Limiting Microbial Growth Flashcards
what is a D value
decimal reduction time
- time it takes to reduce the number of survivors 10 fold (log10) HAS TO BE A SEMI LOG SCALE GRAPH THO
sterilization
ALL cells, spores and viruses are destroyed
disinfection
substantial reduction of harmful microbes from surfaces (inanimate objects)
antisepsis
substantial reduction of harmful microbes from living tissue
biocide vs biostatic
biocide - kills a biological agent
static - stops growth but does not kill
is there a biostatic for viruses ?
they dont grow/metabolize on their own they need a host, theres nothing to slow down without the host
what is pasteurization
- it is a physical _____
heating at 63 °C for 30 min or at 72 °C for 15 seconds - kills most bacteria that causes spoilage
*physical disinfection
what is boiling as a control method
- it is a physical _____
at 100 °C for 1-3 min kills most microbes
*physical disinfection
describe autoclaving and it is a physical ______
high pressure (15psi) and steam 121 °C for 15-30 min and kills all microbes and endospores
- used to sterilize glassware
- physical sterilization
what is oven sterilization and it is a physical ______
baking with dry heat at 170 °C for 2-4 hours, good for things that can’t withstand moisture
*physical sterilization
what is incineration and it is a physical ______
driest heat, used for wastes, temp must be very high
*physcial sterilizarion
what is flame sterilization
- used for metal instruments, alcohol may be used
what ways can u remove microbes from heat-labile (not good in heat) substances (3) and describe
- gamma radiation
= used on plastics
*physical sterilization - UV radiation
= can’t stand heat/liquid like electronics - physical disinfection
- filtration
= very fine strainer that catches larger cells even viruses
*mechanical sterilization
biosafety cabinets disinfect the workspace via ____
air filtration & HEPA filter
what are phenolics
chemical control agent
- disrupts cell membranes
- denatures proteins
describe use of alcohols as a chemical control agent
most widely used
*antiseptics
- denature proteins
- dissolve membrane lipids
why would 70% ethanol be more effective than 100% (2)
- water helps ethanol penetrate the cells
- slows down ethanols evaporation
describe use of halogens as a chemical control agent
group 17
- chlorine / iodine
- oxidize cell components
- bind to and denature proteins
*iodine can be used as an antiseptic
describe use of quaternary ammonium compounds (QACs) as a chemical control agent
- detergents (have hydrophilic and phobic components)
- disrupt membranes
- can denature proteins
describe use of aldehydes as a chemical control agent
highly reactive and effective
- react with and denature proteins
- react with and denature nucleic acids
describe use of sterilizing gases as a chemical control agent
often used on heat-labile materials like plastics
mechanism of action depends on the type of gas
what are the most resistant and least resistant microbes
most resistant - prions then endospores
least - viruses with lipid envelopes then gram + bacteria
