Disinfection and Sterilization in the
Healthcare Environment
Richard A. Van Enk, Ph.D., CIC
Director, Infection Prevention and Epidemiology,
Bronson Methodist Hospital
vanenkr@bronsonhg.org
1
Objectives
You will be able to:
1. Know the terminology and definitions
related to disinfection and sterilization
2. Differentiate the various methods used for
disinfection and sterilization, with their
advantages and disadvantages
3. Review and monitor the disinfection and
sterilization processes in your facility
4. Recognize some recent challenges related to
disinfection
2
Introduction
• This session will discuss the process by which we
make invasive procedures safer by eliminating
microorganisms on the devices used in the
procedures
• Contaminated medical devices can cause
infections
• Endoscopy procedures are the highest risk
• Because of some highly-publicized situations,
regulators are looking at this process very closely
and we have to work very hard to make it safer
3
Terminology of microbial control
• Sterilization
– Destruction of all forms of microbial life
– Prions are a special case
– Examples of sterilants; autoclave and incineration
• Disinfection
– Destruction of disease-causing microorganisms
– Examples of disinfectants; bleach, “quats”
• Antisepsis
– Disinfection safe for use on human tissues
– Examples of antiseptics; iodine, alcohol, peroxide
4
Terminology of microbial control
• Sanitize
– Microbial control to public health standards
– Sanitizers prevents epidemics, mainly foodborne and
other gastrointestinal infections
– Used in bathroom and kitchen environments
• Decontaminate
– Make safe to handle
• “-cide” denotes killing
• “-stat” denotes inhibition
5
Factors affecting microbial killing
• Microbial Factors
– Microorganisms vary in susceptibility to killing and
are ranked in six or seven groups
– Antimicrobial agents are graded by the EPA
according to the microbial rank they can kill
– Log-phase bacteria are most susceptible to killing,
stationary are most resistant
• Environmental Factors
– Temperature, pH, and presence of organic matter
protecting the microorganisms
6
Ranking of microorganisms in resistance to
killing
↓ Critical devices, requires sterilization
• Bacterial endospores (Bacillus, Clostridium)
↓ Semi-critical devices, requires high level disinfection
• Fungal spores
↓
↓ Non-critical devices, intermediate level disinfection
• Mycobacteria (M. tuberculosis) note; tuberculocidal
• Naked (non-lipid coated) viruses
↓ Non-critical devices, low-level disinfection
• Fungi
• Bacteria
• Lipid-coated viruses
7
8
Kinetics of microbial death
• Like microbial growth, the rate of microbial death
under constant conditions is constant and
logarithmic and takes time
• Expressed as the decimal reduction time (D)
– The time needed to kill 90% of the population
– Example: If D is one minute, it takes one minute to go
from 1000 cells to 100, two minutes to go to 10, three
minutes to go to 1, four minutes to (theoretically) kill
them all
• The fewer the microorganisms you start with, the
shorter the time it takes to kill them
9
10
Microbial killing by heat
• Different forms of heat are used for different
applications
• Dry heat oxidizes (burns) the cell components
• Heat with moisture hydrolyzes chemical bonds
• Hydrolysis kills much faster than oxidation
• Positive features of heat;
– Effective, fast, easy, reliable, cheap, non-toxic
• Negative features of heat;
– Heat or moisture may damage some products
(paper, plastic, organic chemicals)
11
Conventional autoclave
• Sterilizes (kills
endospores)
• Uses steam under
pressure
• Uses 121°C at 15
pounds per square
inch (psi) for 15
minutes
• For items that can get
wet
• Items are wrapped in
paper and placed in
metal caskets to
protect them
12
The autoclave; flash sterilization
• When an instrument in the
OR needs to be re-sterilized
quickly and you don’t have
time to take it through the
whole reprocessing process
– Dropped on the floor
– Needed for the next case
• The item can be sterilized in a
little autoclave in the OR and
used immediately
• High risk; not inspected, used
wet, no QC
• Regulators do not like it at all
13
Gas sterilizers
• Ethylene oxide gas
– Steris Isomedix, 3M Steri-vac
– Denatures proteins and DNA
– Used for some heatsensitive hospital
instruments
– Explosive, toxic, slow
• H2O2 Plasma sterilizers
– Sterrad®, others
– Generates superoxide
radicals in vapor form
– Can replace autoclaves in
some applications, not
others
14
Pasteurization
• First discovered by Louis Pasteur
• A disinfectant process often used on medical devices
for high level disinfection (not sterilization)
–
–
–
–
Endoscopes that go into the respiratory, genital or GI tract
Respiratory care parts
Anesthesia equipment
Vaginal probes
• Uses combinations of heat and moisture to kill
microorganisms
– Usually about 70° C for 30 minutes
• Item becomes safe but not sterile
15
Chemical disinfectants/sterilants
• Registered by the EPA (disinfectants) and FDA (sterilants)
• We use the Spaulding system (Earle H. Spaulding) of critical,
semi-critical and non-critical disinfection in hospitals
– Sterilants produce sterility, for critical items
– High-level disinfectants kill all pathogens, for semi-critical
– Intermediate-level disinfectants kill mycobacteria and below on the
killing scale
– Low-level disinfectants kill less resistant microorganisms, for noncritical items
– The same chemical can be used as a sterilant or high-level
