MicroLecE2Ch7 Flashcards
Sepsis
Microbial contamination
Asepsis
Absence of significant contamination
Sterilization
Removing all microbial life, including prions and spores
Commercial Sterilization
Killing C. Botulinum endospores
Disinfection
Removing pathogens
Usually referring to non-living things or inanimate objects
Antisepsis
Removing pathogens from living tissue
Degerming
Removing microbes from a limited area
Sanitization
Lowering microbial counts on eating utensils
Biocide/Germicide
Kills microbes
Bacteriostasis
Inhibiting, not killing, microbes
What is efficacy of treatment dependent on?
1) Number of microbes: larger the population of bacteria, longer time it takes and more difficult it is to kill
2) Environment: some types of environment can inhibit sterilization
3) Time of exposure
4) Microbial characteristics: does it have a capsule, is it a bacteria or a virus
5) Microbial death curve: effect of high or low initial load of microbes
What are the actions of Microbial agents?
1) Alteration of membrane permeability (disruption to membrane)
2) Damage to proteins (denaturing of proteins)
3) Damage to nucleic acids
Physical Methods of Control
1) Heat
2) Filtration
3) Low Temperature: inhibits microbial growth but does not kill it. So cold bacteria cannot reproduce
4) High Pressure: denatures proteins
Pro: sterilization
Con: thing must be able to w/stand high pressure
5) Desiccation: prevents metabolism; bacteriostatic
6) Osmotic Pressure: causes plasmolysis
Thermal Death Point (TDP)
Lowest temp at which all cells in a culture are killed in 10 minutes (variable is temp)
Thermal Death Time (TDT)
Time during which all cells in a culture are killed at a specific temp (variable is length of time)
Autoclave
Giant box w/a pressure jacket
Anything put in it for 15 minutes @ 121 C will be sterilized. Uses moist steam, which is at a higher temp.
Pros: full sterilization
Cons: whatever put it in must withstand the heat and steam
Pasteurization
Reduces spoilage organisms and pathogens
Used on food which cannot be autoclaved
Applied at high heats but for very short time (flash heat)
Pros: can treat food and other things that cannot withstand autoclave without ruining them
Cons: cannot sterilize fully like an autoclave can
Dry Heat
Kills by oxidation (such as in an oven)
Pros: one of few heat methods where there’s no moisture so it can be used on things that cannot get wet
Cons: takes a long time for sterilization 2 hours @ 170 C
Filtration
Liquid is passed through a filter with tiny pores that do not allow microbes to pass through
Pros: can achieve sterilization if done correctly; does not use heat or pressure
Cons: only used w/liquids; doesn’t always achieve full sterilization
Radiation
1) Ionizing: X-rays, gamma rays, electron beams
Pros: does not damage something, can penetrate further than UV/Non-ionizing, works for something that cannot w/stand heat and moisture
Cons: doesn’t sterilize, doesn’t travel through or deep into liquid, plastic, glass
2) Non-ionizing: UV
Pros: doesn’t cause damage to thing
Cons: doesn’t sterilize, doesn’t travel through or deep into liquid, plastic, glass
What factors is effective disinfection dependent on?
1) concentration of disinfectant: high3er concentration doesn’t necessarily mean more disinfecting
2) Organic matter
3) Environmental pH
4) Time disinfectant was left on
Use-Dilution Test
Determines efficacy of a disinfectant
Metal rings dipped in test bacteria are dried and then placed in disinfectant. Rings are transferred to culture media to see whether anything grows/bacteria survived treatment
Disk-Diffusion Method
Disk soaked in a chemical disinfectant is put on a plage of bacteria, incubated, and then the zone of inhibition is measured
Chemical Classes
1) Alcohols
2) Aldehydes
3) Biguanides
4) Chemical Food Preservatives
5) Gaseous Sterilants
6) Halogens
7) Heavy Metals
8) Peroxygens
9) Phenols
10) Quats
11) Surfactants
12) Supercritical Fluids
Alcohols
Denatures proteins, dissolves lipids Requires water Higher concentration not more effective Pro: does not damage skin or tissue Exs: ethanol, isopropanol
Aldehydes
Inactivate proteins by cross-linking w/functional groups
Used in medical equipment
Ex: formaldehyde – used to preserve human tissue b/c it is a complete sterilant
Biguanides
Disrupt plasma membrane
Ex: Chlorhexidine
Chemical Food Preservatives
Organic acids inhibit metabolism – bacteriostatic
Control molds and bacteria in foods and cosmetics
Exs: sorbic acid, benzoic acid
Gaseous Sterilants
Chemicals that have been pushed higher than their boiling points to the gas state
Denatures proteins
Pros full sterilization, does not damage
Cons: gas so you cannot see, has sweet smell, can kill you if yu breathe in
Halogens
What they target to kill in the cell depends on the halogen
1) Iodine: alter protein synthesis and membranes. Tincture: in aqueous alcohol, Iodophor: in organic molecules
Pro: doesn’t harm tissue
2) Chlorine/Bleach: oxidizing agent, targets nucleic acids
Cons: corrosive
Heavy Metals
Very high antimicrobial properties
What they target to kill depends on what the metal is
Denatures proteins
Threading silver through mop heads and clothing used in hospitals
Peroxygens
Oxidizing agents
Used on contaminated surfaces
Exs: O3, H2O2, paracetic acid
Phenols
Disrupt plasma membranes
Pro: very effective
Cons: very corrosive, doesn’t sterilize
Ex: Triclosan
Quats
Positively charged polyatomic ions
Disrupts cell membrane
Used in food service sanitation
Surfactants
Molecules that have polarity
NO antimicrobial properties, just removes organic matter like dirt and grime taking bacteria with it
Does not sterilize or sanitize
Exs: Soap, Acid-anionic detergents, Quarternary ammonium compounds
Supercritical Fluids
Molecules that have unique characteristics, not quite in gaseous form but not quite in liquid form
Microbial Characteristics
Most Resistant to Least Resistant:
Prions: amino acid sequence itself must be destroyed. Takes either extreme heat or very high levels of chemicals
Endospores of bacteria: resistant to desiccation, heat, chemicals
Gram-negative bacteria: has 2 membranes
Viruses w/out envelopes
Gram-positive bacteria: has 1 membrane
Viruses w/lipid envelopes
