Ch 11 - Microbial control: agents (study guide)

Be familiar with all the terms and their definitions (table 11.2)

Decontamination

Definition: The destruction, removal, or reduction in number of undesirable microbes; overall term

Example: Asepsis, disinfection, sanitization, degermation, sterilization

Sepsis

Definition: The growth of microorganisms in the tissues

Example:The presence of infected wounds, blood infection

Asepsis

Definition: Techniques that prevent the entry of microorganisms into sterile tissues

Example: Cleansing the skin with iodine prior to surgery, using sterile needles

Antiseptic

Definition: Chemicals applied to body surfaces to destroy or inhibit vegetative pathogens

Example: lodophors, antibacterial soap, chlorhexidine

Disinfection

Definition: Destruction of vegetative pathogens on inanimate objects

Example: 5% bleach, boiling water

Sanitization

Definition: Cleansing technique that removes microorganisms and debris from inanimate surfaces

Example:Dishwashing, laundering clothes

Degermation

Definition:Cleansing technique that removes microorganisms and debris from living tissue

Example: Surgical handscrub, alcohol wipes

Sterilization

Definition:The removal or destruction of all viable microbes

Example: Autoclaving, ionizing radiation (correctly applied)

Microbial Death

• Prevents reproduction capabilities or outright kills the microbe. Caused by:

  • Heat

Heat

Denature the envelope/membrane/enzymes

Heat is important

• Metal, etc better than plastic since sterilization by heat

• Heat is moist and dry (Autoclave or Pasteurize vs Bensen Burner)

Moist heat

 lower temperatures and shorter exposure time; coagulates and denatures proteins, halting metabolism

Dry heat

Dehydrates, Incinerates, kills microbes, removes water, denatures protein. Remove water from the bio system, the system stops.

Cold

Microbistatic

Filtration

Comes into play when you cannot use an autoclave like plastic that gets altered by heat you sterilize the media with filtration

Desiccation

Removal of water inhibits metabolism and growth Freeze-drying (lyophilization) preserves cultures and foods. Microbes resume growth when water returns.

Radiation – Ionizing

 Deep penetration breaks DNA strands (phosphodiester backbone). Gamma rays, X-rays, cathode rays. Used for medical devices and food sterilization.

Gamma radiation

sterilizes plastics BUT doesn’t destroy it; easier + quicker than other sterilants 

Radiation – Nonionizing UV

Creates thymine dimers in DNA, blocking replication/transcription. UV lamps for surfaces, air, water. Limited penetration; sterilizes surfaces and transparent fluids.

Population & Nature

Population too small to reproduce, population too big to sustain on nutrients in the environment, opposing populations, self-destructive nature, etc.

Agent dosage and concentration

Using chemical agents to destroy or limit growth

Autoclave

•  Heat and Pressure. Works at 15 psi/ 121 degrees c /10-40min. Pressure increases the temperature of the steam. The steam has to make contact with the surface of the desired item, and the item cannot be moisture sensitive, like plastic.

Denatures proteins, membranes, and DNA. Decontaminates cultures.. CAN KILL ENDOSPORES

Tyndallization

Unpressurized steam

• Arnold's Sterilizer puts the items of interest at 100°C for 30 minutes over 3 days. Items are incubated between cycles to allow endospores to germinate.

• This is used for media or foods that cannot be autoclaved and can disinfect but not sterilize medical supplies

Pasteurization

- heat (disinfection), kills non-spore-forming pathogens (lowers microbe count) without ruining food flavour/value (doesn’t kill endospores or nonpathogenic microbes) (63ºC, 30 Min)

Flash

• This method works at 71.6°C for 15 seconds, using “ultrahigh temperatures.” Objects are put at 134°C for a few seconds.

• This is used for the disinfection of milk and dairy products to destroy milk-borne pathogens. Ultra-high temperatures sterilize products, increasing shelf life. Applied to many liquid products like beers, juices, wines etc. .

Ultra

• is a heat treatment that operates at higher temperatures than traditional pasteurization, but below the extreme conditions of UHT sterilization. It is designed to kill nearly all microorganisms that cause spoilage and disease, significantly extending the product’s shelf life.

• 125–138°C (257–280°F) to 2-4 seconds

is pasteurization a form of disinfection or sterilization

form of disinfection, not sterilization. It involves applying moderate heat to a liquid or food product in order to kill most pathogenic microorganisms that can cause disease or spoilage. However, pasteurization does not destroy all microorganisms, particularly bacterial spores, which are heat-resistant.

main goal of pasteurization

 make food safe for consumption and to extend its shelf life without significantly altering its flavor, texture, or nutritional value.

