U.S. patent application number 11/679208 was filed with the patent office on 2008-08-28 for biological indicator for use with vaporous microbial deactivating agents and method for making same.
This patent application is currently assigned to STERIS Inc.. Invention is credited to Anthony W. Dallmier, Christopher W. Fisher, Timothy J. Millett.
Application Number | 20080206801 11/679208 |
Document ID | / |
Family ID | 39716327 |
Filed Date | 2008-08-28 |
United States Patent
Application |
20080206801 |
Kind Code |
A1 |
Dallmier; Anthony W. ; et
al. |
August 28, 2008 |
BIOLOGICAL INDICATOR FOR USE WITH VAPOROUS MICROBIAL DEACTIVATING
AGENTS AND METHOD FOR MAKING SAME
Abstract
A biological indicator and method of making same. The biological
indicator includes a carrier having a recess formed therein in
order to restrict movement of an inoculum deposited onto the
carrier. The inoculum includes microorganisms (e.g., bacterial
spores) suspended in a suspension medium. The microorganisms are
prepared by removing extraneous material and subjecting the
microorganisms to sonication to break up agglomerations. The
suspension medium includes a wetting agent to reduce surface
tension, thereby facilitating flow of the suspension medium to
prevent stacking of microorganisms on the surface of the carrier,
and to allow the inoculum to more evenly "plate out" on carrier
surfaces. The carrier, with inoculum deposited thereon, is enclosed
in an envelope made of a material permeable to a vaporous
deactivating agent (e.g., vaporized hydrogen peroxide, ozone,
chlorine dioxide, ethylene oxide, etc.), thereby facilitating
exposure to the vaporous deactivating agent.
Inventors: |
Dallmier; Anthony W.;
(Concord, OH) ; Fisher; Christopher W.;
(Mentor-on-the-Lake, OH) ; Millett; Timothy J.;
(Mentor, OH) |
Correspondence
Address: |
KUSNER & JAFFE;HIGHLAND PLACE SUITE 310
6151 WILSON MILLS ROAD
HIGHLAND HEIGHTS
OH
44143
US
|
Assignee: |
STERIS Inc.
|
Family ID: |
39716327 |
Appl. No.: |
11/679208 |
Filed: |
February 27, 2007 |
Current U.S.
Class: |
435/29 |
Current CPC
Class: |
C12M 37/06 20130101;
C12Q 1/02 20130101 |
Class at
Publication: |
435/29 |
International
Class: |
C12Q 1/02 20060101
C12Q001/02 |
Claims
1. A biological indicator for determining the efficacy of a
microbial deactivation process used to deactivate items by exposing
said items to a vaporous deactivating agent, said biological
indicator comprising: a carrier having a recess formed therein; and
an inoculum including microorganisms suspended in a suspension
medium, wherein the inoculum is deposited in the recess.
2. A biological indicator as defined in claim 1, wherein said
recess is defined by a bottom surface and sloping side walls that
surround the bottom surface and slope away therefrom.
3. A biological indicator as defined in claim 1, wherein said
microorganisms include at least one of the following: bacterial
spores, bacteria, fungi, viruses, or a combination thereof.
4. A biological indicator as defined in claim 1, wherein said
biological indicator further comprises an envelope for enclosing
said carrier having said inoculum deposited thereon.
5. A biological indicator as defined in claim 4, wherein said
envelope is formed of a material that is permeable to said vaporous
deactivating agent and generally impermeable to said
microorganisms.
6. A biological indicator as defined in claim 5, wherein said
material comprises spun-bonded olefin.
7. A biological indicator as defined in claim 1, wherein said
suspension medium includes a wetting agent.
8. A biological indicator as defined in claim 7, wherein said
wetting agent is a surfactant compatible with said vaporous
deactivating agent.
9. A biological indicator as defined in claim 1, wherein said
suspension medium includes an alcohol.
10. A biological indicator as defined in claim 1, wherein said
carrier is formed of a polymeric material.
