From CJIC Today: Further Validation of VP4 as New Standard!! I have simply copies much of the excellent paper published today in the peer reviewd Canadian Journal of Infection Control by Dufresne, Richards, and Molloy-Simard. This landmark paper demonstrates not only a gold standard TSO3 new technique for innoculating and demonstrating sterilization in long flexible scope lumens (using a Pentax colonoscope) that is unique in the industry in meeting FDA standards and goals, this study validates again the efficicacy and efficiency of the VP4 for sterilizing these four (multi) channel scopes! Note that the VP4 was even effective at sterilizing these colonoscopes with only a 1/2 cycle, as well as, of course, with a full cycle. The VP4 is the only low temperature sterilizer validated and approved for these complex scopes by the FDA. THE VP4 IS THE NEW STANDARD OF CARE IN LOW TEMPERATURE STERILIZATION!!
A new method to sterilize multichannel flexible
colonoscopes
Sylvie Dufresne, PhD,1 Thomas Richards, PhD, JD,2 Vanessa Molloy-Simard, MSc1 [Corresponding Author]
1 TSO3, Inc., 2505, avenue Dalton, Qubec (Qubec) G1P 3S5, Canada, 418-254-3008, sdufresne@tso3.com
2 IM3, Inc., 7720 NE Hwy 99, Suite D #110, Vancouver, Washington, USA, 503-415-0250, tomami20x@gmail.com
ABSTRACT
Background: Flexible gastrointestinal (GI) endoscopes have been associated with patient-to-patient transfer of multidrug-resistant bacteria that are not inactivated by
high-level disinfection. This has resulted in calls to reprocess GI endoscopes by sterilization. However, traditional low-temperature sterilization methods are not cleared
by the United States FDA to terminally sterilize complex multichannel endoscopes.
Aim: Demonstrate that the STERIZONE® VP4 Sterilizer (VP4 Sterilizer) can sterilize a multichannel colonoscope using a new gravity-based inoculation method.
Methods: In accordance with US, EU and Canadian requirements, a direct-inoculation method was developed to demonstrate that the VP4 Sterilizer can sterilize a
multichannel colonoscope under both half-cycle and simulated-use conditions.
Findings: Half-cycle and simulated-use testing demonstrated that the VP4 Sterilizer can sterilize a multichannel colonoscope with a sterility assurance level of SAL-6.
Validation of the inoculation method using surrogate lumens, confirmed that the center of each lumen contained >106 test organisms. Furthermore, both high and
low-level recovery was achieved for each lumen within a multichannel colonoscope.
Conclusion: Flexible colonoscopes can be terminally sterilized using the VP4 Sterilizer. It is the first vapor-based sterilization technology that is FDA cleared to sterilize a
four-channel flexible colonoscope.
KEY WORDS
colonoscope, sterilization
EMERGING TECHNOLOGIES
Canadian Journal of Infection Control | Fall 2017 | Volume 32 | Issue 3 | 165-171
INTRODUCTION
In accordance with the Spaulding Classification scheme, flexible
GI endoscopes including colonoscopes and gastroscopes have
been traditionally classified as semi-critical devices, meaning
that they should be sterilized before use, or if this is not possible,
reprocessed using high-level disinfection (HLD) (1). Because
flexible endoscopes are temperature sensitive, HLD has been
the preferred reprocessing method, reflecting the inadequacy
of available low-temperature sterilization technologies. Recently
however, both regulatory agencies and the medical community
have recognized that GI endoscopes should be reclassified from
semi-critical to critical devices, which requires reprocessing by
sterilization and not HLD (2).
The desire to sterilize GI endoscopes is in large part
caused by recent publicity involving patient-to-patient
transfer of multidrug-resistant organisms (MDROs) attributed
to endoscopes, particularly duodenoscopes (3). Although
some infectious outbreaks have been caused by breaches of
reprocessing (4), others have occurred even when endoscopes
have been reprocessed according to manufacturer’s instructionsfor-
use (IFU) (3). In particular, Ofstead et al, found that viable
microbes were identified on GI endoscopes reprocessed using
cleaning and disinfection methods provided by the device
manufacturer (5).
