Control of Microbial Growth Flashcards
Why control microbial growth?
- To prevent spread of pathogens and disease in hospitals, nursing homes, medical offices, and homes
- Prevent food contamination and spoilage at home and elsewhere
- To prevent microbial degradation of material sin industry or in homes
Free of all viable organisms (by removal or killing)
Sterile
Process of killing or removing all microorganisms in a material or object including any spores
Sterilization
The process of decreasing the number of viable microorganisms on an inatimate object/surface to a level that presents a minimum possibility of disease transmission or contamination
Disinfectant
Disinfection of a living tissue
Antiseptic
Reduction of microbial population to levels deemed safe
Sanitation
Any physical or chemical agent that either kills microorganisms or inhibits their growth
-There are antibacterial, antiviral, antifungal, and antiprotozoal
Antimicrobial agent
Antimicrobial agent that kills microorganisms
-Could be bacteriocidal, viricidal, fungicidal
Microbiocidal
Antimicrobial agent that inhibits the growth of a microorganism
-Specifically could be bacteriostatic, viristatic, and fungistatic
Micobiostatic
Inability of microorganisms to reproduce
Death for microorganisms
Different antimicrobial agents can act in different ways to kill or inhibit
Mechanisms of death
Alternating the physical state of the cytoplasm damages…
Ribosomes
Inactivating enzymes–>
Destroys proteins in cells and viruses
Disrupting the cell membrane–>
- Alters cell membrane permeability
- Lyse cell membrane
- Affect transport
Disrupting cell wall–>
Cell lysis
Characteristics of microbial growth (3)
- Microorganisms are not killed instantly
- Population death usually occurs exponentially
- Measure of agents killing efficiency
The time it takes to kill 90% or organisms
Decimal Reduction Time
Cells that are viable but nonculturable, once they recover they may regain the ability to reproduce and cause infection
Persister Cells
Conditions influencing the Effectiveness of Antimicrobial Activity
- Population size
- Population Concentration
- Concentration or intensity of an Antimicrobial Agent
- Duration of exposure
- Local Environment
Effect of population size on Antimicrobial activity
Larger populations take longer to kill
Physical control methods (4)
- Heat
- Filtration
- Radiation
- Dessication
-Very effective, widely used, denatures proteins, nucleic acids and the cell membrane (termal lysis)
Heat
Characteristics of Moist heat
- Steam or hot water
- More effective than dry heat
- Destroys viruses, fungi, and bacteria
- Degrades nucleic acids, denatures proteins, and disrupts membranes
Characteristics of sub-boiling temperatures
- Mild heating to kill vegetative microbes
- Does not sterilize or kill endospores
- Disinfection
- Slows down microbial growth to allow food to last longer, used for materials that cannot be boiled
Characteristics of Phenolics
- Derieved from phenol
- Commonly used as lab or hospital disinfectants
- Denature proteins and disrupt cell membrane
- Long lasting
- Odorous and can cause skin irritation
Characteristics of Alcohols
- Denature proteins
- Lipid solvents
- Damage lipids in cell membrane and damage cell membrane
Characteristics of Halogens
- Any of 5 elements, fluorine, chlorine, bromine, iodine, and astatine
- Important antimicrobial agents
Characteristics of Iodine
- Skin antiseptic
- Oxidizes and denatures cell constituents and iodinates proteins
- At high concentrations it may kill spores
Iodine compound with an organic carrier, released slowly to minimize skin burns
Iodophore
Iodine dissolved in ethanol
Tincture
Characteristics of Chlorine
- Oxidizes cell constituents especially proteins
- Good for disinfection of water supplies
- Destroys vegetative bacteria and fungi
- Chlorine gas is sporicidal
Characteristics of heavy metals
- Ions of mercury, silver, arsenic zinc, and copper
- Effective but usually toxic
- When combined with inactive proteins it may also precipitate proteins
Characteristics of Soap and Detergents
- Emulsifying agents (amphipathic)
- Make nonpolar molecules (lipids) more water soluble
- Helps physically remove microorganisms from clothing
- Denature protein and damage cell membrane
Characteristics of Quaternary Ammonium compounds
- Amphipathic organic cleansing agents
- Antimicrobial activity
- Effective disinfectants
Characteristics of Aldehydes
- Sporocidal and can be used as chemical sterilents
- Combine with inactive nucleic acids and proteins
- Used to preserve animal material
Characteristics of Sterilizing Gases
- Used to sterilize heat sensitive materials
- Microbicidal and sporocidal
- Combine with inactive DNA and proteins
