Download Sterilization and Disinfection Group 5 Meynard Guanlao Euodia

Sterilization and
Disinfection
Group 5
Meynard Guanlao
Euodia Guinmapang
Ma Annelly Clara Guinto
Christine Pia Hechanova
Rosa Mistica Hemoso
2B
Sterilization
Sterilization pertains to the destruction of all microorganisms in or about an
object, as by steam (flowing or pressurized), chemical agents (alcohol, phenol, heavy
metals, ethylene oxide gas), high-velocity electron bombardment, or ultraviolet light
radiation.
Disinfection
Disinfection, on the other hand, is the destruction of pathogenic microorganisms
or their toxins or vectors by direct exposure to chemical or physical agents.
Difference between antiseptic and disinfectant
Disinfectants are those chemicals that destroy pathogenic bacteria from
inanimate surfaces while antiseptics are those chemicals that can be safely applied over
skin and mucus membranes.
AGENTS THAT MODIFY FUNCTIONAL GROUPS OR PROTEINS
AND NUCLEIC ACIDS
1. Heavy Metals
Heavy metals (e.g. mercury, silver, arsenic, copper, and tin) bind irreversibly to the
sulfhydryl groups of proteins. Because the sulfhydryl groups are often at the active site
of an enzyme, the binding of heavy metal results in enzyme inactivation, affecting vital
chemical reactions required for bacterial survival. These compounds are toxic and are
mostly used topically.
Examples include merthiolate, mercurochrome, copper sulfate, and silver nitrate
(which is highly bactericidal for gonococci).
A. Mercurials
In general,relatively few mercury compounds have anti-bacterial activity, and those
result of the presence of mercuric ion are primarily bacteriostatic rather than
bacteriocidal.
Merthiolate is a mercury-containing substance that was once widely used as germkiller in a range of products, including topical antiseptic solutions and antiseptic
ointments for treating cuts, nasal sprays, eye solutions, vaginal spermicides, and diaper
rash treatments; and a preservative in many different products, including vaccines and
other injectable biological products, such as Rho(D)-immune globulin preparations. The
poisonous ingredient of merthiolate is thimerosal. Merthiolate poisoning occurs when
large amounts of the substance are swallowed or come in contact with the skin.
Poisoning may also occur if you are exposed to small amounts of merthiolate constantly
over a long period of time. The FDA banned the use of merthiolate in over-the-counter
products in the late 1990s. Symptoms include abdominal pain, diarrhea, decreased
urine output, drooling, extreme difficulty breathing, metallic taste, memory problems,
mouth sores, seizures, shock, skin numbness, severe swelling within the throat, thirst,
walking problems, and vomiting.
Mercurochrome is the trade name of merbromin (an organomercuric disodium salt
compound and a fluorescein) and (usually) of merbromin tinctures made of merbromin
and alcohol or water (usually 2% merbromin to 98% alcohol or water). It is a topical
antiseptic used for minor cuts and scrapes. It is no longer sold in the USA because of its
mercury content. When applied on a wound, the dark red colour stains the skin, making
the detection of any erythema or inflammation, indicative of infection, more difficult. It is
also used as a biological dye used to mark tissue margins, and as a metal dye in
industrial dye penetrant inspection to detect metal fractures.
B. Silver Nitrate
Silver nitrate, also known as lunar caustic, is a soluble chemical compound with
chemical formula AgNO3. It is called lunar caustic because silver was called luna by the
ancient alchemists.
Silver salts have antiseptic properties. Until the development and widespread
adoption of antibiotics, dilute solutions of AgNO3 used to be dropped into newborn
babies' eyes at birth to prevent contraction of gonorrhoea from the mother. Eye
infections and blindness of newborns was reduced by this method; incorrect dosage,
however, could cause blindness in extreme cases. Fused silver nitrate, shaped into
sticks, was traditionally called "lunar caustic". It is used as a cauterizing agent, for
example to remove granulation tissue around a stoma. Dentists sometimes use silver
nitrate infused swabs to heal oral ulcers. Silver nitrate is also used by some podiatrists
to kill cells located in the nail bed.
However, silver nitrate is toxic and corrosive and could caused some adverse
reactions. It could cause burning and skin irritation. Brief exposure to the chemical will
not produce immediate or even any side effects other than the purple skin stains, but
with more exposure, side effects will become more noticeable, including burns. Longterm exposure may cause eye damage. Short contact can lead to deposition of black
silver stains on the skin. Absorbed silver nitrate can cause Hyponatremia and
Methemoglobinemia.
Symptoms of overdose include pain and burning of the mouth, salivation,
vomiting, diarrhea, shock, coma, convulsions, and death; blackening of skin and
mucous membranes. Fatal dose is as low as 2 g.
Must be stored in a dry place. Store in a tight, light-resistant container. Exposure
to light causes silver to oxidize and turn brown, dipping in water causes oxidized film to
readily dissolve.