To address this problem, some device manufacturers have
begun to validate the use of ethylene oxide (EtO) as a method
for sterilizing GI scopes. However, EtO requires lengthy
aeration times and is associated with occupational health and
environmental risks. Also, EtO sterilizers are limited in the US to
sterilization of devices with a maximum of two lumens (6), which
by definition excludes modern GI endoscopes. Furthermore,
in studies published by Alfa et al involving inoculation and
sterilization of flexible surrogate lumens, data shows that EtO
efficacy is compromised when inoculum is mixed with inorganic
contaminants (7), which are intended to reflect “simulated-use”
conditions commonly found in a clinical setting.
Liquid chemical sterilization using peracetic acid is indicated
for reprocessing reusable critical and semi-critical heat-sensitive
medical devices including flexible endoscopes (8). As reported
by McDonnell et al (9), half-cycle testing using a peracetic-acid
system and commercial duodenoscopes, demonstrated a sterility
assurance level of SAL-6. However, reprocessed scopes must
be used at point-of-care, since the method does not allow for
terminal sterilization, which facilitates sterile storage.
Additionally, the effectiveness of first-generation vaporized
hydrogen peroxide (H2O2) sterilizers in sterilizing multi-lumen
devices has been evaluated and found inadequate to reprocess
a modern GI endoscope. Claim language varies by sterilizer
manufacturer, but at best is limited to only dual-channel flexible
scopes with the longest lumen 1 mm in Inner Diameter
(ID) and 1000 mm in length, which is well short of the
requirements for a modern colonoscope (10).
The process for validating sterilization claims for new device
designs is dictated by both international standards (11) and
regulatory guidance, such as provided by FDA (12). Specifically,
ISO 14937 requires that a sterilizer manufacturer demonstrate
that test devices, inoculated with at least 106 CFU of a highly
resistant organism, can be sterilized under half-cycle conditions.
Furthermore, the inoculation must provide the greatest
challenge to sterilant penetration, which for vapor-based
processes, is in the middle of a lumen.
In addition, FDA requires that test devices must pass
simulated-use testing, wherein the microbe suspension is mixed
with organic and inorganic soils and inoculated onto devices. For
a successful simulated-use validation, testing is to be performed in
triplicate with no growth observed following sterilization.
Because of the urgent need for a viable method to terminally
sterilize complex GI endoscopes, the effectiveness of a new
low-temperature dual-sterilant method was evaluated for
reprocessing a flexible video colonoscope. This in turn was
completed by use of a new validated test method for direct
inoculation of long-lumen multichannel flexible endoscopes.
METHODS
Sterilizer
The STERIZONE® VP4 Sterilizer (VP4 Sterilizer) (TSO3, Inc.,
Quebec Canada) was used in this study. A detailed description
of the device has been previously published (13). The
device uses dual sterilants (vaporized H2O2 and ozone), in a
multiphase process. The device is intended for use in terminal
sterilization of cleaned, rinsed, and dried metal and non-metal
reusable medical devices. The VP4 Sterilizer uses only a single
sterilization cycle irrespective of load configuration, with a
maximum load limit of 34 kg (75 pounds).
Test organism
The most resistant microorganism to either hydrogen peroxide
or ozone sterilants is Geobacillus stearothermophilus spores (14).
Spore suspensions of G. stearothermophilus ATCC 7953 (Lot
AR-469; population 2,2 ~ 108 colony forming unit (CFU)/mL)
were purchased from iuvo BioScience (Rush, NY). The spore
suspension populations were verified and adjusted to achieve
a final concentration of 1,0-2,5 ~ 106 CFU/10 μL, which was
used for validation of high-level recovery, as well as half-cycle
and simulated-use testing (the latter in combination with 400
ppm AOAC hard water and 5% fetal bovine serum).
The spore suspension was further diluted to 10-100 CFU/10
μL for validation of low-level recovery.
