Needle-free connectors and cleaning devices
The needle-free connectors used in this study were a neutral displacement connector - MicroClave™ (ICU Medical) and a positive-displacement connector - CareSite™ (BBraun). Curos® caps containing 70% (v/v) IPA (3 M Healthcare) were compared to 2% (w/v) CHG in 70% (v/v) IPA wipes (Sani-cloth CHG 2%, PDI) for decontamination of the needle-free connectors.
Contamination of needle-free connectors
An overnight culture of Staphylococcus aureus National Collection of Type Cultures (NCTC) 6538 on tryptic soy agar (Oxoid) was used to prepare a 1 × 108 CFU/mL suspension in tryptone sodium chloride (1 g/L tryptone [Oxoid], 8.5 g/L NaCl [Sigma-Aldrich] in distilled water) containing 3 g/L bovine albumin faction V [VWR International] and 3 ml/L defibrinated sheep blood [TCS Biosciences] in accordance with BS EN 16615:2015 .
Following one activation of each connector, the external injection port of each sterile needle-free connector were inoculated with a 50 μL suspension containing at least 5 × 106 CFU of S. aureus and allowed to air dry for 4 h at 20 °C. Whilst the high inoculum of S.aureus used in this study would not be expected in the clinical scenario, it permitted the identification of any differences present between the two decontamination methods, was also representative of European standard antiseptic test conditions , and simulated a worst-case scenario in the clinical situation.
Evaluation of the variability in wiping technique by different operators
Needle-free connectors were cleaned for 15 s (through 180° 15 times) with a 2% (w/v) CHG in 70% (v/v) IPA wipe and allowed to dry for 30 s (this method was completed independently by two different experienced operators). A total of 54 of each type of needle-free connnector were studied (27 of each needle-free connector by each operator).
Evaluation of the prolonged effect of the decontamination procedures
Disinfection caps were attached to the needlefree-connectors for 1, 3 or 7 days and were compared with needle-free connectors cleaned with a 2% (w/v) CHG in 70% (v/v) IPA wipe. All the needle-free connectors were subsequently left at 20 °C in air for 1, 3 or 7 days. A total of 54 of each needle-free connector were studied per time point following each decontamination procedure. An identical number of control needle-free connectors which were contaminated as above and which were not decontaminated were also similarly studied and acted as positive controls for each sampling point.
Evaluation of the effect of a pre- and post-device activation wipe
Following contamination with S. aureus, 54 of each type of needle-free connector were cleaned as above for 15 s with a 2% (w/v) CHG in 70% (v/v) IPA wipe and allowed to dry for 30 s. These were then incubated for 7 days at 20 °C and then cleaned again with a 2% (w/v) CHG in 70% (v/v) IPA wipe prior to microbiological sampling.
Microbiological sampling of needle-free connectors
Needle-free connectors were immersed into bijous containing 1 mL of neutralizing solution consisting of 30 g/L Tween 80, 30 g/L saponin, 3 g/L lecithin, 1 g/L L-histidine, 5 g/L sodium thiosulphate in tryptone sodium chloride (all VWR International). Nullification of antimicrobial activity and non-microbial toxicity was verified prior to commencement of the study (unpublished data). The bijous were then sonicated for 10 min at 50 Hz. The entire volume of neutralizing solution was inoculated (in addition to dilutions from positive control connectors) onto chromogenic S. aureus plates (ChromID S. aureus [Biomerieux]) in duplicate.
Sample size calculation and statistical analysis
The aim of the study sample size was to demonstrate that each decontamination method achieved a 5 log10 reduction in the number of S. aureus (or 99.999% reduction). Based on preliminary work, it was concluded that 54 of each type of needle-free connector in each scenario should give at least a 90% chance of achieving a 5 log10 reduction in CFU. Median log10 reductions and 95% confidence interval (CI) were calculated and data analyzed using the Mann-Whitney test. The level of significance was < 0.05.