Control of Microbial Growth Flashcards
what is sterilization?
destruction or removal of all viable organisms
what is disinfection?
killing, inhibition, or removal of disease causing organisms`
what are disinfectants?
agents, usually chemical, used for disinfection on inanimate objects (typically)
what is sanitization?
reduction of the microbial population to levels deemed safe based on public health standards
what is antisepsis?
prevention of infection of living tissue by microorganisms
what are antiseptics?
chemical agents that kill or inhibit growth of microorganisms when applied to tissue
how is chemo used as antimicrobial agents?
use of chemicals to kill or inhibit growth of microorganisms within host tissue
what do -cidal agents do?
kills bacteria
what do -cidal agents do?
kills bacteria
what are examples of cidal agents?
bactericides, fungicides, and viricides
what does -static indicate?
a growth inhibiting agent
what is the pattern of microbial death?
microorganisms are not killed instantly
population death typically occurs exponentially
is a measure of an agents killing efficiency
make sure that viable but noncultural cells are dead
what is decimal reduction time?
the time it takes to kill 90% of cells
what does filtration do?
reduces microbial population or sterilizes solutions of heat-sensitive materials by removing microorganisms
also used to reduce microbial populations in the air
what are membrane filters?
porous membranes with defined pore sizes that remove microorganisms primarily by physical screening
what are some examples of air filters?
surgical masks
high-efiicienctb particulate air (HEPA) filters
what are some examples of using moist heat as control?
pasteurization
boiling
steam sterilization
what does moist heat destroy?
viruses, fungi, bacteria
NOT endospores
how does moist heat work?
degrades nucleic acids, denatures proteins, and disrupts membranes
steam sterilization
carried out above 100 degrees C which requires saturated steam under pressure
effective against all types of microbes
pasteurization
controlled heating at temperature well below boiling
used for milk, beer, and other beverages
process does not sterilize but kills pathogens present and slows spoilage y reducing the total load of organisms present
dry heat sterilization
less effective than moist heat sterilization, requires higher temperatures and longer exposure time
oxidizes cell constituents and denatures proteins
does not corrode glasswares and metal instruments as moist heat does
what is an example of dry heat sterilization?
flaming out inoculating loops
ultraviolet radiation
260 wavelength is most bactericidal
causes thymine dimers preventing replication and transcription
limited to surface sterilization because it doesn’t penetrate glass, dirt films, water, or other substances
used for water treatment
ionizing radiation
gamma radiation penetrates deep into objects
destroys bacterial endospores; not always effective against viruses
used for sterilization and pasteurization of antibiotics, hormones, sutures, plastic disposable supplies, and food
what has overuse of antiseptics caused?
selection for resistant bacteria
phenolics
commonly used as laboratory and hospital disinfectants
act by denaturing proteins and disrupting cell membranes
tuberculocidal, effective in presence of organic material, and long lasting
disagreeable odor and can cause skin irritations
alcohols
among the most widely used disinfectants, antiseptics, and sanitizers
bactericidal, fungicidal, but not sporicidal
can inactivate some viruses
denature proteins and possibly dissolve membrane lipids
halogens (iodine)
skin antiseptic
oxidizes cell constituents and iodinates proteins
may kill endospores at high concentrations
skin damage, staining, and allergies may be a problem
what is iodophor?
iodine complexed with organic carrier
released slowly to minimize skin burns
halogens (chlorine)
oxidizes cell constituents
important in disinfection of water supplies and swimming pools, used in dairy and food industries, effective household disinfectant
destroys vegetative bacteria and fungi
gas is sporicidal
heavy metals
mercury, silver, arsenic, zinc, copper
effective but usually toxic
combine with and inactivate proteins; may precipitate cell proteins
quaternary ammonium compounds
detergents that have broad spectrum antimicrobial activity and are effective disinfectants
amphipathic organic cleansing agents
what are cationic detergents?
effective disinfectants that kill most bacteria, but not M. tuberculosis or endospores
stable and non-toxic, inactivate by hard water and soap
aldehydes
commonly used agents are formaldehyde and glutaraldehyde
highly reactive molecules
sporicidal and can be used as chemical sterilants
sterilizing gases
used to sterilize heat-sensitive materials
microbicidal and sporicidal
ethylene oxide sterilization is carried out in equipment resembling an autoclave
vaporized hydrogen peroxide can also be used
what are some examples of natural control mechanisms?
predation by Bdellovibrio
viral-mediated lysis using pathogen specific bacteriophage lysins
toxin-mediated killing using bacteriocins
what are the conditions that influence the effectiveness of antimicrobial agents?
population size
-larger=longer to kill
population composition
concentration or intensity of an antimicrobial agent
-higher concentrations kill faster
contact time
-longer exposure=more killed
temperature
-higher temps=enhanced chem activity
how does local environment affect the effectiveness of antimicrobial activity?
pH, viscosity, concentration of organic matter, etc., van profoundly impact effectiveness
organisms in biofilms are less susceptible
