Chapter 11 -- Physical & Chemical Agents for Microbial Control Flashcards
Simmelweis
Reduced childbirth fever - washing hands in chlorinated lime
Lister
aseptic technique in surgery - phenol to clean
Pasteur
aseptic technique in lab
Sterilization
removing ALL living organisms, or organisms that can become living (endospores), from a surface – sterile is ABSOLUTE
Disinfectant
destruction of vegetative pathogens on inanimate objects
Antiseptic
chemicals applied to body surfaces to destroy or inhibit vegetative pathogens
Decontamination
destruction, removal, reduction in number of undesirable microbes – only gets rid of some bacteria
Degermination
cleansing technique that removes microbes and debris from living tissue – washing hands, showering
Sanitization
cleansing technique that removes microbes and debris from inanimate objects – relies on a standard set by government (health department)
Sepsis
contamination
Asepsis
without contamination
Heat
preferred agent of sterilization for all materials not damaged by it
Thermal Death Point (TDP)
lowest temperature at which all microbes in suspension killed in 10 minutes
Thermal Death Time (TDT)
minimum time required to kill all microbes in liquid at GIVEN temperature
Decimal Reduction Time (DRT, D value)
time required to kill 90% of microbes population at a given temperature – D50=1min, where 50 stands for degree of temp
MOIST heat
Mode of Action: denaturation of proteins, Time to Act: penetrates quickly – happens quickly (hydrolysis) – i.e. boiling, autoclave, pasteurization
Boiling
100 degrees Celsius, 212 degrees Fahrenheit – Destroys most vegetative cells of bacteria and fungi (30 minutes) ; inactivates some viruses
Autoclave
Pressure: 15 psi; Temperature: 121 degrees Celsius; Time: 15 to 20 minutes; Effectiveness: all vegetative organisms, endospores, disrupts nucleic acid structure of viruses – Limitations: penetration required, materials need to be heat resistant, prions require 134 degrees Celcius and 30 psi
Pasteurization
process that kills most pathogens and lowers bacteria count that food won’t spoil rapidly at refrigerator temps – Equivalent Methods: Flash Methods – 72 degrees Celsius, 15 seconds, continuous ; Holding Method: 63 degrees Celsius, 30 minutes, classic method, batch method
UHT
Ultra High Temp Processing – 74 degrees Celsius —> 134 degrees Celsius —> 74 degrees Celsius all in less than 5 seconds
Dry Heat
Mode of Action: oxidation; Time to Act: penetrates slowly – i.e. flaming, incineration and hot air oven
Direct Flaming
bunsen burner flame up to 1800 degrees Celsius
Incineration
infrared incinerators (up to 800 degrees Celsius); furnace (up to 6500 degrees Celsius)
Hot Air Oven
170 degrees Celsius x 2 hours (150 - 180 degrees Celsius for 2-4 hours)
Non-ionizing radiation
UV rays, non penetrating; Mode of Action: damages DNA by causing formation of bonds between adjacent pyrimidine bases (usually T dimers) – 1-380 nm; below 260 nm best; sunlight > 295nm -380nm
Ionizing radiation
Gamma rays; less than 1nm – penetrating – mode of action: dislodge electrons from atoms, create ions
Refrigeration
‘static
Freezing
‘static – flash freezing doesn’t create as many crystals in cells so it tastes better
Desiccation
dehydrator (drying out) and osmotic pressure (plasmolysis)
Filtration
seperation of organisms from liquid or air, can be reliable sterilization if done well – AIR: HEPA filters (removes >0.3um); LIQUID: pore size is critical (0.01um for sterility)
Lyophilization
freeze-drying; culture preservation method
Phenol coefficient
former standard for evaluating effectiveness of chemical agents
Zone of inhibition
positive sensitivity test; clear area without growth around disc
USE DILUTION TEST
currents standard, the chemical that kills at lowest dilution is considered most effective
(MIC) Minimum inhibitory concentration
is the lowest concentration of an antimicrobial that will inhibit growth after overnight incubation
Chlorohexidene
an alternative to hexachlorophene that is not absorbed by skin and just as effective; contains chlorine & 2 phenolic rings
Triclosan
in antimicrobial soap
Alcohol
colorless hydrocarbons with one or more -OH groups; MODE: protein denaturation, ‘cidal, fast acting, evaporates, no residue; coagulates protein layer – concentration: 60-95%; optimum 70%
Aldehydes
organic substances with -CHO on the terminal carbon; MODE: protein denaturation
glutaraldehyde
rapid, broad spectrum; sterilizing agent; kills endospores in 3 hours; 2% solution CIDEX is sporicidal in 3-10 hours
Heavy metals
denature proteins by binding to functional groups of protein & inactivating them – very toxic to humans – biologicals fluids neutralize their actions
Oligodynamic action
property of having antimicrobial effects in exceedingly small amounts
Biocides
kills living cells
Ethylene Oxide
MODE: reacts vigorously with functional groups of proteins and DNA – sterilize in closed chambers without heat; sporicidal if used correctly - slow acting (90min-3 hours) mattresses (14 hours); explosive & carcinogenic
Phenolics
phenol derivatives; disrupts membrances – consists of one or more aromatic carbon rings with added functional groups
Cresol
Lysol - an alkylated phenol
Formaldehyde
sharp, irritating gas, readily dissolves in water; 37% aqueous solution = formalin; carcinogen
Ortho-phthalaldehyde
stable, non irritating, similar action to glutaraldehyde but faster acting; disadvantage: inability to reliably destroy endospores & stains proteins on human skin
Halogens
nonmetallic elments that share similar chemical properties; MODE: oxidizing agent in ABSENSE of organic matter – microbe death occurs in 30 minutes, endospores require several hours, photosensitive
Chlorine
halogen; compounds combine with water to form strong oxidizing agent
Iodine
halogen; MODE: inhibits protein function; oxidation
Surfactants
MODE: decrease surface tension among molecules of a liquid; dissolve lipids; disrupts membrane, denature proteins
Soaps & detergents
sufactants; mechanical removal
Anionic detergents
surfactants; sanitizers (dairy, food)
Cationic detergents
surfactants; more effective die to amphipathic nature
QUATS
antiseptic for mouth, skin or rubber – effective reduced in presense of organic matter; require alkaline pH, doesn’t work on Tb, Hepatitis, endospores. Pseudomonas actively grows in QUATS
O-Zone
peroxygens; 03; has killing power but not long lasting
Hydrogen peroxide
peroxygens; colorless, caustic liquid that decomposes in present of light, metals or catalase – ineffective on opens wounds; sporicidal at high temps
Catalase
enzyme that breaks down hydrogen peroxide immediatly
Peracetic acid
most effective liquid chemical sterilizer; effective in 5-30 minutes - no toxic residue
Dyes
used in staining procedures and in selective and differential media; MODE: interfere with replication, block cell wall synthesis
Aniline dyes
crystal violet and malachite green – effective against gram positive bacteria and various fungi - used in solutions and ointments to treat skin infection
Acridine
antisepsis and wound treatment in medical and veterinary clinics
Carbol fuchsin
a phenolic
Plant Oils
THYMOL: thyme – presevative; EUGENOL: cloves – disinfect cavities
