Ignatz Semmelweiz
required all personnel at the obstretics ward in the
Vienna General Hospital to wash their hands with chlorinated
lime.
Joseph Lister
initiated aseptic surgery which included heat sterilization
of surgical instruments and the application of phenol (carbolic
acid) to wounds following surgery.
Microbial control needed for?
is needed to prevent the transmission of
infection, contamination, an spoilage. involves killing, preventing growth or removing microbes.
Sterilization
is the process of destroying or removing all
forms of microbial life on an object or in a material, including the destruction of endospores.
degree of sterilization?
Sterilization is absolute; there are no degrees of sterilization.
Methods of sterilization
a. moist heat, 121C for 15 minute at 15 PSI
b. dry heat, 170C for 120 minutes
c. ionizing radiation
d. gases such as ethylene oxide
Disinfection
is the process of destroying vegetative
pathogens, but not necessarily endospores or viruses.
disinfectant
is usually a chemical applied to an object or a
material. tend to reduce or inhibit growth. are usually a liquid chemical solution applied to a surface or to eliminate pathogens in water, for example, by
chlorination
Antisepsis
refers to chemical disinfection of the skin, mucous
membranes, or other living tissues.
Antiseptic
is the chemical used in antisepsis treatment.
Germicide
is a chemical agent that rapidly kills microbes but
not necessarily their endospores. ex.VIRUCIDE kills viruses.
Bacteriostasis
is a condition in which bacterial growth and
multiplication are inhibited, but the bacteria are not killed. ex. Refrigeration ( Most microbes do not reproduce at 0 to 7C)
Fungistasis
refers to the inhibition of fungal growth
Asepsis
(without infection) refers to the absence of pathogens
from an object or area
ASEPTIC TECHNIQUES
are designed to prevent the entry of
pathogens into the body.ex. air filtration, ultraviolet lights, personal masks, gloves and gowns, instrument sterilization
Degerming
is the removal of transient microbes from the
skin by mechanical cleansing or by the use of an antiseptic.
- Alcohol swabs are often used on the skin before injection.
- Iodine-containing products are often used before surgery.
Sanitization
is the reduction of pathogens to safe public
health levels on eating utensils by mechanical cleansing or
chemicals
Temperature effect on microbial growth
1. Cold, like refrigeration, controls microbial growth
2. Biochemical reactions occur more rapidly at warm
temperatures.
3. Disinfectant activity is enhanced by warm temperatures
What type bacteria more susceptible to disinfectants?
Gram-positive bacteria are generally more susceptible to
disinfectants than gram-negative bacteria
Pseudomonas
can even grow in some disinfectants and antiseptics.
- This resistance is probably related to the much smaller
porins (structural openings in outer membrane).
- not only survive in quats, but actively grown in them
Mycobacterium
group of nonendospore forming
organism that exhibit greater than normal resistance to
disinfectants
Environment affect chemical control agents?
- Organic matter and pH level frequently interfere with the
actions of chemical control agents.
- Examples of such organic matter include vomit, feces, pus,
and food
Physiological State of the Microbe to control it
- An actively growing microorganism tends to be more
susceptible to disinfectants than an older microbe.
- Endospores are more resistant to chemical agents and
physical methods than vegetative cells.
Ex. Endospores of Clostridium botulinum can withstand
b
3 ways microbial agent affect the microbes
Alteration of Membrane Permeability, Damage to Proteins and Nucleic Acids , Heat.
Alteration of Membrane Permeability
- The susceptibility of the plasma membrane is due to its lipid
and protein components.
- Certain chemical control agents, such as quaternary
ammonium compounds, damage the plasma membrane by
altering its permeability
Damage to Proteins and Nucleic Acids
- Some microbial control agents damage cellular proteins by
breaking hydrogen, covalent, and disulfide bonds, which are
essential for the molecular structural and functional integrity.
- Other agents interfere with DNA and RNA replication and
protein synt
THERMAL DEATH POINT (TDP)
is the lowest temperature at which all the bacteria in a liquid culture will be killed in 10 minutes
THERMAL DEATH TIME (TDT)
is the length of time required to kill all bacteria in a liquid culture at a given temperature
DECIMAL REDUCTION TIME (DRT or D value)
is the length of time in minutes, which 90% of a bacterial population will be killed at a given temperature
Moist Heat Sterilization
kills more quickly because the water hastens the
breaking of hydrogen bonds that hold proteins in their 3-
dimensional structure.
Uses for moist heat sterilization:
- kills vegetative forms of bacterial pathogens,
many viruses, and fungi and fungal spores within
about 10 minutes.
- It is less effective against endospores and some
viruses.
Autoclaving (steam under pressure)
is the most effective method of moist heat sterilization. kill all organisms and their endospores in about 15 minutes or longer depending on the type and volume of material being sterilized.
