microbiology: controlling microbial growth

refrigeration

0-7 degrees; inhibits metabolism (slows or arrests cell division); preservation of food or laboratory materials (solutions, cultures)

boiling

100 degrees at sea level; denatures proteins and alters membranes; cooking, personal use, preparing certain laboratory media

high-pressure

100-800 MPa; denatures proteins and can cause cell lysis; preservation of food

autoclave

121 degree for 15 min at 15 psi; denatures proteins and alters membranes; sterilization of microbiological media, heat-stable medical and laboratory equipment, and other heat-stable items

dry-heat oven

170 degrees for 2 hours; denatures proteins and alters membranes, dehydration, desiccation; sterilization of heat stable medical and laboratory equipment and glassware

cell membrane, proteins, nucleic acids

3 major targets of microbial control agents

organic material, temperature, pH, type of microbe

4 things that can affect the effectiveness of antimicrobial treatments

Halogens

Iodine, Chlorine, Fluorine; good at killing bacteria, fungi and most endospores, some viruses.

noncritical items

Items that are not required to be sterile because they do not penetrate intact tissues.

zone of inhibition

Region around a chemical saturated disc, where bacteria are unable to grow due to adverse effects of the compound in the disc.

cresols (methylated phenols) o-phenylphenol

active ingredients in Lysol; example of phenolics

reduce water activity

addition of salt or water; inhibits metabolism and can cause lysis; salted meats and fish, honey, jams and jellies

hyberbaric oxygen therapy

air pressure three times higher than normal; inhibits metabolism and growth of anaerobic microbes; treatment of certain infections (e.g., gas gangrene)

Ethylene oxide

alkylating agent that is used for gaseous sterilization; form of cold sterilization

antisepsis

application of antiseptic (antimicrobial chemical safe to use on living skin or tissue)

mercury

bacteriostatic, but toxic to the central nervous system, digestive and renal systems at high concentrations

freezing

below -2degrees; stops metabolism, may kill microbes; long-term storage of food, laboratory cultures, or medical specimens

Betadine

brand of povidone-iodine commonly used as a hand scrub by medical personnel before surgery for topical antisepsis of a patients skin before incision

quats

can kill bacteria, fungi, protozoans and enveloped viruses, but not endospores

sanitization

cleansing of fomites to remove enough microbes to achieve deemed safe for public health

autoclave, incineration, filtration

common forms of sterilization

povidone-iodine

commone iodophor includes wetting agent that releaes iodine relatively slowly

silvadene cream

commonly used to treat topical wounds and is particularly helpful in preventing infection in burn wounds.

iodopor

compound of idodine complexed with an organic molecule, increasing iodines stability and efficiancy

sepsis

condition of contamination

detergents

contain synthetic surfactant molecules with both polar and nonpolar regions that have strong cleansing activity but are more soluble, even in hard water

asepsis

contaminate free state

alcohols

denature proteins and disrupt membranes; can be a disinfectant or antiseptic

Sporicide

destroys endospores

bisphenol hexachlorophene

disinfectant; active ingredient in pHisoHex, a topical cleansing detergent widely used for handwashing in hospitals; effective against gram-positive bacteria such as Staphylococcal and Streptococcal skin infections

semi critical items

do not need sterilization, but a high level of disinfection; may contact mucous membranes or non-intact skin

simple desiccation

drying; inhibits metabolism; dried fruits, jerky

ideal disinfectant characteristics

effective against broad range of microbes, effective at high dilutions and in the presence of organic material, nontoxic, stable, non-offensive odor, soluble, inexpensive, sporicidal

benzalkonium chloride

example of quat that can be found in mouth washes and hand sanitizers

roccal

example of quat that requires 10 minutes to be effective, but kills a variety of microbes, but not Pseudomonas, which can break it down and use it for nutrients