11. A biological indicator as defined in claim 10, wherein said
polymeric material includes at least one of the following:
polypropylene, polyethylene, polyvinyl-carbonate, polyvinyl
styrene, polyvinyl chlorine, polyethylene terephtlialate, nylon,
epoxy, or a mixture of polymeric materials.
12. A biological indicator as defined in claim 1, wherein said
carrier is formed of a metal.
13. A biological indicator as defined in claim 12, wherein said
carrier includes at least one of: aluminum or stainless steel.
14. A biological indicator as defined in claim 1, wherein said
carrier is formed of a ceramic.
15. A biological indicator as defined in claim 1, wherein said
vaporous deactivating agent is vaporized hydrogen peroxide.
16. A method of making a biological indicator comprised of a
carrier and an inoculum including microorganisms suspended in a
suspension medium, the biological indicator determining the
efficacy of a deactivation process used to deactivate articles by
exposing said articles to a vaporous deactivating agent, said
method comprising the steps of: cleaning the carrier using a
cleaning agent including a detergent; removing extraneous material
from said microorganisms; exposing said microorganisms to
ultrasonic vibrations to break up agglomerations of said
microorganisms; suspending said microorganisms in the suspension
medium to form the inoculum; and depositing said inoculum onto said
carrier.
17. A method of making a biological indicator as defined in claim
16, wherein said step of removing extraneous material from said
microorganisms includes washing said microorganisms.
18. A method of making a biological indicator as defined in claim
16, wherein said suspension medium includes a wetting agent.
19. A method of making a biological indicator as defined in claim
18, wherein said wetting agent is a surfactant compatible with said
vaporous deactivating agent.
20. A method of making a biological indicator as defined in claim
16, wherein said suspension medium includes an alcohol.
21. A method of making a biological indicator as defined in claim
16, wherein said method further comprises: enclosing said carrier
having inoculum deposited thereon in an envelope made of a material
permeable to said vaporous deactivating agent and generally
impermeable to said microorganisms.
22. A method of making a biological indicator as defined in claim
21, wherein said material includes a spun-bonded olefin.
23. A method of making a biological indicator as defined in claim
16, wherein said method further comprises the step of: rinsing said
carrier with a rinsing solution including an alcohol, prior to
depositing said inoculum thereon.
24. A method of making a biological indicator as defined in claim
16, wherein said microorganisms include at least one of the
following: bacterial spores, bacteria, fungi, viruses, or a
combination thereof.
25. A method of making a biological indicator as defined in claim
1, wherein said vaporous deactivating agent includes: vaporized
hydrogen peroxide, ozone, chlorine dioxide, or ethylene oxide.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a biological indicator for
determining the efficacy of a microbial deactivation process.
BACKGROUND OF THE INVENTION
[0002] Many articles (e.g., medical instruments and devices) and
enclosed regions of a wide range of facilities (e.g., medical
treatment and research facilities, pharmaceutical manufacturing
facilities, animal research facilities, laboratories, patient
rooms, hotel rooms, offices, cruise ships, recreational facilities
and vehicles) are treated with a vaporous deactivating agent (e.g.,
vaporized hydrogen peroxide) in a microbial deactivation process to
deactivate microbial contamination on the articles or contaminated
surfaces within the enclosed region. In order to determine whether
the treated articles or enclosed regions have been successfully
deactivated, and thereby safe for use, it is necessary to determine
whether all of the parameters necessary for deactivation were met
during the deactivation process or are present within the enclosed
region during the microbial deactivation process. To this end,
biological indicators accompany the articles, or are located within
the enclosed region, throughout the microbial deactivation process.
A typical biological indicator includes a known number of
microorganisms (usually bacterial spores) of known resistance to
the mode of deactivation, located in or on a carrier (also referred
to as a "coupon" or "strip"), and enclosed in a protective package.