Pasteurization:
-Louis Pastuer developed the method.
- High-temperature, short-time (HTST) pasteurization is used
to pasteurize milk-- @ 72C for about 15 seconds.
- Milk that can be stored without refrigeration can be
sterilized by ultra high temperature (UHT) treatment
Dry Heat Sterilization:
kills by oxidation effects
a. Direct flaming: used to sterilize inoculating loops
b. Incineration: Burn to ashes; used to sterilize and dispose
of contaminated paper cups, bags, and dressings
Filtration:
- Filtration is the passage of a liquid or gas through a screenlike material with pores small enough to retain microorganisms.
- Membrane filters are composed of substances such as
cellulose esters or plastic polymers.
uses of filtration
- Used to sterilize heat-sensitive materials such as some culture media, enzymes, vaccines, and antibiotic solutions.
- High-efficiency particulate air (HEPA) filters remove almost all microbe larger than about 0.3 cm in diameter. filter viruses, and even
Deep-freezing
is an effective method for preserving microbial
cultures (quick-frozen between -50 and -95C)
Lyophilization
a. Most effective method for long-term preservation of microbial cultures.
b. Water is removed by high vacuum at low temperature
Dessication:
- Involves removing water from microbes.
- Microbes are not capable of growth or reproduction, but can
remain ?viable? for ?years...primarily? bacteriostatic.
- The gonorrhea bacterium can withstand dryness for only
about an hour.
- The tuberculosis bacte
Osmotic Pressure:
- Microbes in high concentration salts and sugars will lose
water (Plasmolysis).
- Molds and yeasts are more capable of growing in materials
with low moisture or high osmotic pressure than bacteria
are.
- Fruit and grain are spoiled by molds rather than b
IONIZING RADIATION:
- gamma rays or high-energy wavelengths
- They are used to sterilize pharmaceuticals and disposable dental and medical supplies such as plastic syringes, gloves, suturing materials, and catheters.
- not widespread in routine sterilization.
- destroys the
NONIONIZING RADIATION:
- has a longer wavelength than 1 nm. ex. Ultraviolet (UV) light
- UV light causes adjacent thymines in DNA chains to from
bonds creating thymine dimers, inhibit correct replication of the DNA during reproduction of the cell.
- UV radiation is used to cont
Chemical agents
are used to control microbes on living tissue and inanimate objects. Few chemical agents achieve sterility; most of them reduce microbial populations to safe levels or remove vegetative forms of pathogens from objects
Disk-diffusion Method:
- A disk of filter paper is soaked with a chemical agent and
placed on the surface of an agar plate that has been inoculated with a test organism.
- Incubate and measure a clear zone representing the inhibition of growth (zone of inhibition) around the di
Use-Dilution test:
- current standard for evaluating effectiveness
of disinfectant.
- Several test bacteria are added to a series of tubes containing increasingly strong concentrations of the test disinfectant.
- The tubes are incubated and growth or lack of it is recorded.
organisms used in use- dilution test
1. Staphylococcus aureus (gram + organism)
2. Salmonella typhi (gram - organism)
3. Pseudomonas aeruginosa (gram - organism resistant to
antimicrobials
Phenol (carbolic acid)
- It is seldom used today as an antiseptic or disinfectant
because it irritates the skin and has a disagreeable odor.
- In concentrations above 1%, has an antibacterial
effect
Phenolics
- are derivatives of phenol that has been chemically altered to reduce its irritating qualities.
- Phenolics and phenol exert antimicrobial activity by
injuring plasma membranes, inactivating enzymes, and
denaturing proteins
- are suitable agents for disi
two examples of phenolics
1. One of the most frequently used phenolics is derived from
coal tar = CRESOLS. It is a very good surface disinfectant.
- The cresol O-phenylphenol is the main ingredient in Lysol
2. Another phenolic is hexachlorophene, which consists of
two molecules of
Chlorhexidine:
- Used for disinfection of skin and mucous membranes.
- It is combined with a detergent or alcohol for surgical hand
scrubs and preoperative skin preparation.
- Mechanism of Action - damages plasma membranes by
blocking an enzyme needed for lipid synthesi
two types of halogens
chlorine and iodine
Iodine (I):
- halogen
- is effective against all kinds of bacteria, many
endospores, various fungi, and some viruses
- Mechanism of action: iodine combines with the amino
acid tyrosine and, thus inhibits protein function.
Betadine and Isodine
- iodine chemical disinfectant
- Main use: skin disinfection and wound treatment
hypochlorous acid ( chlorine)
- Germicidal action is caused by the hypochlorous acid
(HOCl) that forms when chlorine is added to water.
- HOCl is a strong oxidizing agent that prevents functioning
of much of the cellular enzymes.