disinfectant depending on the time of exposure or strength
• Must be used according to directions
– Sensitive to temperature, pH, dilution, diluent, time, organic
background
16
Chemical disinfectant classes
• Alcohols (ethanol and isopropanol)
–
–
–
–
Antiseptics
Dissolves lipids, disrupts membranes, proteins
Usually used as a 70% concentration in water
Example; hand sanitizer, wiping skin before an injection
• Halogens (iodine and chlorine)
– Oxidize proteins
– Iodine as tincture (with alcohol) or iodophor (a chemical that
controls the release of the halogen)
– Chlorine as 0.5 ppm in water (bleach)
– Example; Betadine
17
Chemical disinfectant classes
• Phenol and Phenolics
– Damages plasma membranes
– Has residual activity on surfaces
– Powerful, long-acting, but can damage some materials;
was used in operating rooms, not used in hospital
anymore
• Aldehydes
–
–
–
–
Inactivates proteins and DNA
Examples: formaldehyde, glutaraldehyde
Highly effective but classified as hazardous
Used as a general purpose high-level disinfectant
18
Chemical disinfectant classes
• Quaternary ammonium compounds
(“quats”)
– Benzalkonium chloride - Zephiran
– Disrupts the cell membrane
– General purpose low-level disinfectant, applied
with a squirt bottle, left on for 10 minutes
• Metals
– Combine with -SH groups, denature proteins
– Examples: silver nitrate ointments, mercury
(mercurochrome), copper
– Used on burns; doesn’t sting or irritate skin
19
Common hospital chemical
disinfectants/sterilants
• Peracetic acid/hydrogen peroxide (Acecide®, Endospor®,
Peract®) for high-level
• Glutaraldehyde (old Cidex®, MetriCide®) for high-level
• Hydrogen peroxide (Clorox, STERRAD) for intermediatelevel
• Ortho phthalaldehyde (OPA, new Cidex®) for high level
• Peracetic acid (Soluscope 3® endoscope processor) for
high-level
• Improved peroxide (Oxivir TB®, Chlorox Healthcare®)
spray for low-level
20
Types of devices to be reprocessed
•
•
•
•
•
Flexible endoscopes
ERCP scopes
Cystoscopes
Vaginal probes
Laryngoscope
blades
• Bronchoscopes
• All made of
materials that you
cannot autoclave
21
The reprocessing process; high-level
disinfection
1.
2.
3.
4.
5.
•
Cleaning
Disinfection
Rinsing
Drying
Storage
Inspection at
each step
22
The reprocessing process; cleaning
• The most important step in the reprocessing of
medical items and equipment is not disinfection
or sterilization
• The most important step is cleaning
– Removal of organic material (bioburden, biofilm)
using water and detergent or enzymatic cleaner plus
scrubbing (friction) with brushes
– You cannot disinfect or sterilize something that is dirty
– Example; you must presoak dirty items at the point of
use to prevent drying of bioburden in transport
23
The reprocessing process; cleaning
• In the reprocessing area, there are some
machines that can clean some instruments
– Some claim to be washer-sterilizers
– Ultrasonic cleaner machines
• How clean is clean?
– There are no practical ways to measure cleaning
•
•
AAMI says <6.4 ug of protein per cm2 is clean
How do you measure that?
• Current controversy; should cleaning be done by
non-specialists at the point of use or by
specialists in the central reprocessing area?
24
The reprocessing process; disinfection
• Manual chemical
– After cleaning, the scope
is soaked in a high-level
disinfectant
– A very error-prone
process
– Temperature, expiration
date, concentration,
time of exposure, PPE all
must be perfect
– Requires special air
handling
25
The reprocessing process; disinfection
• Automated chemical
– Olympus OER-Pro, Steris
System 1 and Reliance,
Evotech, Soluscope 3
– Machines are designed
for each scope, hook up
to each channel, run the
chemical through, rinse,
dry
– More reliable than
manual, but expensive,
not all scopes are
compatible with each
machine
26
The reprocessing process; storage
• Flexible endoscopes must be
stored vertically in a clean
cabinet
– Prevents water drops in the
channels, microbial growth
– Absolutely cannot throw them
in a drawer or put them in the
box they were shipped in
– Shown; regular case and drying
case that forces dry air through
the channels
27
The reprocessing process; sterilization
1.
2.
3.
4.
5.
6.
Cleaning
Inspection
Packaging
Sterilization
Sterile Storage
Quality indicators
28
Challenges to reprocessing
•
•
•
•
•
Many of the devices have internal channels
Materials compatibility
Failure of the device over time; inspection
No good way to scrub some parts
Human factors; personnel are not trained,
certified, or paid well and work in poor conditions
• Desired turnaround time does not allow for
adequate reprocessing
• Reprocessing machines are expensive
29
Challenges to reprocessing
• Ambulatory surgery centers and other off-site
settings
• No good way to do quality control
• Manufacturers instructions for use do not work
• Reliance on flash sterilizing rather than buying
enough instruments
• Infection preventionist is not involved enough
• Transport of contaminated instruments
• Not presoaking instruments
• Reprocessing single-use devices
30
CDC Guidelines
• 2008 Guideline for Disinfection and Sterilization in
Healthcare Facilities
– http://www.cdc.gov/hicpac/pdf/guidelines/Disinfection_N
ov_2008.pdf
• Association for the Advancement of Medical
Instrumentation
– http://www.aami.org/
• Interim Protocol for Healthcare Facilities Regarding
Surveillance for Bacterial Contamination of
Duodenoscopes after Reprocessing
– http://www.cdc.gov/hai/pdfs/cre/interim-duodenoscopesurveillance-Protocol.pdf
31