Lumen devices or surrogates
For the purpose of validating expanded sterilization claims, a
Pentax Video Colonoscope Model EC-3890Li (Pentax Medical,
Tokyo, Japan) was used. The manufacturer identifies seven
discrete lumens, consisting of four “channels” (Instrument, Air,
Water, and Forward Water Jet, extending from the distal end
of the device to the handle) and three “tubes” or umbilical
lumens (Suction, Air Feeding, and Water Feeding, extending
from the handle to the suction source, air pump, and water
bottle, respectively; see Figure 1). Channel dimensions,
which are the basis for FDA labeling claims for the VP4
Sterilizer, are 1,45 mm ID and 3 500 mm in length, and/
or 1,2 mm ID and 1 955 mm in length. Tube dimensions,
are all 2,4 mm ID and 1 580 mm in length. Validation
studies were completed on all channels and tubes (seven
in total) as defined by Dufresne (15), since all lumens can
become contaminated, although the device is commonly
referred to as a “four-channel” endoscope (consisting of air,
water, suction, and instrument channels).
Development and validation of the inoculation
method as well as high-level recovery method was
completed by use of surrogate fluoropolymers tubing
such as polytetrafluoroethylene (PTFE) or perfluoroalkoxy
alkanes (PFA) tubing, which are part of the same group
of fluoropolymers tubing used for commercial flexible
endoscopes. Tubing diameter and length was selected
to correspond to the dimensions found in the Pentax
colonoscope. Thus, surrogate PTFE tubing, ranging between
1 mm ID ~ 3 500 mm length, and 4 mm ID ~ 1 840 mm
length, were selected based on worst-case lumen dimensions
(smallest ID and longest length).
Inoculation and recovery method using surrogate lumens
PTFE lumens (three samples per dimension) were used to
develop the inoculation method for each lumen found in the
colonoscope, as well as to validate that a minimum of 106 spores
were deposited in the center of the lumen, as required by FDA.
Each lumen was temporarily placed on a vertical wall
such that the middle of the lumen was at the lowest height. A
minimum volume of sterile diluent solution (between 40-400
μL, depending on the lumen dimension) was added to 10
μL of inoculum (with and without hard water and serum) in
order that the collective volume would flow to the middle
of the test lumen. A micropipette with a low retention tip
was used to introduce the diluted inoculum into the lumen
orifice. Minimal visible droplets were observed on the sides of
the tube confirming that the inoculum was deposited in the
middle of the lumen. The objective was to use the smallest
diluent necessary in order to minimize drying time and to
ensure that inoculum was visibly collected in the center of the
test lumen. The inoculated tubes were left to dry.
After overnight drying of surrogate lumens, verification
of the spore count deposited in the middle of the tube was
performed by cutting the middle part of the PTFE tube (about
10 % of its total length) and separating it from the remainder of
the tubing. This portion of the tubing underwent recovery with
a 100 mL buffer solution. A pour plate method using Trypticase
Soy Agar (TSA) was performed to evaluate the population. The
plates were incubated at 55-60°C for a minimum of 48 hours.
The acceptance criteria for a successful high-level validation
required recovery of > 106 spores.Inoculation of the Pentax Colonoscope
for half-cycle test and simulated use test
The channels and tubes of each colonoscope were inoculated
with 1,0-2,5 ~ 106 CFU/10 μL using a direct inoculation method
based on gravity. A volume of 10 μL of inoculum was diluted with
40-400 μL of sterile diluent solution, which was introduced into
each lumen orifice separately using a gel loading micropipette.
For simulated-use, the inoculum was mixed with hard water and
serum as described previously (Test Organism Section).
The endoscope was inoculated in two groups: Group 1
included only the Forward Water Jet Channel and Group 2
included all other channels and tubes (six lumens in Group 2).
The Forward Water Jet Channel had to be inoculated separately
due to its considerable length, extending from the distal end of
the scope to the umbilical (Figure 1).
Sterilization
The endoscope was placed in a stainless steel basket and
packaged in a full length SteriTite® Container (Case Medical Inc,
South Hackensack, NJ). The container was placed on the lower
shelf of the sterilizer loading rack.
The load conditions used for the half-cycle and
simulated-use validation testing were selected to represent
the worst case conditions for sterile efficacy testing. The
recommended load temperature to be processed in the
STERIZONE® VP4 Sterilizer is 20°C to 26°C. Thus the
validation loads were pre-conditioned at 26°C prior to
being processed in the sterilizer. The pre-conditioning
temperature of 26°C was chosen, due to the fact that this
load condition requires the shortest sterilant exposure time
and results in the lowest mass of sterilant, and therefore
represent the most challenging condition for achieving
sterilization efficacy.
