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Unit 2: All Words
NoteStudied by 98 peopleChapter 30 - Revolution and Nationalism
NoteStudied by 34 peopleChapter Ten: Disorders Featuring Somatic Symptoms
NoteStudied by 9 peopleDeBruyne_7e_PPT_ch05
NoteStudied by 3 people2.6: polyatomic ions
NoteStudied by 265 peopleTheories of Personality: Introduction to Theories of Personality
NoteStudied by 41 people
Topic 8: Control of Microorganisms by Physical and Chemical Agents
- Sterilization: destruction or removal of ALL viable organisms; usually used on inanimate objects
- Disinfection: killing, inhibition, or removal of pathogenic, vegetative organisms
- Disinfectants: agents, usually chemical, used for disinfection; usually used on inanimate objects
- Chemotherapy: chemicals used internally to kill or inhibit growth of microorganisms within host tissues
- Sanitization: reduction of microbial population to levels deemed safe (based on public health standards)
- Antisepsis: prevention of infection of living tissue by microorganisms
- Antiseptics: chemical agents that kill or inhibit growth of microorganisms when applied to tissue
- Sepsis: microbial contamination
- Asepsis: absence of significant contamination
- Antimicrobial agents: agents that kill microorganisms or inhinit their growth
- -cidal/-cide: agents that kill
- Germicide: an agent that kills certain microorganisms
- Bactericide: an agent that kill bacteria; most do not kill endospores
- Viricide: an agent that inactivates virsuses
- Fungicide: an agent that kills fungi
- Sporicide: an agent that kills bacterial endospores or fungal spores
- -static: agents that inhibit growth
- Pattern of microbial death
- Microorganisms are not killed instantly
- Population death usually occurs exponentially
- Organisms can be in a viable but nonculturable (VBNC) conditon - may regain the ability to reproduce and cause infection
- Conditions influencing the effectiveness of antimicrobial agent activity
- Population size
- Larger populations take longer to kill than smaller populations
- Population composition
- Microorganisms differ markedly in their sensitivity to antimicrobial agents
- Concentration or intensity of an antimicrobial agent
- Higher concentrations or intensities kill more rapidly (not linear relationship)
- Duration of exposure
- Longer exposure = more organisms killed
- Temperature
- Higher temperatures usually increased amount of killing
- Local environment
- Factors (pH, viscosity, concentration of organic matter) can impact effectiveness
- Organisms in bioflims are physically altered and less susceptible to many antimicrobial agents
- Three main microbial control methods: physical, chemical, and mechanical removal methods
- Physical methods
- Heat
- Moist heat: kills microorganisms by coagulating (denaturing) their proteins, degrades nucleic acids, and disrupts membranes; more effective than dry heat
- Autoclave sterilization - 121 °C at twice atmospheric pressure
- Boiling: heat to 100 °C or more at sea level; kills vegetative forms of bacterial pathogens, most viruses, and fungi and their spores within 10 min or less.
- Hepatitis virus can survive up to 30 min of boiling
- Endospores can survive up to 20 hrs + of boiling
- Dry heat: kills by oxidation effects (ie bunsen burner)
- Direct flaming: used to sterlize inoculating loops and needles - heat metal until it has a red glow
- Incineration: effective way to sterlize disposable items (ex: paper cups, dressings) and biological waste
- Hot air sterlization: place objects in an oven
- Require 2 hrs at 170 °C for sterilization
- Dry heat transfers heat less effectively to a cooler body than moist heat
- Low temperatures
- Effect depends on microbe and treatment applied
- Refrigeration: temperatures from 0 - 7 °C; bacteriostatic effect; reduces metabolic rate of most microbes, they cannot reproduce or produce toxins for some
- Freezing: temperatures below 0 °C
- Flash freezing: does not kill most microbes
- Slow freezing: more harmful because ice crystals disrupt cell structure
- Most parasites are killed by a few days of freezing
- Filtration
- Reduces/removes microbial population or sterlizes solutions of heat-sensitive materials by removing microorganisms
- Used to reduce microbial populations in air
- Radiation
- Ionizing radiation: gamma rays, x rays, electron beams, or higher energy rays; have short wavelengths (less than 1 nm)
- Causes mutations in DNA
- Used to sterlize pharmaceuticals, disposable medical supplies, food
