Sterilization and Disinfection
Sterilization and Disinfection
Sterilization and Disinfection
Mic r
n t r o l
C o
Dr. R. Tan
Primary target of microbial control
Microorganisms capable of causing infection or
spoilage that are constantly present in the external
environment and on the human body
Disinfection
- refers to the use of physical process or chemical agent
(disinfectants) that promotes killing, inhibition, or
removal of pathogenic microorganisms (usually on
inanimate objects) but not bacterial endospore
Sanitization
- is any cleansing technique that mechanically removes microorg.
to reduce the level of contaminants / microbial population to a
safe level as determined by public health standards
Sepsis – growth of microorganisms or the presence of
microbial toxins in the blood and other tissues
2. Nature of microorganism
- the efficacy of a chemical agent depends on these
properties: specie , growth phase of culture, and
presence of special structure (such as spores and
capsules), and the number of the organisms in the
test system
3. Temperature
- the killing of bacteria by chemical agents increases
with an increase in temperature
- for each 10°C increase in temperature, there is
doubling of the death rate
4. pH
- Hydrogen ion concentration influences bactericidal action
by affecting both the organism and the chemical
agent
- Some disinfectants are more effective at alkaline pH
(glutaraldehyde) while others are more effective at acid pH
(e.g. phenols)
5. Time
- when bacteria are exposed to a specific concentration of a
bacterial agent, even in excess, not all organisms die at the
same time; rather, there is a gradual decrease in the
number of living cells
2. Incineration / cremation
- burn to ashes
- useful for decontaminating infected lab. Animals
incubate at 37°C
(to allow spores to germinate to form new vegetative cell)
Lyophilization ( Freeze-drying )
A process used for preserving biological material, by
removing the water from the sample, which involves
first freezing the sample and then drying it, under a
vacuum, at very low temperatures
RADIATION
- defined as energy emitted from atomic activities and
dispensed at high velocity through matter or space
-Sunlight possesses appreciable bactericidal activity and
plays an important role in the spontaneous
sterilization that occurs under natural conditions
-2 types
Ionizing radiation: Radiation that have sufficient energy to
remove an electron completely from an atom and
produce an electrical charge (ionization)
Nonionizing radiation: Energy absorbed by the molecule
cannot remove an electron completely, the
excitation produced often leads to
photochemical changes
Ionizing radiation
- Ex: electromagnetic rays: X-ray, alpha, beta & gamma rays
- uses short wavelength
- much higher energy content than UV rays
- has greater power penetration
- can penetrate a solid barrier, bombard a cell, enter it, and
dislodge electrons from molecules
Diguanides
- have antimicrobial activity against vegetative bacteria,
yeasts, protozoans and enveloped viruses but not against
spores, protozoan cysts and mycobacteria
- They function by disrupting cytoplasmic membrane to cause
cell leakage and may enter cells to cause coagulation of the
cell cytoplasm
- It may be used together with surface active disinfectants at
a concentration of 1 – 4%
- Ex. chlorhexidine which is more effective at pH 7 – 8
used as a safe antiseptic to apply to prevent body infection
and in oral rinses for treating sore gums and mouth ulcers
and preventing plaque on teeth
II Phenolic compound
- at low concentration, these compounds are rapidly
bactericidal causing leakage of cell contents and irreversible
inactivation of membrane-bound oxidases and
dehydrogenases
- Parent compound : Carbolic acid ( phenol )
- excellent for disinfecting feces, blood, pus, sputum &
other proteinaceous material
- primarily use for testing new bactericidal agent
- It had been replaced as a practical disinfectant by less
caustic and less toxic phenol derivative
- Cresols
- Xylenols
- Diphenyl compound
- Phenolics are effective against bacteria, fungi and virus
Phenol derivatives:
• Cresols
- the simplest of the alkyl phenols
- Ortho-, meta-, paracresols – are applicably more active than
phenol
- usually employed as a mixtureCresols obtained industrially
by the distillation of coal tar -- usual source of these products
- Cresols are used to dissolve other chemicals, as disinfectants
and deodorizers, and to make specific chemicals that kill Insect
pests
- sold under the trade names: Lysol and Creolin
• Xylenols
- Dimethylphenols
- important class of phenolics with great industrial importance
- are used as pesticides and in the manufacture of antioxidants
Kills
99.9
%
of
germ
30 se s in • A general purpose Disinfectant
cond
s • Kills most bacteria on surface
• Destroys odors, cleans and
disinfects against germs and
against staph
• Good septic tank
disinfectant
• Halogens
- chlorine and iodine are among the most useful disinfectants
- Almost exclusively bactericidal and effective against
sporulating bacteria, virus, fungi and protozoa
(1) iodine
- exist principally in the form of I2 at pH value below 6
where maximal bactericidal action is manifested
- iodine tinctures came into wide use as microbicides
- Iodine quickly kills a broad range of microorganisms
- destroys many microorganisms and viruses within 3-5 minutes
- used in cleansing skin or disinfecting small wounds but
presented with some problems
- strong smell and can stain skin and clothing.
