1

Disinfection and Sterilization in the Healthcare Environment

Richard A. Van Enk, Ph.D., CICDirector, Infection Prevention and Epidemiology,

Bronson Methodist Hospitalvanenkr@bronsonhg.org

2

ObjectivesYou 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

3

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

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 microorganisms6

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 heat-sensitive

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 sterile15

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 non-

critical 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

background16

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

20

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

intermediate-level• 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

21

Types of devices to be reprocessed

• Flexible endoscopes• ERCP scopes• Cystoscopes• Vaginal probes• Laryngoscope

blades• Bronchoscopes• All made of

materials that you cannot autoclave

22

The reprocessing process; high-level disinfection

1. Cleaning2. Disinfection3. Rinsing4. Drying5. Storage• Inspection at

each step

23

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

24

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?

25

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

26

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

27

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

28

The reprocessing process; sterilization

1. Cleaning2. Inspection3. Packaging4. Sterilization5. Sterile Storage6. Quality indicators

29

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

30

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

31

CDC Guidelines

• 2008 Guideline for Disinfection and Sterilization in Healthcare Facilities– http://

www.cdc.gov/hicpac/pdf/guidelines/Disinfection_Nov_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-duodenoscope-surveillance-Protocol.pdf