Before the microorganisms are deposited onto the carrier, the
microorganisms are typically suspended in a suspension medium.
Subsequent growth or failure of the microorganisms to grow, i.e.,
after the deactivation process, under suitable conditions indicates
the efficacy of the microbial deactivation process.
[0003] Known biological indicators include a carrier formed of a
metal, such as stainless steel. The carrier has a uniform flat
surface on one side of the carrier, upon which microorganisms are
deposited. The carrier is typically enclosed within the protective
package having one side formed of a material permeable to a
vaporous deactivating agent (e.g., Tyvek.RTM.) and having the other
side formed of a material impermeable to the vaporous deactivating
agent (e.g., Mylar.RTM.). The carrier is oriented within the
package such that the side of the carrier having the microorganisms
thereon faces the permeable side of the package, while the opposite
side of the carrier faces the impermeable side of the package.
[0004] One problem with known biological indicators is that
microorganisms become "stacked" on the surface of the carrier,
thereby shielding some of the microorganisms from exposure to the
vaporous deactivating agent. FIG. 1 illustrates a prior art
biological indicator 70 comprised of a carrier 72 having
microorganisms 78 suspended within a suspension medium 76.
Suspension medium 76 is deposited onto the flat upper surface of
carrier 72. As shown in FIG. 1, microorganisms 78 are "stacked"
within suspension medium 76 due to suspension medium 76 failing to
more evenly distribute across the upper surface of carrier 72.
[0005] Still another problem encountered with known biological
indicators is that microorganisms disposed on the flat upper
surface of the carrier come into contact with the package enclosing
the carrier. As a result, microorganisms can be removed from the
carrier. Once removed from the carrier, microorganisms may migrate
to the opposite side of the carrier facing the impermeable
packaging. As a result, the microorganisms may be "masked" from the
deactivation process.
[0006] Yet another problem with known biological indicators is that
the carrier may shift positions within the protective package,
thereby causing the side of the carrier having microorganisms
deposited thereon to face the impermeable side of the protective
package. Accordingly, exposure of the microorganisms to the
vaporous deactivating agent is inhibited.
[0007] The problems described above result in a biological
indicator that does not accurately indicate the efficacy of a
microbial deactivation process.
[0008] The present invention overcomes these and other problems by
providing an improved biological indicator for determining the
efficacy of a microbial deactivation process using a vaporous
deactivating agent, and a method for making said biological
indicator.
SUMMARY OF THE INVENTION
[0009] In accordance with one aspect of the present invention,
there is provided a biological indicator for determining the
efficacy of a microbial deactivation process used to deactivate
items by exposing said items to a vaporous deactivating agent, said
biological indicator comprising: a carrier having a recess formed
therein; and an inoculum including microorganisms suspended in a
suspension medium, wherein the inoculum is deposited in the
recess.
[0010] In accordance with another aspect of the present invention,
there is provided a method of making a biological indicator
comprised of a carrier and an inoculum including microorganisms
suspended in a suspension medium, the biological indicator
determining the efficacy of a deactivation process used to
deactivate articles by exposing said articles to a vaporous
deactivating agent, said method comprising the steps of: (a)
cleaning the carrier using a cleaning agent including a detergent;
(b) removing extraneous material from said microorganisms; (c)
exposing said microorganisms to ultrasonic vibrations to break up
agglomerations of said microorganisms; (d) suspending said
microorganisms in the suspension medium to form the inoculum; and
(e) depositing said inoculum onto said carrier.
[0011] An advantage of the present invention is the provision of a
biological indicator having an inoculum with minimal extraneous
material therein.
[0012] Another advantage of the present invention is the provision
of a biological indicator having a suspension medium that minimizes
stacking of microorganisms.
[0013] Still another advantage of the present invention is the
provision of a biological indicator having a carrier dimensioned to
inhibit migration of inoculum.
[0014] Still another advantage of the present invention is the
provision of a biological indicator having a carrier formed of a
material compatible with an oxidative vaporous microbial
deactivating agent.