For the half-cycle test, the load was exposed to the first
phase of the process only. For simulated-use, the load was as
exposed to the complete Cycle (two sterilization pulses and
full aeration).
Tests were performed in triplicate for each inoculation
group under worst-case conditions. Prior to each test,
the colonoscope was reprocessed in accordance with the
manufacturer’s instructions before initiation of the next test,
which included cleaning, drying, and storage.Recovery
Recovery of viable spores was achieved by using a 60 mL syringe
and the cleaning connector provided by Pentax, following the
cleaning method described in the scope-reprocessing manual.
Three luer-lock connectors are available on the colonoscope,
with two of the three connectors associated with more than one
channel, and the Forward Water Jet having its own connector
(Figure 1). Thus, recovery buffer was passed through more than
one channel/tube (with the exception of the Forward Water Jet)
using syringes filled with recovery buffer.
The amount of recovery buffer used per channel/tube or
group of lumens was 100x the combined internal volume for
each lumen or group of lumens. Recovered buffer solution was
filtered using a 0,45 μm filter and placed on a TSA plate. Plates
were incubated at 55°-60°C for a minimum of 48 hours.
Controls: High level recovery
For high level recovery, each lumen of the Pentax endoscope was
tested individually. Each channel was inoculated as described for
the half-cycle and simulated use tests. After drying overnight,
recovery was performed. A pour plate method using TSA was
performed to evaluate the population after heat shock (95-
100°C for 15 min) (16). The plates were incubated at 55-60°C
for a minimum of 48 hours. A successful high-level validation
required recovery of > 106 spores.
Controls: Low level recovery
In order to confirm low-level recovery, the standard spore
suspension was diluted to 10-100 CFU/10 μL. Each channel
was inoculated as described for the half-cycle test, but using
10-100 CFU/10 μL spore suspension. After drying overnight,
recovery was performed. Recovered buffer solution was
filtered using a 0,45 μm filter and placed on a TSA plate.
Plates were incubated at 55°-60°C for a minimum of
48 hours. The recovery percentage was calculated using
the count of the inoculating spore suspension as 100%.
A successful low-level validation required recovery of a
minimum of 25% spores.
RESULTS
Half-cycle and simulated-use testing of video colonoscope
No viable microorganisms were recovered from any of the
inoculated challenges subsquent to exposure to either half-cycle or
simulated-use testing conditions (Table 1), despite the fact that six
inoculated lumens (within Group 2) were sterilized simultaneously.
Controls – verification of inoculum in the center of test lumens
All lumens were inoculated with a spore suspension of 1,71 ~
106 CFU/10μL (spore alone) or between 1,02 and 1,53 ~ 106
CFU/10μL when spores were mixed with 5% serum and 400 ppm
hard water. High-level recovery using PTFE lumens confirmed that
a population of at least 106 spores was recovered from the middle
of all test lumens, irrespective of ID or length. This was true if the
suspension was used either alone (78-92% recovery) or if combined
with serum and hard water (74-80% recovery – See Table 2).
Controls: High level recovery
The population of the spore suspension used for high level
recovery was 1,71 ~ 106 CFU/10μL (spores alone) or between
1,02 and 1,53 ~ 106 CFU/10μL for spores mixed with 5%
serum and 400 ppm hard water. High-level recovery for
each inoculated channel and tube within the colonoscope
also confirmed a population of at least 106 spores. This was
confirmed when the suspension was used alone (77-95%
recovery by lumen) or with serum and hard water (91-105%
recovery by lumen – See Table 3).
Controls: Low level recovery
The population of the spore suspension used for low level recovery
was determined to be between 69-90 CFU/10μL; low-level
recovery was not done with spores mixed with serum and hard
water. Low-level recovery was lower than with high-level recovery,
but was judged to be satisfactory, particularly considering the long
lengths and complicated access found with the test endoscope
(range 29-67 % recovery by lumen – See Table 4).
DISCUSSION
In 2015, the STERIZONE® VP4 Sterilizer was approved
by Health Canada and the EU to include sterilization of
multichannel flexible GI endoscopes including colonoscopes
and gastroscopes. It was subsequently cleared by FDA in June
2016 to include sterilization of flexible endoscopes with lumens
1,45 mm ID and 3 500 mm in length (and/or 1,2 mm ID
and 1 955 mm in length). To date, the VP4 Sterilizer is the
only vapor-based sterilizer to receive FDA clearance to sterilize a
four-channel flexible GI endoscope.
