Microbiology: Exam 3

Joseph Lister

revolutionized surgery by introducing methods to prevent infection of wounds using carbolic acid

sterilization

removal or destruction of all microorganisms and viruses; does not consider prions

disinfection

elimination of most or all pathogens; some viable microbes may remain

disinfectant/germicide

chemicals used on inanimate objects

antiseptic

chemicals used on living tissue

decontamination

reduces number of pathogens to a safe level; washing, use of heat, chemicals

sanitization

substantially reduces microbial population to meet accepted health standards that minimize spread of disease; not a specific level of control

preservation

process of delaying spoilage of perishable products; conditions of storage, addition of bacteriostatic preservatives

pasteurization

brief heating to reduce number of spoilage organisms; destroy pathogens without changing characteristics of product

BSL 1

procedures for work with microbes not known to cause disease in healthy people

bsl 2

procedures for work with moderate risk microbes that cause disease but have limited potential for transmission

bsl 3

procedures for work with pathogens that cause serious or potentially fatal disease through inhalation

bsl 4

procedures for work with easily transmitted deadly pathogens

temperature and pH on disinfectants

influences effectiveness

bacterial endospores

most resistant; only extreme heat or chemical treatment destroys them

protozoan cysts and oocysts

resistant to disinfectants; excreted in feces; causes diarrheal disease if ingested; destroyed by boiling

mycobacterium species

waxy cell walls makes it resistant to many chemical treatments

pseudomonas species

resistant to and can actually grow in some disinfectants

non enveloped viruses

lack lipid envelope; more resistant to disinfectants

d value (decimal reduction time)

time required to kill 90% of population under specific conditions

critical items

contact body tissues; must be sterile

semicritical instruments

contact mucous membranes; must be free of microorganisms and viruses; some endospores may remain

non critical instruments

contact unbroken skin; low risk of transmission

sterility

absence of living organisms in or on an object

sanitizer

chemical used on food handling utensils and surfaces to reduce bacteria to acceptable public health standards

bactericidal

agent that kills bacteria

bacteriostatic

agent that inhibits bacterial growth without necessarily killing them

selecting the appropriate germicidal chemical

toxicity, compatibility, cost/availability, storage and stability, environmental risk

sterilants

destroy all microbes; also called sporocides; heat sensitive critical instruments

high level disinfectants

destroy viruses and vegetative cells; semicritical instruments

intermediate level disinfectants

destroy vegetative bacteria, mycobacteria, fungi, and most viruses; non critical instruments

low level disinfectants

destroy fungi, vegetative bacteria except mycobacteria, and enveloped viruses; furniture, floor, walls

most effective concentration of ethanol and isopropanol

70%

phenol coefficient

compares any agent to effectiveness of phenol

filter paper method

disks soaked with agent are placed on a lawn of bacteria before growth

use dilution test

agent is diluted, microbes are exposed to the dilutions, then incubated

properties of an ideal disinfectant

fast acting, effective against many microbes without destroying tissues or being poisonous, high penetrance without damaging the object, easy to prepare and stable, inexpensive and easy to obtain/use, no unpleasant odor

hydrolysis chemical agents (protein denaturation)

acids, alkalis

oxidation chemical agents (protein denaturation)

hydrogen peroxide, potassium permanganate, halogens, heavy metals

alkylation chemical agents (protein denaturation)

formaldehyde, some dyes

surfactants (membrane disruption)

soaps, alcohols, phenols, detergents, quaternary ammonium compounds

wetting agents (membrane disruption)

detergents

soap

dissolves lipids; contains alkali and sodium

cationic detergents

disinfect food utensils; do not kill endospores but do kill some viruses; includes quats

anionic detergents

used for laundry and household cleaning; less effective at sanitizing than cationic detergents

