Control microorganisms Flashcards
Name all control microorganisms
- Sterilization: killing all organisms
- Decontamination: Making safe for use
- Inhibition: limiting the growth of microorganisms
- ## Disinfection: killing pathogenic microorganisms
What are physical methods to kill microorganisms?
- Heat
- Radiation
- Filtration
What are chemical methods used on external surfaces?
Sterilants,disinfectants,sanitizers, antiseptics.
What are chemical methods used internally?
antibiotics, antivirals, antifungals
What is the decimal reduction time?
Time to reduce population of one tenfold
If temperature increase, decimal reduction time…
decrease!
The time necessary to kill a defined fraction is _________ of the initial cell concentration (90%). But the thermal death time is ________ of the initial cell concentration.
indenpendant
dependant
True or false
Different microorganisms have the same decimal reduction time if same temp. is used.
False, Different microorganisms have different decimal reduction time.
What is the thermal death time?
Time needed to kill all cells at a given temperature
True or false
Endospores need more time than vegetative cells to be killed by heat
True
What is autoclave?
a sealed device that uses steam under pressure, killing endospores in a decent amount of time (10-15 min). Water goes above 100 degres
What are the 2 different type of pasteurization?
Flash pasteurization: 72°C for 15s.
Bulk pasteurization: 65°C, 30min.–> cheaper, diff. taste
What is pasteurization?
is the process of using precisely controlled heat to reduce the microbial load in heat-sensitive liquids.
True or False:
Pasteurization kills all microorganisms.
False. It kills a lot of pathogenic microorganisms, but doesn’t kill everything.
Reduces the microbial load, increases the shelf life of the product.
What is the effect of radiation on microorganisms?
It reduces microbial growth.
What is the effect of UV light on microorganisms?
UV has sufficient energy to cause modifications and breaks in DNA, which inhibit replication, transcription and cause death.
What is ionizing radiation?
- Electromagnetic radiation that produces ions and other reactive molecules.
- Generates ions and hydroxyl radicals
- Sources of radiation include cathode ray tubes (electrons), X-rays, and radioactive nuclides
- Radiation is used for sterilization in the medical field and food industry
What is one positive aspect of filter sterilization?
Filtration avoids the use of heat on sensitive liquids and gases
Name 2 types of filters.
Depth filters and membrane filters
What is the difference between depth and membrane filters?
DEPTH FILTERS: Fibrous sheet or mat made from an
array of fiber (paper or glass). Used to sterilize liquid, air. HEPA filters
MEMBRANE FILTERS: Function more like a sieve
A type of membrane filter is the nucleation track (nucleopore) filter.
Filtration speed can be increase by syringe, pump, or vacuum
Antimicrobial agents can be classified as: (3 things..)
- Bacteriostatic
- Bacteriocidal
- Bacteriolytic
What is the definition of Bacteriostatic?
Inhibits growth of microorganisms
What is the definition of Bacteriocidal?
Kill all cells
What is the definition of Bacteriolytic?
Kill cells by inducing lysis
Name 4 ways to measure antimicrobial activity
- Minimum inhibitory concentration
- Minimum lethal concentration
- Minimum bacteriocidal concentration
- DEcimal reduction time
- Disc diffusion assay
What is the definition of minimum inhibitory concentration?
smallest amount of an agent to inhibit growth of microorganism.
What is the definition of minimum lethal concentration
smallest amount of an agent that kills test ORGANSIMS
What is the definition of minimum bacteriocidal concentration?
smallest amount of an agent that kills test BACTERIA
What is a disc diffusion assay?
- Antimicrobial agent is added on a paper disc…
- MIC is reached at some distance of the disc
- Zone of inhibition= area where there is no growth
What are antimicrobial agents used for?
Used to prevent spreading of a pathogen in a certain envrionment. Prevent contamination of a host, cure superficial bacterial infection.
Describe the 2 categories of antimicrobial agents for external use.
- Antimicrobial agents used in commercial and industrial application (ex: chemicals in paper, air conditionning…
- Products used to prevent growth of human pathogens in inanimate environments and on external body surfaces. –> sterilants, sanitizers, desinfectants and antiseptics
What antimicrobial agent kills all microorganisms incluing endospores?
Sterilants. Also called cold sterilization
What do disinfectants and sanitizers do?
applied to nonliving objects or surface (can be toxic for animals/humans). Do not kill endospores.
What do antiseptics do?
applied to the surface of living :ssues or skin (must not be toxic for animals/humans). Do not kill endospores.
What are antimicrobial drugs?
Antibiotics, antifungals, antivirals: applied outside or inside the body of animals/humans (must not be toxic for animals/humans). Do not kill endospores.
What is an exemple of an agent that is a disinfectant, antiseptic and sterilant?
Halogens (but they are not all at the same time….)
Sodium Hypochlorite
What is a positive aspect of antimicrobial drugs?
Can be used on humans and animals because they have minimal side effect on the host—> because they have a specific target —> target a specific thing in the bacteria
What are the characteristics of a good antimicrobial drug?
- NO severe side effects, must be far more toxic for bacteria than mammalian cells.
– Low risk/benefit ra:o.
– Broad spectrum of ac:vity to facilitate rapid medical intervention.
– Appropriate bioavailability and pharmacokinetics (must reach the site of infection).
– Low cost to develop and manufacture.
What is selective toxicity?
is is the ability to kill a phatogen without affecting the host
Who specifically studied selective toxicity in the early 1900s?
Paul Ehrlich
Name 4 synthetic antimicrobial drugs.
- Ionazid
- Nucleic acid base analogs
- Quinolones
- Sulfa drugs
What is ionazid and give and exemple.
Ionazid is a synthetic antimicrobial drug. interfers with synthesis of mycolic acid. Works only against MYCOBACTERIUM.
What is a growth factor analog and give exemples.
Growth factor analog are structurally similar to growth factors but do not function in the similar way the cell. Sulfa drugs and Ionazids are growth factor analogs.
What are sulfa drugs. Give an exemple.
Sulfa drugs are growth factor analogs. They are bacteriostatic. SULFANILAMIDE is an exemple.
What are nucleic acid base analogs, what do they do, give an exemple.
They are formed by bromine and fluorine. They stop DNA replication and translation.
What are Quinolones?
Antibacterial compounds that interfere with DNA GYRASES (control DNA supercoiling).
What are antibiotics?
ANTIMICROBIAL AGENT that are NATURALLY PRODUCED by a variety of bacteria or fungi to kill or inhibit other microorganisms.
true or false
Antibiotics can be modified in a laboratory.
true. They are called semisynthetic antibiotics.
Why do Gram + and Gram - bacteria rect differently to antibiotics?
Because of cell wall.. major factor…
What is the most important antibiotic group of all times?what antibiotics does it include?
b-lactams. Includes PENICILLINS, CEPHALOSPORINS, and CEPHAMYCINS.
Describe penicillins.
- Discovered by FLEMING
- Primarily efficient agains GRAM +
- Some synthetic forms are also effective agains gram-
- INHIBITS CELL WALL SYNTHESIS
Describe cephalosporins.
- b-lactam antibiotic
- produced by a fungus (Cephalosporium)
- Same mode of action as the penicillin
- Commonly used to treat ghonorrea
Describe the mode of action of B-Lactams
penicillin binds to transpeptidase. B-lactams are BACTERIOCIDAL or BACTERIOLYTIC (depending..) . Can also be bacteriostatic.
Name Antibiotics made by prokaryotes.
Aminoglycosides
Chloramphenicol
Macrolides
tetracyclines