[0015] Still another advantage of the present invention is the
provision of a biological indicator having a protective packaging
with improved permeability for vaporous microbial deactivating
agents.
[0016] Yet another advantage of the present invention is the
provision of a method for making the above-mentioned biological
indicator.
[0017] Yet another advantage of the present invention is the
provision of a method of making a biological indicator that
minimizes agglomeration of microorganisms.
[0018] These and other advantages will become apparent from the
following description of a preferred embodiment taken together with
the accompanying drawings and the appended claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0019] The invention may take physical form in certain parts and
arrangement of parts, a preferred embodiment of which will be
described in detail in the specification and illustrated in the
accompanying drawings which form a part hereof, and wherein:
[0020] FIG. 1 is a perspective cutaway view of a carrier of a prior
art biological indicator;
[0021] FIG. 2 is a perspective cutaway view of a carrier for a
biological indicator according to an embodiment of the present
invention;
[0022] FIG. 3 is a cross-sectional view of a biological indicator
according to an embodiment of the present invention, said
biological indicator including a carrier, inoculum and
packaging.
DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT
[0023] It should be understood that as used herein the term
"vaporous" deactivating agents also includes "gaseous" deactivating
agents. By way of example, and not limitation, the deactivating
agents may include vaporized hydrogen peroxide, ozone, chlorine
dioxide, and ethylene oxide.
[0024] Referring now to the drawings wherein the showings are for
the purpose of illustrating a preferred embodiment of the invention
only, and not for the purpose of limiting same, FIG. 3 shows a
biological indicator (BI) 10 according to an embodiment of the
present invention. BI 10 is generally comprised of a carrier 20
(best seen in FIG. 2); an inoculum 30 comprised of a plurality of
microorganisms 38 suspended in a suspension medium 36; and an
envelope 46. Inoculum 30 is prepared by suspending microorganisms
38 within suspension medium 36. Inoculum 30 is deposited onto
carrier 20. Thereafter, carrier 20 is sealed within envelope 46.
Each component of BI 10 is described in detail below.
[0025] In the illustrated embodiment, carrier 20 is a generally
planar plate or strip having a cavity or recess 22 formed on one
side thereof, as best seen in FIG. 2. Recess 22 is defined by a
generally planar bottom surface 24 and a plurality of side walls 26
surrounding bottom surface 24. Side walls 26 slope upward from
bottom surface 24 to a generally planar upper surface 28 that is
disposed around the periphery of recess 22. Recess 22 is
dimensioned to receive inoculum 30, comprised of microorganisms 38
suspended in a suspension medium 36.
[0026] Carrier 20 is preferably formed of a polymeric material such
as polypropylene, polyethylene, polyvinyl-carbonate, polyvinyl
styrene, polyvinyl chlorine, polyethylene terephthalate, nylon,
epoxy, or a mixture of polymeric materials. It is also contemplated
that carrier 20 may be formed of a metal (such as aluminum or
stainless steel) or a ceramic. However, carrier 20 is preferably
formed of a polymeric material since polymeric materials do not
oxidize in the presence of oxidizing vaporous microbial
deactivating agents, such as vaporized hydrogen peroxide; provide
flexibility to allow a wide variety of shapes for carrier 20; and
are relatively inexpensive.
[0027] In a preferred embodiment, suspension medium 36 of inoculum
30 is an aqueous solution comprising an oxidant-compatible
surfactant. Suitable surfactants include, but are not limited to,
Triton.RTM. X-100, Tween.RTM. 80 or sodium dodecyl sulfate. The
surfactant acts as a wetting agent to reduce surface tension,
thereby reducing microorganism "stacking." Suspension medium 36 may
also include an alcohol to increase the rate at which suspension
medium 36 dries after being deposited into recess 22 of carrier 20.
