Center for
Biofilm
Engineering
An in vitro Comparison of Intraluminal Biofilm
Bacteria Transfer of Three Peripheral Intravenous
Valved Blood Control Catheters
RYDER SCIENCE, Inc.
…..medical biofilm research
Ryder M1, deLancey Pulcini E2, Parker A2, and James G2
(1) Ryder Science, Escondido, CA, (2) Center for Biofilm Engineering, Montana State University-Bozeman
INTRODUCTION
Blood exposure that might place healthcare personnel at risk for
HBV, HCV, or HIV infection is defined as a percutaneous injury (e.g.
a needlestick or cut with a sharp object) or contact of mucous
membrane or non-intact skin (e.g. exposed skin that is chapped,
abraded, or afflicted with dermatitis) with blood, tissue, or other
body fluids that are potentially infectious (MMWR, June 29,
2001/50(RR11);1-42).
The insertion of peripheral intravenous catheters (PIVC) is the most
common invasive procedure performed in hospitals. Preventing
bloodborne pathogen exposure to healthcare workers during
intravenous catheter insertion has been an ongoing challenge. The
new generation of PIVCs utilizes additional internal components
within the catheter hub to reduce blood exposure during insertion.
These components increase the internal surface area that is
thought to increase the potential for biofilm formation and
subsequent transfer of bacteria into the bloodstream. This raises
concern for an increased risk for bloodstream infection.
METHODS
At Time 96 hours, one of each catheter type was destructively
sampled (including all internal components; the hub, spike, septum,
etc.). Each part was vortexed, sonicated and vortexed again to
detach and disaggregate the biofilm to form a bacterial suspension
for viable plate counts (CFU/ml). One of each assembly type was
formalin fixed for scanning electron microscopy (SEM),
disassembled and imaged.
Statistical analyses were performed in Minitab v.16 by fitting
ANOVA models to the log densities (LDs) for each of the Flush 1,
Flush 2, or Sonicant data. The ANOVA included experiment as a
random effect; and time, "hub type", and the two-way interaction as
fixed effects. Since the interaction between time and "hub type"
was not significant, the main effects due to time and hub were
directly interpreted. A weighted ANOVA model was fit to the Flush 2
data to account for heteroscedastic variance of the LDs. Tukeys
multiple comparison method was used for all pairwise comparisons.
Statistical significance was determined with respect to a
significance level of 5% (95% confidence).
PURPOSE
The purpose of the this study was to compare the bacterial transfer
rate and intraluminal biofilm formation between three valved blood
control PIVCs in a clinically simulated in vitro model.
METHODS
Three PIVCs were tested: Smiths Medical ViaValve® Safety I.V.
Catheter, BD Insyte™ Autoguard™ BC Shielded I.V. Catheter and
the B. Braun Introcan® Safety 3 Catheter.
Six experiments were run with three time points measured within
each run: 0, 72 and 96 hours. Catheters were preconditioned with
Bovine Serum Albumin (BSA) using a pressurized serum bottle to
mimic venous insertion of the catheters.
RESULTS (cont.)
RESULTS
ViaValve® Safety I.V. Catheter
A
luer fitting inserted .208”
(halfway between ISO min &
max)
B
in back of
seal
BD Insyte™ Autoguard™ BC Shielded I.V. Catheter
A
in & around
plunger
B
In over six experimental runs, the bacterial log densities in Flush 1
and Flush 2 were compared among three catheters types: the
ViaValve®, Autoguard™ BC, and Introcan® Safety 3. In 4/2012,
three experiments were performed with the Autoguard™ BC and
ViaValve®. Three other experiments with the Introcan® Safety 3
and ViaValve® were run in 10/2012. In each experiment, the
bacterial log densities in Flush 1 and Flush 2 measured at three
different time points: 0, 72 and 96 hours.
in seal
in tube (entire
length not
shown)
in eyelet
in hub
B. Braun Introcan® Safety 3 Catheter
A
There were statistically significantly smaller bacterial mean log
densities in Flush 1 and Flush 2 for ViaValve® compared to either
the Autoguard™ BC (p-value = 0.003 and 0.001 respectively) or
Introcan® Safety 3 catheters (p-value = 0.014 and 0.010
respectively). There were no differences in the bacterial mean log
densities between the Autoguard™ BC or the Introcan® Safety 3 in
either Flush 1 or Flush 2 (p-value = 0.17 and 0.55 respectively).
