Chapter 9 - Chemical Methods of Microbial Control Flashcards
Antisepsis
reduction in the number of microbes + viruses on LIVING tissue
Aseptic
refers to an environment/procedure free of pathogenic contaminants
Disinfection
destruction of most microbes + viruses on NONliving tissues
Sanitation
removal of pathogens from objects to meet public health standards
-stasis / -static
suffixed indicating inhibition, but not complte destruction, or a type of microbe
-cide / -cidal
suffixes indicating destruction of a type of microbe
Sterilization
destruction of all microbes + viruses in/on an object
Degerming
removal of microbes by mechanical means
Action of Antimicrobial Agents
not marked
- alteration of cell walls + membranes
- nonenveloped viruses arre more tolerant of harsh conditions
- damage to proteins + nucleic acids
Microbes from most resistant to most susceptible
Prions Bacterial endospores Mycobacteria Cysts of protozoa Active stage protozoa gram-neg bacteria Fungi Nonenveloped virus gram-pos bacteria Enveloped virus
3 methods of killing microbes
physical (heat, uv, fridge, freeze)
chemical (iodine, clorox)
biological (antibiotics)
Effects of High Temp
Microbial Control
- breaks H bonds
- denatures proteins
- interferes w integrity of cytoplasmic membrane + cell wall
- disrupts structure + function of nucleic acids
Thermal Death Point
lowest temp that kills all cells in broth in 10 mins
Thermal Death Time
time to sterilize vol of liquid at set temp
Autoclaving
- pressure applied to boiling water prevents steam from escaping
- boiling temp increases as pressure increases
Autoclave conditions
121C, 15psi, 15 mins
Pasteurization
- not sterilization (bc heat tolerant microbes survive)
- used for milk, ice cream, yogurt, fruit juices
Pasteurization of milk
- batch method (145F for 30 mins)
- flash pasteurization (161F for 15 secs)
- ultrahigh-temp (UHT) pasteurization (191F for 1 sec, longest shelf life)
Fridge + Freeze
Microbial Control
not marked
- decrease metab, growth, + preproduction
- psychrophilic microbes can multiply in refrigerated foods
- fridge halts growth of most pathogens
- slow freezing is better than quick
Dessication
- Physical Method of Microbial Control
- drying INHIBITS growth bc removal of water
-static
Lyophilization
- Physical Methods of Microbial Control
- for long term storage
- freezes bacteria that prevents formation of damaging ice crystals
- not for sterilization
Ionizing Radiation
not marked
Physical Methods of Microbial Control
- wavelengths shorter than 1nanometer
- ejects electrons from atoms to create ions
- ions disrupt h bonding, oxidize double covalent, create hydroxide ions
- ELECTRON BEAMS
- GAMMA RAYS
NONionizing radiation
- Physical Methods of Microbial Control
- wavelengths greater than 1nm
- excited electrons make new covalent bonds (affects 3D structure of proteins/nucleic acids)
- UV light causes pyrimidine dimers in DNA
- suitable for disinfecting air, transparent fluids, + surfaces of objects
- UV light doesnt penetrate well
- excited electrons make new covalent bonds (affects 3D structure of proteins/nucleic acids)
Alcohol
- chem method of microbe control
- ANTISEPTIC + DISINFECTANT
- swabbing skin w 70% ethanol prior to injection (antiseptic)
- denatures proteins + disrupts cytoplasmic membranes
- more effective than soap in removing bacteria fr hands
Oxidizing Agents
- chem method of microbial control
- peroxides, ozone, + peracetic acid
- kill by oxidation of microbial enzymes
- high level ANTISEPTIC + DISINFECTANT
- hydrogen peroxide can disinfect + sterilize surfaces (not useful for wounds)
Effects of Dry Heat
Microbial Control
- used for materials that can’t be sterilized w moist heat
- denatures proteins + oxidizes metabolic + structural chemicals
- requires higher temp for longer time than moist heat
- incineration is ultimate means of sterilization
most effective mean of disinfecting air and water
UV light
Gaseous Agents
- chem microbial control
- • Microbicidal and sporicidal gases for sterilizing agents