Suitable alcohols include, but are not limited to, ethyl alcohol or
iso-propyl alcohol. Reduced surface tension and faster drying
allows suspension medium 36, and microorganisms 38 suspended
therein, to more easily and readily spread across bottom surface 24
of carrier 20. Increased spreading of inoculum 30 minimizes
"stacking" of microorganisms 3 8 within suspension medium 36.
[0028] In the illustrated embodiment, microorganisms 38 of inoculum
30 are bacterial spores, including, but not limited to, the
following: Geobacillus stearothermophilus, Bacillus atrophaeus, B.
pumilus, C. sporogenes, and combinations thereof. It should be
understood that microorganisms 38 are not limited to bacterial
spores, and thus may include bacteria (such as Staphylococcus
aureus, Salmonella choleraesuis and Pseudomonas aeruginosa), fungi
(such as Tricophyton mentagrophytes), and viruses.
[0029] In the illustrated embodiment, envelope 46 is comprised of
two generally flexible, planar sheets 48a and 48b. Sheets 48a, 48b
are attached to each other along their perimeters (e.g., by an
adhesive or by heat sealing). Envelope 46, formed by sheets 48a and
48b, is dimensioned to enclose carrier 20. In the illustrated
embodiment sheets 48a, 48b are both formed of a material permeable
to vaporous deactivating agents, such as vaporized hydrogen
peroxide, but generally impermeable to microorganisms, such as
bacterial spores. Preferably, sheets 48a, 48b are formed of a
nonwoven polymer material, such as an olefin that is spun-bonded. A
suitable spun-bonded olefin material is commercially available from
Dow Chemical as Tyvek.RTM.. In one embodiment of the present
invention, sheets 48a, 48b are formed of 2FS Tyvek.RTM.. By way of
example and not limitation, sheets 48a, 48b may also be formed of
one of the following materials: 1073B Tyvek.RTM., other Tyvek.RTM.
products, non-woven polymers, olefins, polyester film, and a
combination thereof. However, 2FS Tyvek.RTM. is a preferred
material due to its permeability with respect to vaporous
deactivating agents.
[0030] Preparation of the surfaces of carrier 20 in advance of
depositing inoculum 30 thereon will now be described. Carrier 20 is
prepared as follows: during a cleaning step, carrier 20 is exposed
to a cleaning agent for a predetermined period of time. Preferably,
the cleaning agent includes an enzymatic detergent, such as STERIS
Klenzyme.RTM. detergent, available from STERIS Corporation of
Mentor, Ohio. The purpose of the cleaning step is to remove oils
(e.g., casting oils), organics, dirt and other contaminants from
the surface of carrier 20, thereby reducing oxidant demand during a
microbial deactivating process. In this regard, contaminants, such
as oil, can be oxidized by a vaporous decontaminating agent (e.g.,
vaporized hydrogen peroxide), thus reducing the amount of vaporous
deactivating agent acting upon the target microorganisms 38.
[0031] Following the cleaning step, carrier 20 is exposed to a
rinsing fluid for removal of any residual materials remaining on
the surfaces of carrier 20, such as residual cleaning agent. In one
embodiment, the rinsing fluid includes an alcohol such as ethyl or
isopropyl alcohol.
[0032] Prior to suspension within suspension medium 36,
microorganisms 38 undergo a "washing" procedure to remove
extraneous material therefrom. By way of example, but not
limitation, the extraneous material may include cellular debris,
excess organic material, growth media, and "spent" microorganisms
38. Removal of extraneous material from microorganisms 38 also
reduces oxidant demand during a microbial deactivating process. As
a result, a greater amount of the vaporous deactivating agent can
act upon the target microorganisms 38. It should be understood that
dyes are preferably omitted from suspension medium 36 to reduce
oxidative demand during a microbial deactivating process, since
dyes are also inherently prone to oxidative attack.
