MICROBIAL CONTROL
MICROBIAL CONTROL METHODS
Physical Control
Heat
Cold/Dessication
Radiation
Autoclave
Chemical Agents
Categories of chemicals
Household products (listed next page)
HOUSEHOLD PRODUCTS
CONTROLLING
MICROORGANISMS
Decontamination- the destruction, removal or
reduction in number of undesirable microbes
4 methods of decontamination
Sterilization
Disinfection
Sanitization
Degermation
STERILIZATION- Removal or destruction of all viable microbes
Autoclaving, ionizing radiation
DISINFECTION- Destruction of vegetative pathogens on an
inanimate object
5% bleach, boiling water
Disinfection does not usually kill bacterial spores whereas
sterilization destroys all organisms.
Difference between disinfection and sterilization?
Disinfection is only a reduction of microbial load on an object. An
object that has been disinfected is less likely to transmit infection
than one that hasn't but because there is only a reduction in the
number of microorganisms, there is no guarantee.
Sterilization is absolute. It means that ALL of the microorganisms
have either been removed or killed. A sterile object has NO viable
microbial cells present.
SANITIZATION is a cleansing technique that removes
microorganisms and debris from inanimate objects
Dishwashing, laundering clothes
Sanitizing your toothbrush is important because
bacteria can build up from daily use.
DEGERMATION cleansing technique that removes
microorganisms and debris from living tissue
Alcohol wipes, surgical handscrub
Here is a review of key concepts
of hand hygiene….
Health care-associated infections affect hundreds of
millions of patients worldwide every year. Infections
lead to more serious illness, prolong hospital stays,
induce long-term disabilities, add high costs to
patients and their families, contribute to a massive,
additional financial burden on the health-care
system and, critically, often result in tragic loss of life.
(WHO, 2009)
PHYSICAL CONTROL
HEAT
RADIATION
COLD/DESICCATION
Some things to consider if using
HEAT……
Can use moist heat or dry heat
Practical Concerns in the Use of Heat: Thermal
Death Measurements
Thermal death time (TDT): the shortest length of time
required to kill all test microbes at a specified
temperature
Thermal death point (TDP): the lowest temperature
required to kill all microbes in a sample in 10 minutes
Temperature and length of exposure must be
considered
Higher temperatures generally allow shorter
exposure times; lower temperatures generally
require longer exposure times
COMMON MOIST HEAT METHODS:
Nonpressurized
steam
Steam under
pressure
Boiling water
Pasteurization
COLD/DESSICATION
The main benefit of cold treatment is the slow growth of
cultures and microbes in food during processing and
storage.
Cold does not kill most microbes; freezing can actually
preserve cultures
Desiccation: dehydration of vegetative cells when directly
exposed to normal room air
Lyophilization: a combination of freezing and drying;
used to preserve microorganisms and other cells in a
viable state for many years
RADIATION
Radiation is energy emitted from atomic activities and dispersed at high velocity
through matter or space
Ionizing radiation (X rays, gamma rays, electron beams)
Ionizes water to release hydroxide
Damages DNA
Non-ionizing radiation (UV, 260 nm)
Damages DNA
Microwaves kill by heat; not especially antimicrobial
Many foods can be effectively sterilized by utilizing
the penetrating power of ionizing radiation.
AUTOCLAVE
Here is an example of
how to clean a tattoo
machine with an
autoclave
http://www.youtube.com/
watch?v=huStW067jI&feature=related
CHEMICAL AGENTS
Chemicals are divided based on their level of effectiveness and the
surfaces to which they are applied.
Antiseptics: microbicidal agents harmless enough to be applied
to the skin and mucous membrane; should not be taken
internally.
Alcohols, mercurials, silver nitrate, iodine solution, detergents.
Disinfectants: agents that kill microorganisms, but not
necessarily their spores, but are not safe for application to
living tissues; they are used on inanimate objects such as tables,
floors, utensils, etc.
Hypochlorites, chlorine compounds, lye, copper sulfate,
quaternary ammonium compounds, formaldehyde and phenolic
compounds.
CHEMICAL AGENTS CONT.
Chemotherapeutic agents (synthetic antibiotics):
antimicrobial agents of synthetic origin useful in the
treatment of microbial or viral disease. These are
examples:
sulfonilamides, isoniazid, ethambutol, AZT, nalidixic
acid and chloramphenicol.
Antibiotics: antimicrobial agents produced by
microorganisms that kill or inhibit other
microorganisms
These chemicals approach the ideal by having many of the following
characteristics: broad spectrum, low toxicity, fact action, penetrating abilities,
residual effects, stability, potency in organic matter and solubility.
Works Cited
Lowry, Doc. "Tattoo Machines & Guns : How to Clean a Tattoo Machine."
YouTube Broadcast Yourself. 15 Nov. 2008. Expert Village. 1 Apr. 2011
<http://www.youtube.com/watch?v=huStW067-jI>.
"Microbiology in the news." American Society for Microbiology. 30 Mar. 2011.
20 Apr. 2011 <http://www.asm.org/>.
Talaro, Kathleen P., Marjorie Kelly. Cowan, and Barry Chess. Foundations in
microbiology. Boston: McGraw-Hill, 2009.
Todar, Kenneth. "Control of Microbial Growth." Online Textbook of
Bacteriology. 24 Apr. 2011
<http://www.textbookofbacteriology.net/control.html>.
United Kingdom. World Nuclear Association. London SW1Y 4JH. World
Nuclear Association | Nuclear Power - a Sustainable Energy Resource. 1 Apr.
2011. 2 Apr. 2011 <http://www.world-nuclear.org/info/inf05.html>.
"WHO | World Health Statistics 2009." World Health Statistics 2009. 2009.
World Health Organization. 24 Mar. 2011
<http://www.who.int/whosis/whostat/2009/en/index.html>.