Ch.9 part 2 Flashcards
what is osmotic pressure in physical methods?
uses a hypertonic solution to remove water from cells, causing them to shrink and inhibiting microbial metabolism, as enzymes require water to function properly.
what is the physical methods of radiation
ionizing radiation
how does radiation control growth?
-Removes electrons
-Disrupts hydrogen bonds
-Creates hydroxyls
How does radiation kill microbes?
-Toxic oxygen compounds
-Denature DNA leading to mutations and death
describe gamma rays in radiation?
-Penetrates into material: hours to kills
-Kills microbes, larvae, eggs, cells of fruit/vegetables
-Prevents spoilage of fresh fruit/vegetables, meat, spices
how does non ionizing (UV) control growth?
-Causes new bonds to be made
-Thymine dimers
how does non ionizing (UV) kill microbes?
-Distorts DNA shape
- Becomes impossible to replicate or transcribe
chemical agents act to adversely affect
Cell walls
Plasma membrane
Proteins
DNA
Chemical Methods of Microbial Control effect can vary depending on
Temperature
Exposure time
pH, concentration, or freshness of chemical
Chemical Methods of Microbial Control destroys or inhibits
Enveloped virus, bacteria, fungus, protozoa
What can survive chemical methods?
Fungal spores, endospores, protozoan cysts
phenol and phenolics
Dr. Joseph Lister (1867) used phenol to reduce infections during surgery
what are Pros to phenol and phenolics
Denatures proteins
* Disrupts membranes
* Effective in vomit, pus, saliva, feces
* Remains active on surfaces for extended periods of time
* Commonly used in homes, hospitals, labs
what are cons of chemical methods of microbial control
smells
skin irritant
what are the pros of alcohol in chemical methods of microbial control
Denatures proteins
* Disrupts plasma membranes
* Kills bacteria, fungus, enveloped viruses
* More effective than soap
* Swabbing prior to injection removes most microbes
what are the cons of alcohol in chemical methods of microbial control
not effective on fungal spores, endospores
Why do we use 70% or 85%
solutions of alcohol?
-More effective at denatures membranes
-Desaturation needs water
what is Tincture
a solution of a medicinal substance dissolved in alcohol or a mixture of alcohol and water.
(works better together)
what is halogen in chemical methods of microbial control
Effective against bacteria and fungus, fungal spores, some endospores and cysts, many viruses
unfold and denature enzymes
what are the four very reactive nonmetallic elements
Iodine (Betadine)
Chlorine (Bleach)
Bromine
Fluorine (toothpaste)
describe iodine
-Used as a tincture
-Iodophore – slowly releases iodine, non- irritating
describe chlorine
effective disinfectant
treat drinking water, pools, etc
describe oxidizing agents
-Kills by oxidation of
microbial enzymes
-High level disinfectant and antiseptic
Describe Hydrogen peroxide
Disinfect and sterilize surfaces
- Kill aerobes and facultative anaerobes if concentration is high enough to overwhelm catalase enzymes
- Not useful for treating open wounds due to catalase
what is surfactant
surface active chemical
-reduces the surface tension of a solvent
why are examples of surfactant
soaps and detergents
describe soap and detergent surfactants?
soaps have hydrophilic and hydrophobic ends
-good determine agent, but not antimicrobial
Detergents are positively charged organic surfactant
What is the role of heavy metals in chemical microbial control?
Heavy metals, like silver and mercury, denature proteins and act as low-level bacteriostatic and fungistatic agents, stopping reproduction of microbes.
what are pros of gaseous agents
- Denature proteins & DNA by creating cross-links
- Used on hospitals and dental offices
- Microbiocidal and sporocidal
- Ethylene oxide – kills endospores
what are cons of gaseous agents
Hazardous
* Often highly explosive – has to be performed in sealed chamber
* Extremely poisonous
* Potentially carcinogenic
what are examples of lysosomes
human tears, saliva
what are enzymes
Antimicrobial enzymes act against microbes
digest peptidoglycan
what controls microbes in their environment
Lysozyme – reduces the number of bacteria in cheese
Prionzyme – remove prions on medical instruments
What are antimicrobials and how do they work?
Antimicrobials target cell walls, membranes, and protein synthesis to control microbes
