Biol 300 Chapter Eight Notes Flashcards

microbial growth and replication are targets for what?

control

what are the three ways controlling microorganisms can occur?

1. chemically

2. physically/mechanically

3. biologically

control of microorganisms can be in the form of what three things?

1. inactivation

2. growth

3. killing of organism

what are biocides?

all agents used to control microorganisms

what is sterilization?

process by which all living cells, spores, viruses, destroyed or removed (from an object or habitat)

what is disinfection?

the killing, inhibition, or removal of microorganisms that may cause disease, usually by treatment of inanimate objects

two facts about disinfection:

1. disinfectants don’t necessarily sterilize

2. there is a substantial reduction in microbes

what is sanitization?

the reduction of microbes to levels considered safe by public health standards

what is antisepsis?

the destruction or inhibition of microbes on living tissue to prevent infection by killing/inhibiting pathogen growth

two facts about antisepsis:

1. reduces total number of microbes

2. not as toxic as disinfectants, don’t want to harm host

what is chemotherapy?

the use of chemicals to kill/inhibit growth of microbes

what are bacteriocides, fungicides, viricides, etc. ?

antimicrobial agents that kill

what are bacteriostatic, fungistatic, etc.?

antimicrobial agents that do not kill but instead inhibit growth

fact about what are bacteriostatic, fungistatic, etc.

if the agent is removed growth resumes

what are the types of physical removal methods?

• filtration

• membrane filters

• filtering air

what is filtration?

1. reduces (not kills) microbial population or sterilizes solutions of heat-sensitive materials by removing microorganisms

2. also used to reduce microbial populations in air

what are membrane filters?

1. porus membranes with defined pore sizes that remove microorganisms primarily by physical screening

2. solution suctioned through filterby vacuum

3. 0.22 μm filter needed to remove bacteria, however viruses are not removed

example of a type of membrane filter

Higher Efficiency Particulate air (HEPA)

what are HEPA filters?

1. used in laminar flow biological safety cabinets

2. can remove particles as small as viruses

3. used when sterile environment is needed (ORs, NASA clean rooms)

examples of filtering air?

• HEPA filters

• surgical masks, N95s, etc.

• cotton plugs on culture vessels, pipettes

fact about surgical masks & N95s

these exclude 95% of particles larger than 0.3 μm

types of physical control methods:

• heat

• pasteurization

• tyndallization

• dry heat sterilization

• radiation

what is heat in terms of a physical control method?

1. destroys viruses, fungi, and bacteria

2. degrades nucleic acids, denatures proteins, and disrupts membranes

true or false, boiling will not destroy spores and does not sterilize

true

what is an example of heat in terms of a physical control method?

steam sterilization

info about steam sterilization

• carried out at or above 121ºC; requires saturated under pressure (121ºC, 15 psi)

• autoclave

• effective against all types of microorganisms (including spores)

• quality control includes indicators

what is autoclave?

water boils, creates steam in chamber; temp/pressure remains (20 minutes)

what is pasteurization?

• controlled heating at temps well below boiling, 55-60ºC

• used for wine, milk, beer, and other bevs

• kills pathogens present and slows spoilage by reducing the total organisms present

does pasteurization steralize?

no

what is tyndallization?

• used for those objects that cannot withstand high temps

• used to kill endospores through process of intermittent sterilization

what is intermittent sterilization?

• sterilization by heating to boiling 2-3 times in 24 hours in 30-60 min intervals so that any resistant spores/vegetative cells may germinate and be destroyed

• in b/w rounds, any spores germinated are subsequently killed in the next round of heat exposure

what is dry heat sterilization?

• oxidizes cell constituents and denatures proteins

• bench top incinerators used to sterilize inoculating loops

is dry heat sterilization less effective than most heat sterilization?

yes

why is dry heat sterilization less effective than most heat sterilization?

because it requires higher temps and longer exposure times; items subjected to 160-170ºC for 2-3 hours

what is radiation?

the emission or transmission of energy in the form of waves or particles through space or a material medium

two types of radiation:

• ultraviolet (UV)

• gamma (ionizing)

what is uv?

• uv limited to surface sterilization (it does not penetrate glass)

• has been used for water treatment

wavelength of about what is the most bactericidal?

260

what prevents replication and transcription in terms of uv?

case thymine dimers

what is gamma radiation (ionizing)?

• gamma radiation penetrates deep into objects

  • destroys vegetative cells, bacterial endospores

is gamma radiation effective against viruses?

not always

what is gamma radiation used for?

sterilization and pasteurization of antibiotics, hormones, sutures, plastic disposable supplies, food

main difference between UV and gamma radiation:

UV penetrates only the surface for sterilization while gamma penetrates deep into objects

info about chemical control methods:

• can be used to sterilize, disinfect, or as antiseptic

• effective chemical agents act on a broad spectrum at low concentration, but not toxic to hosts

• involves treatment of disease as well as food preservation

what do you ideally want with chemical control methods?

• stable compound

• odorless (or pleasant smell)

• soluble in water and lipids

• low surface tension

• low cost

types of chemical control methods:

• phenol/phenolics

• alcohols

• halogens

• heavy metals

• quaternary ammonium compounds

• aldehydes

• sterilizing gases

info about phenol/phenolics:

• commonly used as lab and hospital disinfectants

• act by denaturing proteins and disrupting cell membranes

• tuberculocidal, effective in presence of organic materials, long-lasting

• disagreeable odor and can cause skin irritation

• ex —> lysol, chlorhexidine

info about alcohols:

• among the most widely used disinfectants, antiseptics, sanitizers

• two most common are ethanol and isopropanol

• bactericidal, fungicidal, but not sporicidal, most effective concentration 60-80%

• inactive against some viruses

• denature proteins and possibly dissolve membrane lipids

info about halogens:

• important antimicrobial agents

• any of five elements —> fluorine, chlorine, bromine, iodine

• iodine and chlorine most often used

info about iodine:

• skin antiseptic

• at high concentrations, may kill spores

• usually used as tincture as 2% or iodophor

• skin damage, staining, allergies can be a problem

info about chlorine:

• used for disinfection of water supplies and swimming pools

• used for disinfection in dairy/food industries

• effective household disinfectant

info about heavy metals:

• mercury, silver, arsenic, zinc, copper

• effective but can still be toxic

• silver sulfadiazine used to treat burns

• copper sulfate used in pools to kill algae

info about quaternary ammonium compounds:

• detergents with antimicrobial activity

• effective disinfectants

• kill most bacteria, but not TB or endospores

info about aldehydes:

• commonly used agents are formaldehyde and glutaraldehyde

• highly reactive molecules, deactivate nucleic acids, proteins

• sporicidal and can be used as chemical sterilants

info about sterilizing gases:

different types of gases used:

• ethylene oxide gas

• chlorine dioxide gas

• vaporized hydrogen peroxide

info about ethylene oxide gas:

• used to sterilize heat-sensitive materials

• used for instruments/machines, plastics, catheters, etc .

• bacteriological and sporicidal

info about chlorine dioxide gas:

• used in hospitals, labs

• mold remediation in homes

• used in buildings after anthrax scare (2001)

info about vaporized hydrogen peroxide:

• used to decontaminate biological safety cabinets

• used in hospitals/ORs, labs

• kills a wide variety of microbes