GI endoscopes

example of semi critical items

surgical instruments,catheters, IV fluid

examples of critical items

bed linens, stethoscopes, blood pressure cuffs

examples of noncritical items

sonication

exposure to ultrasonic waves; cavitation (formation of empty space) disrupts cells, lysing them; laboratory research to lyse cells; cleaning jewelry, lenses, and equipment

nonionizing radiation

exposure to ultraviolet light; introduces thymine dimers, leading to mutations; surface sterilization of laboratory materials, water purification

ionizing radiation

exposure to x-rays or gamma rays; alters molecular structures, introduces double-strand breaks into DNA; sterilization of spices and heat-sensitive laboratory and medical items; used for food sterilization in Europe but not widely accepted in US

Triclosan

found in antibacterial soaps, Colgate and many plastics

zinc chloride

found in mouthwash

zinc oxide

found in topical antiseptic creams such as calamine lotion, diaper ointments, baby powder, and dandruff shampoo

Cryptosporidium

fungus that has a protective outer shell that makes it resistant to chlorinated disinfectants

surfactants

group of chemical compounds that lower the surface tension of water, major ingredients in soaps and detergents

Fluorine

has antimicrobial properties that contribute tot he prevention of dental caries

oligodynamic activity

highly effective at super low concentrations

Viricide

inactivates viruses

disinfection

inactivation of microbes on a surface of a fomite

fomites

inanimate objects that can carry and transmit disease

cationic detergents

include quaternary ammonium salts (quats) which can cause cytolysis

Bacteriostatic

inhibits bacterial growth

tincture

iodine solution in aqueous alcohol

heavy metals

kill microbes by binding to proteins, causing them to denature, and inhibiting enzyme activity

Algicide

kills algae

Bactericide

kills bacteria

Fungicide

kills fungi

antimicrobial agent

kills or inhibits microbial growth

-STATIC

means inhibits the growth

-CIDE

means it kills

ethyl and isopropanol

most commonly used alcohol, effecive against baceria, fungi and eveloped viruses

critical items

must be sterile because they will be used inside the body, penetrating tissues or the blood stream

hydrogen peroxide

not a good antiseptic because of the presence of catalase

silver

often combined with antibiotics, making antibiotics thousands of times more effective and can be incorporated into catheters and bandages

Semmelweis

one of first surgeons to implement handwashing

mycobacterium spp

organisms that are hard to kill because of its very effective mycolic acid barrier; phenolics are effective against

Iodine

oxidizing cellular components, including sulfur-containing amino acids, nucleotides, fatty acids and destabilizing the macromolecules that contain these.

Clostridium botuinum

produces a neurotoxin that causes botulism

lyophylization

rapid freezing under vacuum; inhibits metabolism; preservation of food, laboratory cultures, or reagents

degerming

removing microbes from a limited area

soaps

salts of long chain fatty acids with polar and nonpolar regions; main degerming action is to mechanically carry away the microbes

Filtration

size selection

argyria

skin turns irreversibly blue grey

phenolics

stable, persistent on surfaces, less toxic than phenol, inhibit microbial growth by denaturing proteins and disrupting membranes

peroxide

strong oxidizing agents that can be used as disinfectants or antiseptics, widely used is hydrogen peroxide

aseptic techniques

techniques or methods that maintain the sterile condition of products

Lister

treated wounds with carbolic acid...led to lower infection rates

Alcohol and hydrogen peroxid

two commonly used antiseptics

sterilization, disinfection, antisepsis, sanitization

types of degerming

HEPA filtration

use of high-efficiency particulate air filter with .3 um pore size; physically removes microbes from air; laboratory biological safety cabinets, operation rooms, isolation units, heating and air conditioning systems, vacuum cleaners

Membrane filtration

use of membrane filter with .2um or small pore size; physically removes microbes from liquid solutions; removal of bacteria form heat-sensitive solutions like vitamins, antibiotics, and a media with heat-sensitivie components

copper sulfate

used as an algicide in swimming poos and fish tanks

disinfectant

uses chemical or physical means of removing microbes from nonliving objects; should be fast acting, stable, easy to prepare, inexpensive, easy to use

autoclave

uses heat and pressure to sterilize items (denatures proteins)

Incineration

very high temperatures to destroy all microorganisms

chlorine

when mixed with water, produces strong oxidant called hypchlorous acid, which destroys all types of molecules by breaking bonds