Ch.9: Controlling Microbial Growth In The Environment Flashcards
what is antiseptic?
antimicrobial chemical used to kill microbes on tissues
what is antisepsis?
reduction of the number of potential pathogens
what is disinfectant?
antimicrobial chemical used to kill microbes on surfaces
Describe microbial agents
-Do NOT simultaneosuly kill all cells
-some microbes require longer exposure to an agent before death
what is micorbial death?
-permanent loss of reproductive ability under ideal conditions
-constant
what are actions of antimicrobial agent alteration of cell wall?
-cell wall helps to maintain cellular integrity
-disrupt its structure, leading to cell rupture and death.
what are exceptions of alteration of cell wall?
viruses
-viruses tolerance depends on structure
what is a nonenveloped virsus
have greater tolerance to harsh chemicals
what is a enveloped virus
are enveloped by a portion of plasma membrane from host cells
what are ways to damage proteins and nucleic acids
-chemicals, radiation, and heat can damage nucleic acids
how to choose an antimicrobial agent?
-inexpensive
-fast-acting
-stable during storage
-controls microbial growth while being harmless to humans/animals/objects
site to be treated
not to be used on humans, animals, fragile objects
-harsh chemicals
-extreme heat
site of medical procedure
-Surgical (penetrates skin, major protection for inner tissues, steralized)
-Topical (skin or mucous membranes, disinfected)
what are the factors that affect efficiency of antimicrobial?
1.) Site to be treated
2.) Relative susceptibility of microbe to an antimicorbial method
3.) Environmental conditions
Low-level germicide
vegatative bacteria, fungi, protozoa, some viruses
intermediate-level germacides
kills fungal spores, protozoan cysts, viruses, pathogenic bacteria
High-level germicide
kills all pathogens and endospores
What are endospores
most resilient form of life
what are myobacterium
cell wall contains large amounts of waxy lipid survive drying, protection from water-based chemicals
what are protozoan cysts
protects from dessication, shield from radiation and heat, dormant
what are prions
cause degenerative brain disease, more resistance than any living thing
environmental conditions
temperature and pH
-affect death rate
-affect efficacy
-warm better than cool
what does acidic pH do
enhance effect of high temp.
what does organic material do
-these interfere with the penetration of antimicrobial agents
ex:-feces, vomit, blood, biofilms
What is a Biosaftey Level 1 (BSL-1)?
Handling pathogens that do not cause disease in healthy humans
ex: opportunistic pathogens
what is a Biosafety Level 2 (BSL-2)?
Handling moderately hazardous agents
ex:our lab
what is a Biosafety Level 3 (BSL-3)?
Handling microbes in safety conditions
ex:enhanced PPE
what is a Biosafety Level 4 (BSL-4)?
Handling microbes that cause severe or fatal disease
ex: we dont know how to treat it
what are physical methods of microbial control?
-extreme temperatures (hot or cold)
-desiccation
-filtration
-osmotic pressure
-radiation
what is thermal death point?
lowest temperature to kill all cells in 10 minutes in a broth culture
what is thermal death time?
time to sterilize a volume of liquid at a set temperature
what does moist heat do?
Disinfects, sanitizes, sterilizes, pasteurizes
* Denature proteins
* Destroy plasma membrane
* MORE effective than dry heat
what are the methods in use for moist heat?
- Boiling
- Autoclaving
- Pasteurization
- Ultrahigh-temperature sterilization
what does boiling do?
Kills vegetative cells (bacteria/fungi), protozoan trophozoites, most viruses * TIME IS CRITICAL
* Different elevations require different time limits
* CDC recommends a roiling boil for 1 minute
who can survive boiling
-endospores
-protozoan cysts
-some viruses
what is autocalving?
Pressure applied to boiling water prevents steam from escaping
* Boiling temperature increases as pressure increases
* Autoclave conditions: 121oC; 15psi, 15 minutes
what is pasteurization?
Heating to high temperature that kills most of the bacteria
* Used for milk, ice cream, yogurt, fruit juices
* NOT sterilization
* Heat-tolerant microbes survive
what are dry heat methods
Used for material that cannot be sterilized with moist heat
* Denatures proteins and oxidizes metabolic and structural chemicals
* Requires higher temperatures for longer time than moist heat
* Incineration is ultimate means of sterilization
Why is slow freezing better than quick freezing?
Slow freezing causes less cell damage and preserves quality.
Why do some organisms survive freezing?
Not all enzymes denature during freezing.
Why cook frozen food fully?
Some bacteria survive freezing and need to be killed by cooking.
what is dessication in physical methods
Ancient method of microbial control
* Drying out
* Inhibits growth due to the removal of water
what is Lyophilization in physical methods?
Freeze-drying
* Used for long-term preservation of microbes
* Prevents formation of ice crystals