- HOCl is the most effective form of chlorine because i
Calcium hypochlorite (chlorine)
-chlorine compound.
-Calcium hypochlorite (Ca(OCl)2) is used to disinfect
dairies, barns, slaughterhouses, and restaurants eating
utensils.
Sodium hypochlorite (chlorine compound)
-Sodium hypochlorite (NaOCl) is used as a household
disinfectant and as a bleach (Chlorox), as a disinfectant in
dairies, food processing establishments, and hemodialysis
systems.
make drinkable water in a emergency?
- Can use 2 drops of bleach/liter of water (4 drops/liter if the
water is cloudy) to render water safe
- Let chlorinated water sit for 30 minutes before using
Chloramines
- consist of chlorine and ammonia
- used as disinfectants, antiseptics, or sanitizing agents.
- are very stable compounds that release chlorine over long
periods of time.
- are relatively effective in organic matter
- Chloramines are toxic to aquarium fis
Alcohols
- effectively kill bacteria and fungi but not endospores and
nonenveloped viruses.
- Mechanism of action: protein denaturation, disruption of
membranes and dissolve many lipids including the lipid
component of enveloped viruses.
-recommended optimum conce
advantage and disadvantage of Alcohol
- Advantage: evaporates rapidly and leaves no residue.
- Unsatisfactory when applied to wounds because they cause
coagulation of a layer of protein under which the bacteria
continue to grow
1% silver nitrate ( Heavy metals)
- solution is antiseptic. A few drops are put into newborns' eyes to guard against a gonococcal infection of
the eyes
Copper sulfate (Heavy metals)
is used chiefly to destroy green algae that
grows in reservoirs, swimming pools, and fish tanks
(concentration of one part per million)
Zinc Chloride (Heavy metals)
is common ingredient in mouthwash.
Zinc oxide ( Heavy metals)
is used as an antifungal agent in paints
Surface-active agents or surfactants
- decreases surface tension among molecules of a liquid
- includes soaps and detergents
- function in the mechanical removal of microbes through
scrubbing...dergerming
- may contain Triclocarban which inhibits gram+ bacteria
- Acid-anionic surface-active
Quaternary Ammonium compounds (quats)
- are cationic detergents. NH4+
- They are modifications of the four-valence ammonium ion
- Quats are strongly bactericidal against gram(+) bacteria; they are less strong against gram(-) bacteria.
- They are also fungicidal, amoebicidal and virucidal agai
Organic acids and derivatives:
- used as preservatives to control mold growth.
- Sorbic acid, Benzoic acid, Parabens ,Calcium propionate.
- Mechanism of action: inhibits enzymatic and metabolic
activity
Sorbic acid
(or its salt, potassium sorbate) is used to inhibit
mold growth in acidic foods such as cheese. Organic acids
Benzoic acid
(or its salt, sodium benzoate) is an antifungal
and is effective at low pH levels and is used in soft drinks and
other acidic foods. Organic acids
Parabens
such as methylparaben and propylparben are
used to inhibit mold growth in liquid cosmetics and shampoos. Organic acids
Calcium propionate
prevents mold growth in bread. Organic acids
Aldehydes
- Examples are formaldehyde and glutaraldehyde.
- Mechanism of action: inactivate proteins by forming covalent
crosslinks with a number of organic functional groups of
proteins.
Formaldehyde
- gas, is an excellent disinfectant.
- It is more commonly used as formalin.
- Formalin was used to preserve biological specimens,
embalm corpses, and inactivate bacteria and viruses in
vaccines
- It is tissue irritating, has poor penetration, slow action
Glutaraldehyde:
- is less irritating and more pleasant to handle
than formaldehyde.
- used to sterilize hospital instruments, including respiratory
therapy equipment.
- 2% solution (Cidex) is bactericidal, tuberculocidal,
virucidal in 10 minutes and sporicidal in 3 to 10
Gaseous sterilant
- ethylene oxide
- Depends on denaturation of proteins and involves
replacement of labile hydrogen in the proteins with alkyl groups
- used on objects with heat can damage
- Ethylene oxide kills all microbes and endospores.
Oxidizing Agent
- Exert antimicrobial activity by oxidizing cellular components of treated microbes.
- Examples of oxidizing agents are ozone (O3) and hydrogen
peroxide (H2O2)
Hydrogen peroxide
- is a poor antiseptic for open wounds
because it is quickly broken down to water and gaseous O2
by catalase, which is present in human cells.
- Hydrogen peroxide is an effective disinfectant when used
to disinfect inanimate objects. It can even be sporic
Examples of oxidizing agents:
- Zinc peroxide and hydrogen peroxideare useful in irrigation of deep wounds where the release of oxygen inhibits the growth of anaerobic bacteria.
- Benzoyl peroxide is also useful in the treatment of
wounds infected by anaerobic pathogens. (acne)