Control of Microorganisms Flashcards
sterilization
the killing or removal of all viable organisms including endospores
inhibitin
effectively limiting microbial growth
decontamination
the treatment of an object to make it safe to handle
disinfection
directly targets the removal of all **pathogens not necessarily all microorganisms
physical methods (examples)
heat
radiation
filtration
chemical methods (antimicrobials) (examples)
external surfaces: sterilants, disinfectants, antiseptics
internal: antibiotics, antivirals, antifungals
heat
- high temps *denature macromolecules
- decimal reduction time
- time necessary to kill a defined *fraction is independent of the initial cell concentration
decimal reduction time
D
amount of time required to reduce viability tenfold
inversely correlated with temp
-organism specific
thermal death time
time needed to kill all cells at a given temp
dependent on the population size of the microorganism
To compare a standardized number of starting cells is needed.
Endospores and heat
survive heat that would rapidly kill vegetative cells
-need higher temp
(resistant to boiling for a long time - 5 min for a decimal reduction ie 90% dead)
autoclave
sealed device that uses steam under pressure
- the high temp NOT pressure kills microbes
- the sterilization time is when the object being sterilized reaches 120C (NOT the autoclave itself)
Pasteurization
process of using precisely controlled heat to reduce the microbial load in heat-sensitive liquids.
- increases shelf life
- reduces pathogens
- flash pasteurization 72C for 15s
- bulk pasteurization 65C for 30 min
Radiation
causes modifications and breaks in DNA, inhibits replication, transcription and cuases death
- cannot penetrate solid, obaque surfaces
- used in disinfection of water or air
*Ionizing radiation
radiation that produces ions and other reactive molecules
- has a decimal reduction time
- sources of radiation: cathode ray tube, X-rays
- used for sterilization in the medical field and food industry
Filter sterilization
- avoids the use of heat on sensitive liquids or gas
- pores of filter are too small for organisms to pass through, so they are caught.
Depth filters
fibrous sheet or mate made from an array of fiber
*HEPA filters
Membrane filters
- like sieve
- nucleopore filter
- filtration speed can increase by syringe, pump, or vacuum
antimicrobial agents
bacteriostatic: inhibit growth of microorganism
bacteriocidal: kill microorganism
bacteriolytic: kill microorganism by inducing lysis
(Think about the associated graphs)