The control of microorganism Flashcards
what is autolysis
Cell death linked to activation of lytic enzymes
what is the definition of microbial death
The permanent loss of reproductive ability under ideal environmental conditions
what is the d value?
decimal reduction time – time required to reduce the viable population by a factor of 10
what is a Antimicrobial agent
natural or synthetic chemical that kills or inhibits growth of microorganisms
what does Bacteriostatic mean
inhibits bacterial growth
what does Bacteriocidal mean
kills cells, but no lysis or cell rupture
what does Bacteriolytic mean?
induces killing by lysis releasing cytoplasmic contents
Ways that agents kill or inhibit microbes
Alteration of membrane permeability
Damage to nucleic acids
Damage to proteins
what does Sterilisation mean
: Destruction of all microbes & viruses from an object. Sterile = absence of all viable organisms
what does disinfection mean
Destruction of most microbes & viruses on non-living surfaces (inanimate objects)
what does Antisepsis mean
Reduction in number of microbes & viruses (particularly pathogens) on living tissue
what does antimicrobial drugs
Destroy microorganisms within the body
what does sanitation mean
Removal of pathogens from objects in order to meet public health standards
what was some psyhical microbial control methods
Heat (dry or moist)
Radiation (ionising & UV)
Filtration (removal)
Physical – heat sterilisation
Macromolecules lose structure & function (denature) at very high temperature
Thermal death time: the time it takes to kill all cells at a given temperature
Thermal death point: the lowest temperature required to kill all cells in 10 min
heat sterlisation example
dry heat: incineration, flaming, hot air ovens
Moist heat: boiling or steam under pressure (autoclave). Better penetrating power than dry heat
Pasteurisation: use of heat to reduce the number of disease-producing microorganisms in food & drinks
Unlike the use of chemicals, no toxic residue remains when heat sterilisation is completed
what is an autoclave
Moist heat
Sealed chamber
Kills all microbes & endospores
what is Pasteurisation
Heat process designed to reduce microbial load in heat sensitive liquids
radiation sterlisation?
effective way to sterilise or reduce the microbial burden in almost any substance
what are the Two types of electromagnetic radiation
Non-ionising, Ionising
what is non ionsing radiation
useful for decontaminating surfaces & materials that do not absorb light (e.g. air & water)
what is ionoing radiation
necessary to penetrate & decontaminate solid or light-absorbing materials (effective for sterilising food products & medical supplies)
what is the purpose of filter sterllisation
removal of viable cells
what is filter sterisation used to sterlise
`thermolabile (heat-sensitive) materials (drugs, vitamins, proteins)
air or gases (e.g. HEPA filters)
