a wide diversity of opportunistic pathogens to colonize the catheter lumen, forming a biofilm and increasing the potential for CAI, highlighting the importance of catheter maintenance practices to reduce microbial contamination.

FIG 1

Biofilm bacterial community compositions for selected needleless connectors. Each bar represents all taxonomic units that constituted ≥1% of the total number of sequences for each needleless connector sample. Sequence data <1% of the total were grouped together in the category “other.” Operational taxonomic units were defined to the species level if possible and to the family or genus level in other cases.

FIG 2

Weighted principal coordinate analysis (PCoA) plot of biofilm bacterial communities on selected needleless connector samples, as determined using QIIME. NCs 25 and 40 were from different patients. NCs 54, 55, and 56 were from different lumens of the same catheter in a single patient. NCs 62 and 63 were also from different lumens of the same catheter in a single patient. PC, principal coordinate.