NTA Level 5 • Semester 1 • PST05103

Introduction to Antisepsis, Disinfection and Sterilization

Pharmaceutical Microbiology • Source Session/Topic 42

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Session 42: Introduction to Antisepsis, Disinfection and Sterilization

Total Session Time: 60 minutes

Pre-requisites

• Human anatomy and physiology

Students Learning Tasks

By the end of this session students are expected to be able to:

• Define sterilisation

• Distinguish between sterilisation, disinfection and, antisepsis

• Outline procedures for disinfection and sterilisation of

pharmaceutical equipment

• List factors affecting sterilisation and disinfection

Resources Needed:

• Flip charts, marker pens, and masking tape

• Black/white board and chalk/whiteboard markers

SESSION OVERVIEW

SESSION CONTENTS

STEP 1: Presentation of Session Title and Learning Tasks (5 minutes)

READ or ASK students to read the learning tasks and clarify

ASK students if they have any questions before continuing

STEP 2: Antisepsis and Disinfection (15 minutes)

• Antisepsis

o Antisepsis is deﬁned as destruction or inhibition of

microorganisms on living tissues having the effect of limiting or

preventing the harmful results of infection

o Antisepsis is not a synonym for disinfection

• Disinfection

o Disinfection is the process of removing microorganisms, including

potentially pathogenic ones, from the surfaces of inanimate

objects

o The British Standards Institution further deﬁnes disinfection as

not necessarily killing all microorganisms, but reducing them to a

level acceptable for a deﬁned purpose, for example, a level which

is harmful neither to health nor to the quality of perishable

goods

• Chemical disinfectants are capable of different levels of action

o High level disinfection

▪ High level disinfection processes destroy vegetative

bacteria, mycobacteria, fungi and enveloped (lipid) and

nonenveloped (nonlipid) viruses, but not necessarily bacterial

spores. High level disinfectant chemicals (also called

chemical sterilants) must be capable of sterilization when

contact time is extended. Items must be thoroughly cleaned

prior to high level disinfection

o Intermediate level disinfection

▪ indicates destruction of all vegetative bacteria including

Mycobacterium tuberculosis but may exclude some viruses and

fungi and implies little or no sporicidal activity

o Low level disinfection

▪ Low level disinfectants kill most vegetative bacteria and

some fungi as well as enveloped (lipid) viruses (e.g.,

hepatitis B, C, hantavirus, and HIV)

▪ Low level disinfectants do not kill mycobacteria or

bacterial spores

▪ Low level disinfectants are typically used to clean

environmental surfaces

• Procedures for disinfection

o Selection of appropriate disinfectant

o Washing with clean water to remove visible soil e.g. pus, blood

o Diluting disinfectant appropriately (according to manufacturer’s

recommendations) using sterile water

o Immersing the items to sterilized in the disinfectant solution for

the recommended time

o Removing disinfected items from the disinfectant solution using

gloved hands or disinfected/sterilized forceps

o Rinsing the disinfected using sterile water (or water previously

boiled for 20 minutes and cooled) to remove traces of

disinfectants

o Placing the disinfected items in a previous sterilized/disinfected

container with lid

STEP 3: Sterilization (30 minutes)

• Sterilization is the process where all the living microorganisms,

including bacterial spores are killed or removed from a particular

product, package or a medical equipment

• The product being sterilized becomes sterile i.e. devoid of any viable

form of microorganisms

• Acceptable performance for sterilization is that a sterilization

process should provide for a probability of finding a nonsterile unit

less than 1 in 1 million

• Sterilization is absolute, the sterilized item is either sterile or

not, there is no semi sterilized or almost sterilize phenomena

• Sterility is therefore absence of viable forms of life

• Sterilization can be achieved by physical, chemical and physiochemical

means

• Chemicals used as sterilizing agents are called chemisterilants

• Sterilization is an essential stage in the processing of any product

for parenteral administration, or for contact with broken skin,

mucosal surfaces, or internal organs, where the threat of infection

exists

• Sterilization processes involve the application of a biocidal agent or

physical microbial removal process to a product or preparation with

the object of killing or removing all microorganisms

• Main methods used in sterilization include;

