Ch 15 Control of Microorganisms

Ionizing Radiation

(gamma and x rays) are powerful and lethal penetrating forms of radiation that cause ions to develop in cells which disrupt and mediate irreversible chain breakage of nucleic acids and proteins

Antiseptic

A chemical that can be used on living tissues such as the skin to reduce the microbial load by inhibiting the growth or killing the microbes that are present

Disinfectant

A chemical used to treat inanimate objects such as table tops, floors, walls, and instruments. These are too destructive for the use on living tissue.

Antibiotic

A substance produced by a microorganism that is inhibitory to the growth of another microorganism

Antimicrobial Agent

A substance that interferes with metabolism and growth of a microorgnism which can result in either inhibiting its growth or killing it

Hydrogen Peroxide

Agent used in cleaning of wounds especially those colonized by anaerobic bacteria

Types of Antimicrobial agents

Antibacterial Antifungal Antiviral Antiprotozoal Antihelminthic

The mechanism of action of antimicrobial agents can include the following:

Cell wall damage Disruption of cytoplasmic membrane Denaturation of cellular proteins Nucleic acid damage Inhibition of enzyme action

Halogens

Chemical elements that have high affinity for electrons, and those used for antimicrobial activity include chlorine and iodine

What chemical agents are used to control microorganism?

Disinfectants, antiseptics, or sterilants

Microwaves

Don't have direct effect on microorganisms but rather kill them indirectly by heating the moisture inside the cell to a lethal temperature range.

Heat Methods used to control microorganisms

Dry heat methods and Moist heat methods

Dessication

Drying process in which microorganisms and its environment are rendered free of water. Microorganisms depend on moisture for metabolic activity, a lack f moisture inhibits microbial multiplication and can lead to cell death

Alcohols

Effective as skin antiseptics and is disinfectants for medical instruments such as thermometers. Antimicrobial activity of alcohol is due to its ability to denature proteins and dissolve membrane lipids

Gases

Ethylene oxide (Used for sterile artificial heart valves, catheters, and plastic products) Beta Propiolactone (Sterilize heat sensitive material such as plastic petri dishes and disposal syringes)

Aldehydes

Formaldehyde (3 to 40% aqueous solution is known as formalin and used for inactivating viruses in certain vaccines) Glutaraldehyde (used for disinfection of medical equipment )

Microcidal Agent

Have been killing effects of microorganisms and are designated by the suffix, -cidal which means to kill. Depending on what microorganism is destroyed we have for example, bactericidal and fungicidal agents. Bactericides , fungicides, and virucides are agents that kill these respective microorganism.

Microbial Heat Resistance

Heat resistance varies among different microorganisms and is measure by the thermal death point (TDP) and thermal death time (TDT).

Sterilization

Process by which all life forms are destroyed from some objects or environment. No degree of sterility

Degerming

Process by which microorganisms are mechanically removed from a limited area of the body such as an injection site on the skin using an alcohol soaked swab

Filtration

Process in which liquid or gas passes through a microbiological filter which has pores small enough to trap unwanted microorganisms. Used on those substances that are sensitive to destruction by heat,radiation or chemicals such as vaccines, enzymes, and antibiotic solutions.

Sanitization

Process of cleansing inanimate objects to reduce the size of potentially pathogenic microbial populations to levels judged safe by public standard.

Antisepsis

Process of destroying vegetative pathogen on living tissue

Disinfection

Process used to remove or destroy pathogenic microorganism usually from inanimate objects so that they do not pose a threat of disease

The action of antimicrobial agents is affected by a number of factors which include the following:

Size of microbial population Exposure time of the agent on the population Susceptibility of the population to the antimicrobial agent Ae of the microbial population Concentration of antimicrobial agent Presence of extraneous organic matter Environmental conditions such as pH, heat and moisture

Osmotic Pressure

Solution containing high salt or sugar concentration provide high osmotic pressure and when bacteria are placed in these solution, water flows from the bacterial cell into the salt or sugar solution.

Detergents

Synthetic chemicals acting as wetting agents are employed primary for cleaning surfaces.

Aseptic

The absence of pathogenic microorganisms

Sterile

The object or environment is free of life of every kind. There is no degree of sterility.

Septic

The presence of pathogenic microorganism in living tissue.

Low Temperatures

Those achieved by refrigeration and freezing are often applied in the preservation of foods, however the microbes in the food sources are not killed but just inhibited

Non- ionizing radiation

UV RAYS AND MICRO WAVES

Heat

Usually the most practical and efficient agent of sterilization. It kills microorganisms by inactivating metabolic components such as enzymes, or destroying essential cellular components like denaturing proteins.

Radiation

Various effects due to wavelength, intensity and duration of application

UV rays

Visible light 400-7000 nm. Most germicidal activity occurred at wave length around 260nm. Lethal effect is due to formation of thyme thyme dimers in DNA which causes mutation

Moist Heat Methods

Widely used as a physical agent because of its penetrating properties

Heavy Metals

With antimicrobial activity include mercury, silver and copper. Silver in the form Silver nitrate is used as an antiseptic and disinfectant

Betadine

antiseptic used to treat superficial wounds and for preparing areas of skin for surgery

freezing

between -10 to 0 C also inhibit microbial growth. Some are killed by extended freezing. Formation of ice crystals in cell that rupture cell membrane believed to be responsible for cell death

refigeration

between 4-8 C are used to slow down microbial growth

boiling water

boiling (100 C) will kill most vegetative bacteria and viruses in about 10 to 20 minutes. however spores are not destroyed

tincture of iodine

consists of 2 % iodine and sodium iodine disclosed in 70% ethyl alcohol

Iosan

dairy sanitation

Phenol

good surface disinfectants for inanimate objects. Phenols derivates called cresols are several times for germicidal than phenol. Compounds called bisphenol such as lysol, triclosan and hexachlorophene are combination of two phenol molecules

What are the variety of physical methods that are used to control microorganisms

heat, radiation, filtaration, low temperature, dissociation and osmotic pressure

TDP

lowest temperature at which all microorganisms in a particular liquid suspension will be killed in 10 minutes

TDT

minimal length of time for all bacteria in a particular liquid culture to be killed at a given temperature

autoclaving

moist heath method in which an autoclave is used to provide steam under pressure as the sterilizing agent. Operates at 121 C and 15psi which performs sterilization by destroying bacterial endospores

Two main groups of radiation

non-inonizing radiation such as ultraviolet rays and microwaves. ionizing radiation such as x rays and gamma rays

Dry Heat Methods

penetrate more slowly that moist heat and thus takes more time to kill microorganism by this method.

Ioprep

pre surgical scrubbing

Wescodyne

preoperative areas of skin preparation

incineration

process of destroying microorganisms by direct flaming. combustible bandages, designs, and fomites are subjected to this method

pasteurization

process to precent the spoilage of wine by undesirable contamination of microbes

Microstatic Agents

termed -static do not kill microorganisms, they only inhibit their growth. Depending on the microorganism being affected we can have bacteriostatic, fungistatic and so on. (fungistatic agent inhibits the growth of fungi)

iodine

used as a sin antiseptic and as a disinfectant for certain equipment. interacts with proteins by iodinating tyrosine which irreversibly inactivates many cellular proteins

dry heat sterilization

usually done in a hot air oven using a temperature of 160 C to 180 C for one hour. Used to sterilize inanimate products such as gauze dressings, powders and the like.

chlorine

when chlorine gas is mixed with mater it forms hypochlorous acid. in liquid form is widely used for purification of municipal water supplies.