Can Boiling water remove (chemicals, toxins, or bacterial spores), counts as disinfections, kills or inactivates all pathogens that cannot form spores (viruses, bacteria, protozoa)

no

boiling water effects

• This uses a water bath or is pan heated to 100°C. The disinfected items are placed in water for 30 minutes to kill vegetative pathogens.

• This method is limited to the disinfection and sanitization of heat-resistant household objects such as eating utensils, clothing, sick room supplies, baby supplies, bedding, and water in emergencies. If things are not fully disinfected and reinfected, they could create super infections.

Microbicidal

kills microbes

Microbistatic

slows/reduces load of microbes & allows the host’s immune system to kill microbes

Ionizing radiation

• gamma, beta, & alpha waves; breaks down phosphodiester bonds of DNA/RNA

  • Very dangerous; cannot be stopped by barriers (unless it’s thick Pb)

Nonionizing radiation

• forms thymine dimers & shortens polypeptides

  • Little penetrating power + interferes w/ replication 

  • May be stopped by barrier

Thymine dimers

• in DNA, if there are 2 thymine bases adjacent to each other, they will get an extra bond & blocks DNA polymerase, causing transcription to not fully occur

  • Formed by UV radiation/ionizing radiation

RECALL: thymine is only found in DNA

Halogens

• Used for water - 

1. Chlorine: hypochlorites, chloramines (intermediate level, denaturates proteins, unstable in sunlight)

2. Iodine: Iodophors (betadine - interferes with disulfide bonds of proteins, intermediate level ex. disinfectants)

Phenols

Carbolic acid, acrid poisonous compound ( Disrupts cells walls + membranes + precipitate proteins)- low to intermediate level (bacterial, fungicidal, virucidal [not sporicidal])

Alcohols

Only ethyl and isopropyl are suitable for microbial level (Concentrations of 50% and higher needed, dissolves membrane lipids, coagulates proteins of vegetative bacterial cells and fungi) Kills better at 70% than at 100%

Detergents

Polar molecules, surfactant (quaternary ammonia compounds, act as surfactants, alters membrane permeability of bacteria and fungi, very low level)

Soaps

Alkaline compounds, removes soil and grease containing microbes, weak microbicides, destroys sensitive forms like gonorrhea, meningitis, syphilis

Heavy metals

binds to catalytic sites:

Hydrogen peroxide

Antiseptic at low concentrations, strong solutions are sporicidal (Produces hydroxyl-free radicals, damages proteins and dna, decomposing to O2 gas - toxic to anaerobes)

Surfactants

 substance similar to phospholipids & embeds itself into the cell membrane; once it does, breaks down cell membrane

Iodine (action)

• This compound is used since it denatures proteins and is used in surgeries before scalping somebody. 

• Orange material is Betadine

• Iodine is toxic at high levels but iodophor is an organic compound that is conjugated to iodine

• Oxidizing agent that penetrates cell membrane, disrupts protein and nucleic acid structure. Used as a topical anesthetic (kills bacteria, viruses, fungus)

Chlorine (action)

• Halogens: Used to disinfect water

• Chlorine is used to sterilize water and interacts with sunlight which breaks down over time

• What they do in san jose water is they put Chloramines instead of Chlorine (NH2Cl)

• Oxidizing agent that denatures proteins  disrupts cell membranes, disinfects water and surfaces, (used in sodium hypochlorite (bleach) wide range effectibility.)

Alcohols (action)

• Only ethyl and isopropyl are suitable for microbial control

• Remember: All alcohols need water to react

• Denature proteins, dissolve lipids in microbial cell membrane causing cell death. Alcohols are effective against bacteria and viruses but less against spores

Mercurials (action)

Compounds containing mercury that act as biocidal agents, they denature proteins and inhibit enzymes, limited use due to toxicity concerns

Soaps (action)

 Surfactants that lower surface tension to remove dirt and microbes. They suspend oils and dirt which is then washed away

Phenols (action)

• Used by semmelweis and lister

• Poisonous compound that damages our cells but definitely damages microbes

• Does not kill sporophytes

• Lysol is a great phenol used in pipes

• Toxicity of phenolics makes them a questionable choice as antiseptics

• Organic compounds that can denature proteins nad disrupt cell membranes. Inactivates enzymes causing death, strong disinfectants

lyophilization

Freeze drying. Sucks the moisture out of the item by freeze drying it in a vacuum. Water immediately evaporated. Think about the potatoes in The Martian