Mechanism of Action:
Free silver ions precipitate bacterial proteins by combining with chloride in tissue
forming silver chloride; coagulates cellular protein to form an eschar; silver ions or salts
or colloidal silver preparations can inhibit the growth of both gram-positive and gram-
negative bacteria. This germicidal action is attributed to the precipitation of bacterial
proteins by liberated silver ions. Silver nitrate coagulates cellular protein to form an
eschar, and this mode of action is the postulated mechanism for control of benign
hematuria, rhinitis, and recurrent pneumothorax.
Pharmacodynamics/Kinetics:
Absorption: Because silver ions readily combine with protein, there isminimal GI
and cutaneous absorption of the 0.5% and 1% preparations
Excretion: Highest amounts of silver noted on autopsy have been in kidneys,
excretion in urine is minimal
Dosage:
Children and Adults:
Sticks: Apply to mucous membranes and other moist skin surfaces only on area to be
treated 2-3 times/week for 2-3 weeks
Topical solution: Apply a cotton applicator dipped in solution on the affected area 2-3
times/week for 2-3 weeks. Applicators are not for ophthalmic use.
C. Copper Sulfate
Copper(II) sulfate is the chemical compound with the formula CuSO4. This salt
exists as a series of compounds that differ in their degree of hydration. The anhydrous
form is a pale green or gray-white powder, whereas the pentahydrate, the most
commonly encountered salt, is bright blue. The anhydrous form occurs as a rare mineral
known as chalcocyanite. The hydrated copper sulfate occurs in nature as chalcanthite
(pentahydrate), and two more rare ones: bonattite (trihydrate) and boothite
(heptahydrate).
Copper sulfate is a fungicide used to control bacterial and fungal diseases of
fruit, vegetable, nut and field crops. Some of the diseases that are controlled by this
fungicide include mildew, leaf spots, blights and apple scab. It is used in combination
with lime and water as a protective fungicide, referred to as Bordeaux mixture, for leaf
application and seed treatment. Copper sulfate is a naturally-occurring inorganic salt
and copper is an essential trace element in plant and animal nutrition. It is available in
the following formulations: dusts, wettable powders, and fluid concentrates.
Copper sulfate is only moderately toxic upon acute oral exposure. The lowest
dose of copper sulfate that has been toxic when ingested by humans is 11 mg/kg.
Ingestion of copper sulfate is often not toxic because vomiting is automatically triggered
by its irritating effect on the gastrointestinal tract. Some of the signs of poisoning include
a metallic taste in the mouth, burning pain in the chest and abdomen, intense nausea,
vomiting, diarrhea, headache, sweating, shock, discontinued urination leading to
yellowing of the skin. Injury to the brain, liver, kidneys and stomach and intestinal linings
may also occur.
Copper sulfate can be corrosive to the skin and eyes. Skin contact may result in
itching or eczema and some allergic reactions. Eye contact with this material can
cause: conjunctivitis, inflammation of the eyelid lining, excess fluid buildup in the eyelid;
cornea tissue deterioration due to breaks, or ulceration, in the eye's mucous membrane;
and clouding of the cornea.
Vineyard sprayers experienced liver disease after 3 to 15 years of exposure to
copper sulfate solution in Bordeaux mixture. Chronic exposure to low levels of copper
can lead to anemia. Examinations of copper sulfate-poisoned animals showed signs of
acute toxicity in the spleen, liver and kidneys.
Absorption of copper sulfate into the blood occurs primarily under the acidic
conditions of the stomach; the mucous membrane lining of the intestines acts to some
extent as a barrier to absorption of ingested copper. After ingestion, more than 99% of
copper is excreted in the feces. It is stored primarily in the liver, brain, heart, kidney and
muscles. About one-third of all the copper in the body is contained in the liver and brain.
Another third is contained in the muscles. The remaining third is dispersed in other
tissues.
2. Oxidizing Agents
A. Halogens
i. Chlorine
Chlorine in an aqueous solution, which even in a very small amount, exhibits fast
bactericidal action. Its activity is greater at pH (4-7). However, its mechanism of activity
has not been fully determined. Organic matter and alkaline detergents can reduce its
effectiveness. There are three types of chlorine compound – the elemental chlorine Cl2,
hypochlorous acid (HOCl) and hypochlorite ion (OCl-).
Their disinfectant action is due to the liberation of free chlorine. It can also exert
its effect by the irreversible oxidation of SH groups of essential enzymes. Its primary
mode of action is against both the structural and functional proteins in the surface or
intracellular. Sulhydral groups of essential enzymes appear to be particularly targeted,
as well as nitrogen interactions on amino acids. Even low concentrations have dramatic
effect on the activities of metabolic enzymes in vitro. Direct protein degradation into
smaller peptides and precipitation have shown and are believed to be the main mode of
its action against prions. Other observed effects are cell wall and membrane disruption
by attacking structural proteins, lipids and carbohydrates.