[0033] As indicated above, removing contaminants from the surfaces
of carrier 20, removing extraneous materials from microorganisms 38
prior to deposition onto carrier 20, and eliminating dyes from
suspension medium 36, minimizes the oxidative demand from materials
other than microorganisms 38. Accordingly, a greater amount of the
oxidative vaporous deactivating agent is available to act on
microorganisms 38 within suspension medium 36. As a result, the
accuracy of BI 10 is improved.
[0034] Prior to suspension within suspension medium 36,
microorganisms 38 also undergo a "mild" sonication (e.g.,
ultrasonic vibrations) to minimize agglomeration (i.e., "clumping")
of microorganism 38. Reduction of agglomeration improves the
ability of microorganisms 38 to flow or spread across bottom
surface 24 of carrier 20 when inoculum 30 is deposited in recess
22.
[0035] After suspension medium 38 and microorganisms 36 have been
prepared as described above, inoculum 30 is formed by suspending
microorganisms 36 in suspension medium 38.
[0036] Following preparation of inoculum 30 and carrier 20, as
described above, inoculum 30 is deposited into recess 22 of carrier
20. Inoculum 30 spreads out across bottom surface 24 due to the
reduced surface tension provided by the surfactant. Side walls 26
maintain inoculum 30 within recess 22, thereby preventing migration
of inoculum 30 onto upper surface 28. Side walls 26 also prevent
inoculum 30 from becoming removed from carrier 20 or from migrating
onto the inner surfaces of envelope 46. In addition, side walls 26
minimize "drop formation" by causing inoculum 30 to plate out on
side walls 26. Recess 22 allows faster production of BI 10, since
migration of inoculum 30 is inhibited.
[0037] As indicated above, the reduced surface tension of
suspension medium 36 facilitates the spreading of inoculum 30
across the area of bottom surface 24. As a result, microorganisms
38 are spread across a larger surface area than with prior art BI
70, thereby minimizing stacking of microorganisms 38. Less stacking
of microorganisms 38 results in improved exposure of microorganisms
38 to the vaporous deactivating agent. In this regard, when
microorganisms 38 are stacked (see FIG. 1), microorganisms 38
located at the top of the stack block microorganisms 38 located
below. The blocked microorganisms 38 thus fail to be properly
exposed to the vaporous deactivating agent. As a result, the
accuracy of the biological indicator can be impaired.
[0038] The presence of the alcohol in suspension medium 36 allows
for fast drying of inoculum 30 after deposition into recess 22,
thereby minimizing opportunities for unwanted migration of inoculum
30 during handling of BI 10. The presence of alcohol also reduces
surface tension, thereby providing the advantages described
above.
[0039] After inoculum 30 has dried on bottom surface 24 of carrier
20, carrier 20 is sealed inside envelope 46. As indicated above,
sheets 48a, 48b are preferably formed of a material permeable to
the vaporous deactivating agent (e.g., vaporized hydrogen
peroxide), but impermeable to microorganisms 38.
[0040] Operation of BI 10 will now be described with reference to
the deactivation of articles within a deactivation chamber. BI 10
is placed within the deactivation chamber along with articles that
are to be subject to a microbial deactivation process. The articles
and BI 10 are exposed to a vaporous deactivating agent (such as
vaporized hydrogen peroxide) during the microbial deactivation
process.
[0041] After the microbial deactivation process is completed,
biological indicator 10 is removed from the deactivation chamber
and microorganisms 36 are cultured to determine whether any of
microorganisms 36 remain viable following the microbial
deactivation process. If less than a threshold number of
microorganisms 36 remain viable following exposure to the vaporous
deactivating agent during the microbial deactivation process, then
the microbial deactivation process is considered to have been
effective.
[0042] The foregoing is one embodiment of the present invention. It
should be appreciated that this embodiment is described for
purposes of illustration only, and that those skilled in the art
may practice numerous alterations and modifications without
departing from the spirit and scope of the invention. It is
intended that all such modifications and alterations be included
insofar as they come within the scope of the invention as claimed
or the equivalents thereof.
* * * * *