o Heat sterilization

o Chemical sterilization

o Irradiation sterilization

o Filtration sterilization

• Sterilization may therefore involve elevated temperature, reactive

gas, irradiation or ﬁltration through a microorganism-proof ﬁlter

• The success of the sterilization process depends on a suitable choice

of treatment conditions, e.g. temperature and duration of exposure

• Factors that affect sterilization include;

o Number of microbes

▪ The more microorganisms are present the more difficulty it

is to eliminate them. It takes more time or stronger

sterilization effect

o Type of microbes

▪ Endospores are very difficult to eliminate

▪ Vegetative bacteria have different susceptibility to

sterilization methods

o Environmental influence

▪ Presence of organic matter e.g. blood, pus, faeces affect

sterilization

o Time of exposure

▪ Chemical and radiation sterilization are more effective at

longer times of exposure.

▪ In heat sterilization, longer times compensates for lower

temperatures

• Procedure for sterilization of instruments

o Cleaning of instruments as per procedure for cleansing of

instruments

▪ Instruments that are not clean cannot be sterilized

o Performing hand hygiene and apply gloves

▪ Hands should be as clean as possible to prevent

contamination of clean instruments/equipment.

o Placing the clean instruments/equipment in the appropriate

sterilization package and sealed

▪ Sealed packaged items will maintain sterility after

sterilization has been achieved until opened for use. If

packaging becomes wet or damaged, sterility cannot be ensured.

Instruments in damaged packages must be re-sterilized or

discarded. Packaging should be appropriate for type of

sterilizer used.

o Placing temperature sensitive chemical indicators for each load to

be sterilized

▪ Temperature sensitive chemical indicators provide an

immediate visual check to ensure package has been processed.

The colour change demonstrated by a chemical indicator does

not ensure that the processed items have been sterilized. Only

an appropriate biological indicator can confirm that the

sterilization cycle has been successful.

o Loading the sterilizer evenly (avoiding overloading the chamber)

according to manufacturer’s directions for loading the chamber

▪ Overloading the sterilizer will prevent effective

sterilization; there must space between the packages

o Starting the sterilization process

▪ Sterilizing time, temperature, pressure and cycles may vary

depending on the type of sterilizer used

▪ Manufacturer’s instructions must be followed at all times

▪ With dry heat and autoclave sterilization, time starts when

the appropriate temperature has been reached

o Removing instruments from sterilizer after the sterilization cycle

has been completed

▪ Ensure items are dry before removing from the unit

▪ Sterilized instruments may become contaminated when wet

packaging is handled.

o Storing sterilized items in a clean, dry place that is protected

from dust, dirt, and moisture. Sterile items must be stored off

the floor

▪ Handling increases the chances of punctures of sterilized

bags. Sterilized items must be stored separately from dirty

equipment/instruments.

o Recording information about each sterilization cycle in the log

book

▪ Each load must be monitored by recording temperature,

pressure, cycle length, etc.

STEP 4: Key Points (5 minutes)

• Antisepsis is deﬁned as destruction or inhibition of microorganisms on

living tissues having the effect of limiting or preventing the harmful

results of infection

• Disinfection is the process of removing microorganisms, including

potentially pathogenic ones, from the surfaces of inanimate objects

• Sterilization is the process where all the living microorganisms,

including bacterial spores are killed or removed from a particular

product, package or a medical equipment

• Sterilization processes involve the application of a biocidal agent or

physical microbial removal process to a product or preparation with

the object of killing or removing all microorganisms

STEP 5: Evaluation (5 minutes)

• What is antisepsis?

• What is high level disinfection?

• What are the factors that affect sterilization process?

References

Hugo and Russell (2011), Pharmaceutical Microbiology 8th Edition, Willey-

Blackwel publications

Karen C. Carroll et al (2013); Jawetz, Melnick and Adelberg’s Medical

Microbiology 26th Ed. McGraw Hill Co. Inc.

Greenwood et al (2012); Medical Microbiology, 18th edition Churchill

Livingstone

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