- Penetrates human tissues = may cause genetic mutation in humans
- Nonionizing radiation: ultraviolet light (UV); wavelength longer than 1nm
- Damages DNA by producing thymine dimers, which cause mutations
- Used to disinfect operating rooms, nurseries, cafeterias
- Disadvantages: damages skin and eyes; doesn’t penetrate paper, glass, and cloth
- Microwave radiation: wavelength ranges from 1 mm to 1 m
- May kill vegetative cells in moist food
- Solid foods are unevenly penetrated by microwaves
- Bacterial endospores are not damaged by microwave radiation because lack of water in the endospore
- Chemical methods
- Used to control microbes on body surfaces and inanimate objects; disinfectant substances do not sterlize, but reduce microbial population
- Qualities of a disinfectant
- Acts rapidly
- Attacks a wide range of microbes
- High penetrability
- Readily mixes with water
- Not hampered by organic material
- Does not stain, corrode or damage object being disinfected
- Does not damage body tissue
- Phenols and phenolics
- Phenol (carbolic acid) was first used by Lister as a disinfectant
- Rarely used today because it is a skin irritant and has strong odor; used in some throat sprays and lozenges
- Cresols: derived from coal tar (lysol)
- Biphenols (phsiohex): effective against gram + staphylococci and streptococci; used in nursies but excessive use in infants may cause neurological damage
- Destroy plasma membrane and denature proteins
- Advantages: stable, persist for long times after applied and remain active in the presence of organic compounds
- Alcohols
- Kill bacteria, fungi, but not endospores or naked viruses
- Act by denaturing proteins and disrupting cell membranes
- Evaporate, leaving no residue
- Used to mechanically wipe microbes off skin before injections or blood drawing
- Ethanol: drinking alcohol (optimum concentration 70%)
- Isopropanol: rubbing alcohol (better disinfectant than ethanol - cheaper and less volatile)
- Halogens
- “Bleach”
- Any of five elements: fluorine, chlorine, bromine, iodine, and astatine
- Iodine and chlorine are important antimicrobial agents
- Iodine: Oxidized cell constituents and iodinates proteins; at high concentrations may kill spores; skin antiseptic.
- Cons: skin damage, staining, and allergies
- Iodophor: iodine complexed with organic carrier
- Chlorine: oxidizes cell constutients; important in disinfection of water supplies and swimming pools; used in dairy and food industries; effective household disinfectant; destroys vegetative bacteria and fungi but not spores
- Can react with organic matter to form carcinogenic compounds (ammonia)
- Heavy metals
- Ions of sliver, mercury, arsenic, zinc, and copper
- Effective but usually toxic
- Arsenic use in the past
- Combine with and inactivate proteins; may also precipitate proteins
- Detergents
- Have antimicrobial activity and are effective disinfectants, disrupt cell wall
- Amphipathic: organic molecules with hydrophilic and hydrophobic ends
- Act as wetting agents and emulsifiers
- Cationic detergents are effective disinfectants that kill most bacteria by not Mycobacterium, tuberculosis, or endospores
- Safe and easy to use but inactivated by hard water and soap
- Disinfectants
- Aldehydes
- most effective antimicrobials; inactivate proteins
- Formaldehyde gas: commonly used as formalin to preserve biological specimens and inactivate viruses and bacteria in vaccines; irritates mucous membranes and has strong odor; used in mortuaries for embalming
- Hydrogen peroxide (peroxygens)
- Used as an antiseptic - toxic to cell; not good for open wounds because quickly broken down by catalase present in human cells; effective in disinfection of inanimate objects; used by food industry and to disinfect contact lenses
- Sterilizing gas
- Used to sterlize heat-sensitive materials
- Microbicidal and sporicidal
- Combine with and inactivate proteins
- Ethylene Oxide Sterilizer
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Explore Top NotesNoteStudied by 98 peopleNoteStudied by 34 peopleNoteStudied by 9 peopleNoteStudied by 3 peopleNoteStudied by 265 peopleNoteStudied by 41 people
Unit 2: All Words
NoteStudied by 98 peopleChapter 30 - Revolution and Nationalism
NoteStudied by 34 peopleChapter Ten: Disorders Featuring Somatic Symptoms
NoteStudied by 9 peopleDeBruyne_7e_PPT_ch05
NoteStudied by 3 people2.6: polyatomic ions
NoteStudied by 265 peopleTheories of Personality: Introduction to Theories of Personality
NoteStudied by 41 people