When chlorine is added to water, it forms hypochlorous acid. Exactly how
hypochlorous acid destroys microorganisms has never been demonstrated
experimentally, but it has been speculated that hypochlorous acid allows oxygen to
emerge, which in turn supposedly combines with components of cell protoplasm,
destroying the organism. Hypochlorous acid has also been found to disrupt oxidative
phosphorylation and other membrane-associated enzymes activities. Further effects
have been reported on nucleic acids, including the formation of including the formation
of chlorinated derivatives of nucleotide bases. Studies of specific effects on the growth
of E. Coli have shown inhibition of bacterial growth by hypochlorous acid.
Researchers have assumed that because of the low chlorine level required for
bactericidal action, chlorine must inhibit some key enzymatic reactions in the cell. The
inhibition of these essential cytoplasmic metabolic reactions is largely responsible for
the destruction of both bacterial and fungal cells. Very few chemicals are considered
sporicidal; however, bacterial spores are affected by disinfectants at different stages in
the sporulation process. While not considered sporicidal, chlorine compounds have
demonstrated some activity at the outgrowth stage, but higher concentrations also may
prevent germination. Chlorine compounds have been shown to affect surface antigen in
enveloped viruses and DNA as well as structural alterations in non-enveloped viruses.
Being the most useful of the chlorine compounds, hypochlorites are widely used
in the food and dairy industries for sanitizing dairy and food processing equipment. They
are employed as sanitizers in most households, hospitals and public buildings (ex.
Chlorox).
ii. Iodine
Iodine is the most effective halogens available for disinfection. It is a highly
reactive element that precipitates proteins and oxidizes essential enzymes. It exists
principally in the form of I2. It is used as bactericidal agent against organisms and it can
penetrate the cell wall of microorganisms rapidly. And its action is maximal at values
below pH 6. The rate of its killing decreases as the pH is increased above 7.5. Its
activity can be reduced in the presence of some organic and inorganic compounds like
serum, feces, ascetic fluid, sputum, urine, sodium thiosulfate and ammonia. It is usually
complex with a carrier called iodophor.
The actual killing of the microorganism by iodine could be the result of the
inability to synthesize proteins due to oxidation of important amino acids (particularly
lysine, histidine, cysteine and arginine). It cause protein disruption and loss of structure
and function. Some of this effect includes: the increase bulk of the amino acid
molecules which leads to the denaturation of DNA, or the addition of iodine to
unsaturated fatty acids could to lead to a change in the physical properties of the lipids.
Electron microscopy observations support the conclusion that iodine, by interacting with
the double bonds of phospholipids causes damage of the cell wall which lead to a loss
of intracellular material.
The principal use of iodine is in the disinfection of the skin like in the surgical
procedure.
B. Hydrogen Peroxide
Hydrogen peroxide (H2O2) is a very pale blue liquid, slightly more viscous than
water, which appears colorless in dilute solution. It is a weak acid and with strong
oxidizing properties, and is a powerful bleaching agent. This oxidizing properties of
hydrogen peroxide allows it to destroy a wide range of pathogens and permits it to be
used to sterilize heat or temperature sensitive particles. Also, it is used as a disinfectant,
antiseptic, oxidizer, and in rocketry as a propellant.
Hydrogen peroxide’s antibacterial action is secondary to its oxidizing ability as
well as formation of a more toxic free hydroxyl radical from the peroxide in an irondependent reaction. For its mechanism of action, it acts on the microorganisms through
its release of nascent oxygen. Hydrogen peroxide produces hydroxyl-free radical that
damages proteins and DNA.
The biggest advantage of hydrogen peroxide as a sterilizer is the short cycle
time. Whereas the cycle time for ethylene oxide (discussed above) may be 10 to 15
hours, the use of very high concentrations of hydrogen peroxide allows much shorter
cycle times. Some hydrogen peroxide modern sterilizers even have a cycle time as
short as 28 minutes. Moreover, this is used at 6% concentration to decontaminate the
instruments, equipments such as ventilators. 3% Hydrogen Peroxide Solution is used
for skin disinfection and deodorising wounds and ulcers. Strong solutions are sporicidal.
DISADVANTAGE:
The oxidizing capacity of hydrogen peroxide is so strong that it is considered a
highly reactive oxygen species. Also its oxidizing property causes some material
compatibility issues and users should consult the manufacturer of the article to be
sterilized to ensure that it is compatible with this method of sterilization. Furthermore,
the penetrating ability of hydrogen peroxide to not as good as ethylene oxide and so
there are limitations on the length and diameter of lumens that can be effectively
sterilized and guidance is available from the sterilizer manufacturers. Also, it easily
decomposes in light, broken down by catalase, proteinaceous organic matter drastically
reduces its activity