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21 Cards in this Set
- Front
- Back
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Microbiological contaminants
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unwanted microbes present in or on a substance
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Microbial survival
highest resistance moderate resistance least resistance |
highest resistance, prions, bacterial endospores
moderate resistance Pseudomonas, mycobacterium TB, S, aureus protozoan cysts least resistance most bacterial vegetative cells fungal spores and hyphae yeast enveloped viruses protozoan trophozoites |
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microbicidal
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permanent loss of reproductive capacity
agents are microbicidal |
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death rate depends on
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number microbes
nature of microbes in population temperature, pH concentration of dosage of agent presence of solvents, organic matter, inhibitors |
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modes of action
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cell wall becomes fragile, cell lyses
cell membrane loses integrity protein and nucleic acid synthesis prevent replication, transcription, translation, peptide bond formation proteins disrupt of denature proteins |
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physical control methods
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heat moist and dry
cold temperatures desiccation radiation filtration |
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moist heat
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lower temperature, least exposure time
autoclave most effective form of heat microbial control steam under pressure sterilization steam must reach surface of item being sterilized item must not be heat or moisture sensitive denaturation of proteins, destruction of membranes and DNA |
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Thermal death time (TDT)
Thermal death point |
shortest length of time required to kill all test microbes at specified temperature
lowest temperature required to kill all microbes in sample in 10 minutes |
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boiling
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100 C 30 minutes disinfectant
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Pasteurization
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heat applied to beverage kill potential agents of infection and spoilage without destroying the food flavor
kills non-spore-forming pathogens, does not kill endospores, or many non pathogenic microbes |
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dry heat
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must use higher temp then moist heat
incineration flame -electric heating ignites reduces microbes |
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Refrigeration
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Microbiostatic slows growth of microbes
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dessication
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gradual removal of water from cells
leads to metabolic inhibition not effective microbial control many cells retain ability to grow when water reintroduced |
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lyophilization
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freeze drying, preservative
safer transport of infectious agents |
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ionizing radiation
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breaks DNA sterilize medical supplies and products
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non-ionizing radiation
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minimal penetrating power
UV light creates thymine dimers |
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filtration
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hepa most common air filters
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decontamination level
high-level intermediate -level low-level |
high level germicides, kill endospores used for devices in sterile environments (body tissue)
intermediate level kill fungal spores ( not endoscopes) tubercle bacillus, virus low level eliminate only vegetative bacteria, fungal cells, |
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phenolics
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disrupt cell walls, membranes and precipitate proteins
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hydrogen peroxide
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produce highly reactive hydroxyl-free radials that damage protein and DNA while decomposing to 02 gas toxic to anaerobes
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detergents, soaps
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mechanically remove soil and grease containing microbes
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