In and around in tube (entire
plunger
length not
shown)
B
Figure 1. Preconditioning of catheters with albumin
prior to inoculation with Staphylococcus aureus.
in actuator in tube (entire
length not
shown)
For ViaValve®, the rate of decrease of the bacterial mean LD over
time was small but not statistically significant in either Flush 1 (0.11/day) or Flush 2 (-0.03/day). For the Autoguard™ BC, there
was a statistically significant rate of decrease over time in the
Flush 1 (-0.21/day) but not Flush 2 (-0.05/day). For the Introcan®
Safety 3, a statistically significant increase was found in both Flush
1 (0.71/day) and Flush 2 (0.91/day). The rates of change in
bacterial mean LD over time amongst the three catheters were not
significantly different in either Flush 1 (p-value ≥ 0.121) or Flush 2
(p-value ≥ 0.063).
in eyelet
in hub
Figure 4. A. Cross-sectional schematic of the catheter hub
accessed with syringe. B. Internal volume and surface area in
contact with blood (in red). Blood locations used to calculate
surface area and volume in Table 3.
After preconditioning, a needleless connector (SmartSite®) was
attached to each catheter, inoculated by flushing with 0.5 ml of a 104
colony forming units per ml (CFU/ml) of Staphylococcus aureus, and
incubated at room temperature for 2 hours.
Comparison for Surface Area (in2) and Biofilm Count (CFU)
4.90
Internal Surface Area (in²)
5.0
Log Sum CFU
4.02
4.5
3.84
4.0
3.5
Table 1. Yellow indicates that the mean LD of bacteria in Flush 1
through the ViaValve® catheter was statistically significantly smaller
than either the mean LD for the Autoguard™ BC (p-value = 0.0030) or
the mean LD for the Introcan® Safety 3 (p-value = 0.014).
Count
3.0
2.5
2.0
0.96
1.5
0.73
1.0
0.34
0.5
Green indicates that the mean LD for Autoguard™ BC was not
statistically significantly different than the mean LD for the Introcan®
Safety 3 (p-value = 0.17).
0.0
ViaValve®
Autoguard™ BC
Product
Introcan® Safety 3
Figure 5. Comparison of surface area (in2) and biofilm
count (CFU)
Figure 2. Incubation of inoculated catheters
The existing needleless connectors were then replaced with new
sterile connectors and unattached (planktonic) bacteria were rinsed
from the fluid path using sterile Phosphate Buffered Saline (PBS).
The catheters were then either sampled or subjected to simulated
clinical use by flushing 17 times daily with 0.5 ml sterile nutrient and
1 flush at the end of the day with normal saline for 72 and 96 hours.
The catheters were sampled with a two-step procedure. First, each
catheter was flushed to recover planktonic bacteria and plated to
determine CFU/ml (Flush 1). The connector surface was disinfected,
sonicated in PBS to remove firmly attached (biofilm) sessile
bacteria, and flushed a second time and plated (Flush 2).
Table 2. Yellow indicates that the mean LD of bacteria in Flush 2
through the ViaValve® catheter was statistically significantly smaller
than either the mean LD for the Autoguard™ BC (p-value < 0.0005) or
the mean LD for the Introcan® Safety 3 (p-value = 0.010).
Green indicates that the mean LD for the Autoguard™ BC was not
statistically significantly different than the mean for the Introcan®
Safety 3 (difference in means was 0.605 , p-value = 0.553).
Internal Volume and Surface Area in Contact with Blood
ViaValve® Autoguard™BC % difference
Internal volume (in3) 0.0038
0.0082
116%
(2.2 x more volume)
Internal surface area (in2) 0.34
0.73
114%
(2.1 x more SA)
ViaValve® Introcan® 3
Internal volume (in3)
0.0038
Internal surface area (in2) 0.34
Figure 3. Flushing catheters for clinical simulated
use and for planktonic and biofilm bacteria counts
% difference
0.017
347%
(4.5 x more volume)
0.96
182%
(2.8 x more SA)
Table 3. Comparison of the internal volume and surface area of the
Autoguard™ BC and the Introcan Safety® 3 catheter hubs to ViaValve®
Figure 6. Scanning electron microscope image of a component of a
blood valve within the flow path. The large aggregates of spherical
objects Indicate biofilm formation by Staphylococcus aureus.
RESULTS (cont.)
• There were statistically significantly smaller bacterial mean log
densities in Flush 1 and Flush 2 for ViaValve® compared to either
the Autoguard™ BC (p-value = 0.003 and 0.001 respectively) or
Introcan® Safety 3 catheters (p-value = 0.014 and 0.010
respectively).
• There were no differences in the bacterial mean log densities
between the Autoguard™ BC or the Introcan® Safety 3 in either
Flush 1 or Flush 2 (p-value = 0.17 and 0.55 respectively).
• ViaValve® Safety I.V. Catheters had fewer bacteria on internal
surfaces as well as a smaller internal surface area and less complex
fluid path.
• ViaValve® Safety I.V. Catheters had a statistically significant lower
bacterial transfer rate as well as the lowest surface area and biofilm
bacteria CFU counts which may minimize the risk of bloodstream
infection.