- react to metals and are rather unstable
- skin irritant
Betadine Solution
- various mixtures and solutions of
iodine, called Iodaphores, have
been formulated that greatly lessen such
disadvantages and dangers
- enhance stability and microbe killing
properties.
- Water disinfectant
- hypochlorites - most useful of the chlorine compound
- widely used for sanitizing dairy products
and food processing equipment
- employed as sanitizers in most households,
hospitals, and public buildngs
- marketed as: Chlorox, Zonrox, Purex
• Hydrogen peroxide
- antibacterial action is secondary to its oxidizing
ability as well as formation of a more toxic free
hydroxyl radical from the peroxide in an iron-
dependent reaction
- It is a weak acid
- In a 3% solution, it is harmless but very weak
antiseptic whose primary clinical use is in the
cleansing of wounds
- It has strong oxidizing properties and is therefore a
powerful bleaching agent that is mostly used for bleaching
paper
Dyes
- some of the coal-tar dyes not only stain bacteria but are
inhibitory at very high dilutions
- within the usual pH range, the basic dyes are the most
effective
- their current medical use is limited primarily to the
treatment of dermatologic lesions
• Triphenyl methane dyes
• aniline dye derivatives especially Crystal violet, Malachite
green, Brilliant green
• Highly selective for gram (+) organisms
• Used in the laboratory in the formulation of selective
culture media
• Acidine dyes
• Often referred as Flavines because of their yellow color
• exert a bactericidal and bacteriastatic effect upon a
number of organisms
• Compounds of clinical use : proflavine, acriflavine
Alkalyting agent
- The lethal effect results from their alkylating action on
proteins
- Glutaraldehydes and formaldehydes are the most commonly
used aldehydes
-They are active against bacteria and their spores, viruses, fungi
and protozoa
-Antimicrobial activity occurs as a result of cross-linking proteins
and nucleic acids in fungi, protozoa and bacteria and capsid
nucleic acid complexes in viruses
-These effects are mediated predominantly via amine, sulfurhydryl
and carboxyl groups on microbial surface proteins
Formaldehyde
- One of the least agents acting on proteins
- commercially available in:
• aqueous solution containing 37% formaldehyde (Formalin)
• paraformaldehyde a poymer (contain 91-99% formaldehde)
- Formalin - used for preserving fresh tissues
- major component of embalming fluids
- when used in high concentration, it destroys all
organisms, including spore
- Used to inactivate virus in the preparation of vaccines
- As a gas – used to decontaminate rooms, buildings, fabrics,
and instruments
Glutaraldehyde
- used as “cold sterilant” for surgical instruments
- 10x more effective than formaldehyde as a bactericidal
and sporocidal agent and less toxic
Ethylene oxide
- Employed in gaseous sterilization, especially on
materials that would be damaged by heat
(polyethylene tubings, electric & medical instruments,b
iologicals and drugs)
- Active against all types of bacteria, including spores &
TB bacilli