microbio unit 11A - methods of microbial control: preventing + controlling microorganisms

I: methods to prevent microbial infection

sterilization

removal or destruction of all forms of microbial life

what is the most resistant microbe to sterilization? why?

bacillus + clostridium; endospores

disinfection

destruction of vegetative pathogens; disinfection of the number of microbes on a surface

disinfectants are applied to what?

fomites (door handles, toilet seats, etc.)

are sterilization and disinfection the same? why?

no, sterilization kills microbes while disinfection limits the number of microbes

antiseptic

chemical disinfection of the skin, mucous membranes, living tissue; reduces the number of microbes

what is an example of an antiseptic?

mouth wash, idoine

asepsis

object or area free of pathogens

sanitiziation

reduction of pathogens to safe public health levels (restaurant glassware, utensils)

bacteriocydal

to kill bacteria

bacteriostatic

inhibit the growth of bacteria

how do you eliminate prions?

temperature must be at 134C + items must be soaked in a strong sodium hydroxide solution

why is mycobacterium resistant?

contains a waxy cell wall which allows it to resist phagocytosis

how are protozoan cysts resistant?

have an outer coating that allow them to resist or hide from body immune mechanisms

what is the least resistant microbe?

viruses with lipid envelopes

what are the different types of moist heat?

boiling, autoclaving

what does moist heat do to proteins?

breaks amino acid peptide bonds → denatures them

boiling

100C water for 10 minutes

what things do we boil to control microbes?

cups, dishes, basins

why is boiling things not reliable?

bacteria with endospores may not be eliminated

autoclaving

121C for 15 minutes for 15 psi → steam under pressure

what things do we autoclave?

culture media, equipment, linens

pasteurization

72C for 15 seconds → high temperature short time (HTST)

what things do we pasteurize?

milk, cream, beer

how come sterilization and pasteurization are not the same?

sterilization kills all microbes whereas pasteurization only lowers bacterial counts

what does pasteurization do?

eliminates milk-borne pathogens (brucella, cocciella, mycobacterium tuberculosis) + lowers bacterial counts to prolong the quality of refrigerated milk

dry heat

direct flame

what are examples of dry heat?

incineration, cremation

what things do we apply dry heat to?

ovens, pipets, glassware

is dry heat 100% effective?

yes

filtration

filters with pores small enough to retain microbes from liquids or gases

what things do we use filtration for?

enzymes, vaccines, antibiotic solutions

low temperature

bacteriostatic → stops microbial reproduction

what things do we use low temperature on?

food, some medications

dessiccation

remove water → bacteriostatic

what is an example of dessiccation?

freeze drying

what things do we use dessiccation on?

food

osmotic pressure

hypertonic solutions

what are some things we use osmotic pressure for?

food preservation

what are some examples of osmotic pressure?

salt brines + sugar solutions

radiation

non-ionizing + ionizing light

non-ionizing

loooonnnng wavelength

what is an example of non-ionizing radiation?

uv light

can uv light penetrate into surfaces?

no

what things we use non-ionizing light on?

uv light used in OR/autopsy room, certain equipment

ionizing

short wavelength; replaces gas sterilization

what is an example of ionizing radiation?

gamma rays

can ionizing radiation penetrate surfaces?

yes

what do we use ionizing radiation on?

foods (spices), disposables, medical supplies

phenol

carbolic acid

why is carbolic acid rarely used?

because it costs a lot and has a strong odor

where is carbolic acid used?

throat lozengers (local anesthetic)

instead of phenol, what derivatives to we use?

cresol, lysol

what phenol antiseptic derivative do we use?

hexachlorophene (pHisoHex)

why don’t we use hexachlorophine excessively?

causes neurological damage

what phenol derivative do we use on surgical scrubs?

chlorohexidine

what are the phenol derivatives?

throat lozenders, cresol, lysol, hexachlorophene (pHisoHex),chlorohexidine, triclosan

what phenol derivative do we use in antibacterial soaps?

triclosan → organisms have more recently become resistant to this

what essential oils contain phenol derivatives?

pine, orange, peppermint oil

what are some halogens used to disinfect?

iodine, chlorine

iodine (betadine)

antiseptic/disinfectant

chlorine

effective disinfectant found in bleach

what does chlorine combine with to make hypochlorous?

water

alcohol

used as an antiseptic + disinfectant; used to swab skin + clean equipment

what does alcohol kill?

bateria + fungi, but NOT endospores and certain viruses

what is the % of alcohol in ethanol, isopropanol, or rubbing alcohol

60-95%

tincture

alcohol added to another chemical → increases the effectiveness of the chemical

heavy metals

silver, mercury, copper

heavy metals are used as an ________ or _________

antiseptic, disinfectant

where are heavy metals used in controlling microbes?

1% silver nitrate → eyes of newborns; will kill nisseria gonorrhea

what heavy metal do we use to clean fish tanks and pools?

copper sulfate

surface active agents

soaps + detergents → mechanical removal (rubbing, scrubbing, rinsing) + emulsifiers

quaternary ammonium compounds (QUATS)

antimicrobial, odorless, colorless, tasteless, non-toxic

where do we use quaternary ammonium compounds?

mouthwashes like zephiran

zepharin is also known as what?

benzalkonium chloride

organic compounds

food preservation compounds

what are some food preservation compounds?

sorbic acid, sodium benzoate, sodium nitrate

sorbic acid + sodium benzoate

used in cheese + soda

what organic compound is used in meat?

sodium nitrate

aldehydes

most effective antimicrobial agent

what aldehydes are used to control microbes?

formaldehyde (formalin is formaldehyde dissolved in water → embalming fluid)

glutaraldehyde

how long does it take for glutaraldehyde to become cidal?

10 mins

what does glutaraldehyde become in 3-10 hours?

endosporocydal

gases

highly penetrating + carcinogenic

what gas did we once use to disinfect medical supplies?

ethylene oxide

oxidizing agents

chemicals that contain oxygen

what are examples of oxidizing agents?

hydrogen peroxide, ozone, benzoyl peroxide

hydrogen peroxide

antiseptic + disinfectant

ozone

disinfection of water (used in conjunction with chlorine)

benzoyl peroxide

acne medications