lactic and propionic acid

used as food preservative

benzoic acid

used to inhibit fungal growth in soda, ketchup, margarine

sorbic acid and sorbates

used to inhibit fungal growth in cheeses

silver nitrate

treats gonococcal ophthalmia neonatorum; replaced by antibiotics given at birth

selenium sulfide

kill fungi and fungal spores; used to treat skin infections and dandruff in shampoos

copper sulfate

controls growth of algae in heating and air conditioning systems and barnacles on boats

merthiolate and mercurochrome

kills vegetative cells in skin wounds but not endospores or mycobacterium; prepared as a tincture (dissolved in alcohol)

thimerosol

organic compound used to disinfect skin and instruments and preserve vaccines and contact lens solutions

phenylmercuric nitrate, mercuric naphthenate

laboratory disinfectants

hypochlorous acid (chlorine bleach)

controls growth of microbes in drinking water and swimming pools; disinfects food utensils and dairy equipment

chloramine (chlorine and ammpnia)

wound cleansing, root canal therapy, water treatment

chlorine

destroys all microorganisms, endospores, and viruses

iodophors

slow release compounds with iodine combined with organic surfactants; less irritating

fluorides

added to drinking water, toothpaste, and other treatments to kill bacteria in mouth that cause tooth decay

methyl bromide gas

fumigates soil used for bedding plants

alcohols

denature protein when mixed with water, dissolve lipids and membrane; used to disinfect skin

tincture

antimicrobial chemical dissolved in alcohol

phenolics

disrupt cell membranes, denature proteins; disinfect surfaces and discarded cultures

amphyl

kills vegetativek cells, fungi, viruses

lysol

kills vegetative cells, fungi, viruses

creosote

carcinogenic cresol wood preservative

hexachlorophene and dichlorophene

halogenated phenols inhibit staphylococci and fungi

triclosan

kills bacteria, not viruses or fungi

oxidizing agents

disrupt disulfide bonds in proteins

hydrogen peroxide

forms supe4roxide radicals to kill microbes

potassium permanganate

disinfects instruments, or in low concentrations, skin

alkylating agents

disrupt proteins and nucleic acids; not used on tissue

ethylene oxide

used as a gas to sterilize materials that are sensitive to heat or chemicals

acridine

mutates dna; can be used to clean wounds

methylene blue

inhibits growth of some bacteria

crystal violet

blocks cell wall synthesis in bacteria, inhibits growth of gram positive bacteria

thymol

used as a preservative

eugenol

used in dentistry to disinfect cavities

sulfites and sulfur dioxide

used as food preservatives

sodium diacetate

retards mold growth in bread

sodium nitrite

preserves cured meats and cold cuts, but is converted into carcinogens in the body

dry heat

171C for 1 hour, 160 C for 2 hours, 121 C for 16 hours or more

moist heat

more penetrating and faster than dry heat; 15-20 minutes at 121C; autoclave

flash method of pasteurization

product is heated to 71.6C for at least 15 seconds

holding method of pasteurization

product is heated to 62.9C for 30 minutes

high pressure processing

decreases number of microorganisms in commercial food products

refrigeration

slows microbial growth without killing microbes

freezing

does not kill bacteria but prevents them from growing

drying

preserves food by eliminating wate4r to inhibit enzyme activity; does not kill endospores

freeze drying

drying materials while in the frozen state

UV radiation

kills viruses and bacteria by damaging dna and proteins, but many bacteria have dna repair mechanisms

ionizing radiation

energetic enough to remove electrons from atoms, damaging dna

microwave radiation

energy is absorbed by water and reemitted as heat

sonic waves

destroy bacteria if sufficient intensity but not practical for sterilization

filtration

sterilizes materials that would be damaged by heat

membrane filter

has pores small enough to stop passage of microbes

depth filters

thick porous filtration material that uses electrical charges to trap cells

high efficiency particulate air filters

filters microbes from air

osmotic pressure

kills microbes in hyperosmotic medium

taxonomy hierarchy

domain, kingdom, phyla, class, order, family, genus, species