Sterilization
Destruction or removal of all viable organisms (surgical equipment)
Disinfection
Killing, Inhibition, or Removal of disease causing (pathogenic) organisms
- Disinfectants (usually used on inanimate objects)
Sanitation
Reduction of microbial population of lvls deemed safe (dishwasher)
Antisepsis
Prevention of infection of living tissue by
microorganisms
- antiseptics
- chemical agents that kill or inhibit
growth of microorganisms when applied
to tissue
- cleaning a wound
What is BioSafety Levels determined by?
Determined by:
- Agents Affectivity
- Ease of Transmission
- Potential Disease severity
- Type of work done with the agent
What are BSL-1 Agents?
- Dont cause infection in healthy human adults
- include noninfectious disease
What are BSL-2 Agents?
- pose moderate risk to laboratory workers and the community, and are typically “indigenous” (commonly found in that geographical area).
- these microbes are there anyway!
- however, cultivating these microbes increase their “biomass” and can pose a problem …Staphylococcus aureus and Salmonella spp., and
viruses like hepatitis, mumps, and measles
viruses
What are BSL-3 Agents?
- potential to cause lethal infections by inhalation
- either “indigenous” or “exotic,” meaning that they are derived from a foreign location
Mycobacterium tuberculosis, Bacillus anthracis,
West Nile virus, and human immunodeficiency
virus (HIV).
What are BSL-4 Agents?
- Most dangerous & Most Fatal.
- Typically exotic and easily transmitted by inhalation, cause infections for which there are no treatments or vaccinations
- only a small number of laboratories in the United States and around the
world appropriately equipped to work with these agents.Ebola virus and Marburg virus, both of which cause
hemorrhagic fevers, and smallpox virus
Why do we need to control microbial presence and growth and
- essential for treating/curing / preventing infectious diseases,
- controlling food contamination (rotting v.s. fermentation)
- Biotechnological production.
What does death depend on?
- Death is not instantaneous
- death rate depends on controlling techniques/agents
- Death rate depends on microbes
What is Decimal Reduction Time (DRT / D-Value)?
The amount of time it takes for a specific protocol to produce a one order -of-magnitude decrease in the number of organisms, or the death of 90% of the population.
What is Thermal Death Point (TDP)?
The lowest temp of a microorganism at which al microbes are killed in a 10 minute exposure
What is Thermal Death Time (TDT)?
The length of time needed to kill all microorganisms in a sample at a given temp.
What is incineration and dry oven?
Incineration and dry oven use dry heat and sterilization. Incineration us high destructive and nasty microbes.
What physical methods can be used to control microorganisms at Moist Heat?
- Boiling at 100C for various periods of times
- Steam (moist heat and sterilization)
- Autoclave (pressure cooker)
*Note: complete sterilization is not practical form many applications and may alter quality of product. *
Note: Boiling and Autoclave are not ideas ways bc methods may ruin consistency of other organoleptic (sensory) qualities o the food
What is Pasteurization?
- Form of microbial control for food that uses heat but does not render the food sterile.
- Kills pathogens and reduces # of spoilages, causing microbes while maintaining food quality.
- pasturized food is NOT STERILE, will eventually spoil
What physical methods can be used to control microorganisms at Low temps?
Cooling: (0-7 C)
- Cooling in fridges inhibits microbial metabolism. Certain labs cultures can be preserved by fridges for later use.
Freezing: (-20 C)
- May stop microbial growth, kill susceptible organisms (ice crystal formation). Halted bacterial growth, can restart in thawed foods, should be treated like fresh perishables.
Ultra-Freezing: (< -70C)
- Bacterial cultures and medical specimens requiring long-term storage/transport are often frozen at ultra low temps of -70 or lower). Adding glycerol to sample prevent formation of deadly ice.
What physical methods can be used to control microorganisms with Pressure?
works, not convenient.
- Desiccation (removal of moisture): Cells require water for metabolism & survival, drying controls microbial growth but might not kill all microbes, which may start to regrow when conditions are favorable
- “Water activity” can be lower w/o removing the water. Adding solutes to create high osmotic pressures.
What physical methods can be used to control microorganisms with Radiation?
Ionizing Radiation: including X-rays, gamma rays, and high energy electron beams. : can easily penetrate paper and plastic, therefore be used to sterilize many packaged materials
Non-ionizing radiation (UV light, 260nm.): does not penetrate packaging.
What physical methods can be used to control microorganisms with Filtration?
Air Filtration: High-efficiency particulate air (HEPA) filters, have effective pore size of 0.3 um, small enough to capture bacterial cells, endospores, and many viruses, as air passes through these filters, nearly sterilizing the air on the other side of the filter
Liquid Filtration: Membrane filters to remove microbes from liquid samples. Useful for removing bacteria from various types of heat-sensitive solutions.
Chemical: Phenolics
Molecule: Triclosan, Lysol
Mode of Action: Prot. Denaturation Membranes Disruption
Chemical: Metals
Molecule: Mercury
Mode of Action: Protein inhibition
Example: Topical
Chemical: Halogens
Molecule: Iodine, Chlorine (bleach), Fluorine (Toothpaste)
Mode of Action: React with Cellular Macromolecules
Example: Topical