Numerous methods have been published on how to
inoculate and recover test organisms from lumens for use in
sterilization validation studies. However, in general the methods
have been validated for only simple lumen devices, and do
not reflect multiple, long lumens as found in a GI endoscope.
Furthermore, many of the methods require use of a surrogate
lumen and not actual endoscopes, as mandated by FDA.
For example, Okpara-Hofmann et al described the use of
either stainless steel squares or wire carriers, inoculated with
106 bacterial spores, and placed in the middle of an endoscope
biopsy channel (17). The longest endoscope evaluated had a
biopsy channel of 2,8 mm ID and was only 1 160 mm long. The
author’s counseled against direct inoculation of the endoscope
due to low colony counts in recovery, caused by the spore
suspension being lost in “niches and lumens.”
Diab-Elschahawi et al also described use of an inoculated
wire carrier placed in the midpoint of a surrogate stainless steel
lumen measuring 0,7 mm ~ 500 mm18. Although the carrier
was significantly longer than used by Okpara-Hofmann, the
carrier was not qualified for use in long flexible lumens.
Dufresne et al tested surrogate lumens made of stainless steel
tubing with diameters ranging between 0,5-4,0 mm, and lengths
ranging between 450-700 mm (19). For the smallest diameter
lumens, tubing was directly inoculated with spore suspension.
For all other tubing, the microbial challenge was created by
placing an inoculated wire inside the channel, which was longer
than the lumen to be sterilized.
Finally, McDonnell et al reported the direct inoculation
of a four-channel duodenoscope by flushing 0,5 mL spore
suspension (with a titer of 108 CFU/mL) through the port and
through each channel of the device (9). Satisfactory high and
low-level validation was reported. Nonetheless, the method
would not satisfy FDA requirements for validation of a vaporbased
sterilization process, which requires confirmation that the
inoculum is deposited into the middle of each channel.
Due to the complexity of modern GI endoscopes, and
FDA’s specific requirements for the location of inoculum and
validation of spore recovery, neither carriers nor conventional
direct inoculation methods are satisfactory. In particular, carriers
are difficult to insert into endoscope lumens due to valves and
other restrictions, which are not found in surrogate lumens. In
addition, spores may be lost due to the interaction of the carrier
with lumen walls during insertion. Therefore, a new validated
test method was required for direct inoculation of long-lumen
multichannel flexible endoscopes. The gravity-based inoculation
method described herein satisfied FDA requirements for
targeted inoculation and recovery efficacy.
Application of the direct inoculation method confirmed that
the VP4 Sterilizer achieves a six log spore reduction in each of
seven colonoscope lumens under half-cycle and simulated-use
conditions. This represents the first sterilization validation of a
modern multichannel GI endoscope using a vapor-based sterilant.
The development of sterilization methods for long-lumen
devices is an important advancement. It is reported that more
than 10 million GI endoscopic procedures are performed every
year in the US, which equates to a significant risk of patientto-
patient transfer of MDROs (2). However, sterilization does
not necessarily compensate for inadequate or timely cleaning
of the endoscope immediately following a procedure. Thus,
successful reprocessing of a complex endoscope must be viewed
in the context of thorough bedside cleaning, manual cleaning,
automated endoscope reprocessing, and terminal sterilization.
CONCLUSIONS
A new gravity based inoculation method using sterile diluent
demonstrated that spores were consistently deposited in the
center of each test lumen as required by FDA for sterilization
validation studies. Furthermore, both high and low-level
recovery confirmed that spores could be recovered from
inoculated lumens. Application of the method to half-cycle
and simulated-use testing with a multichannel colonoscope
was confirmed, verifying that complex GI scopes can be
terminally sterilized using the STERIZONE® VP4 Sterilizer. The
FDA’s clearance of this device for the terminal sterilization of
multichannel video colonoscopes is a milestone in reducing risk
for patients using these critical medical devices.
(I WILL ASK SOMEONE WITH DROPBOX TO POST THE ENTIRE ARTICLE, WITH TABLES AND FIGURES. THANKS SO MUCH!)