6-4: Control of Microbial Growth (and death) Flashcards
What is decontamination/disinfection
Neutralizing or removing microbes. Goal is to reduce numbers of potentially harmful organisms
What is sterilization
Process of killing all microbes. Either sterile (no microbes) or not
What is decimal reduction time
Amount of time it takes to reduce number of microbes by a factor of 10
What is thermal death time
Amount of time it takes to kill all cells at a given temperature
Decimal reduction time/thermal death time both depend on…
pH, [salt], moisture, presence of fats/sugars/proteins
What are autoclaves
Used to sterilized objects in healthcare, research using steam
What temperature is required to kill endospores using autoclaves
121C for 15 minutes
What is pasteurization
Heated for specific amount of time to eliminate pathogens and reduce spoiling agents
What causes milk to spoil
Heat-resistant lactic acid bacteria that survive pasteurization
What temp is milk pasteurized at
71C for 15 seconds
What is ultraviolet light and ionizing radiation used for
UV = damages DNA and lethal to microbes at high intensities, sterilize surfaces but low penetration
Ionizing R = gamma rays, improved penetration , used to sterilize surgical supplies, labware
What is filtration
Passing liquids through filters with pore size of ~0.2 microns to sterilized
Not as reliable as autoclaving, but does not cause damage like heat
How do soaps/cleaners disrupt microbes
Membrane disruption, protein denaturation, oxidizing agents
What are sterilants
Kill all microbes e.g. formaldehyde
What are disinfectants
For surfaces, kill many/most but not all e.g. lysol
What are sanitizers
Less harsh to humans, generally less effective e.g. soaps
What are antiseptics
Kill or inhibit growth of microbes, non-toxic enough to use on tissues/wounds e.g. ethanol
What is an antimicrobial agent
Chemical that kills or inhibits microbial growth
Bactericidal vs bacteriostatic vs bacteriolytic
Cidal = kill cells
Static = inhibit growth, microbe not dead and can recover
Lytic = kills cells and cause them to lyse (no longer observable)
What is the MIC of a compound
Minimal inhibitory concentration = lowest conc. of a compound that fully inhibits growth
How can we assess antimicrobial activity
Solid media with antimicrobial disk placed on it, zones of inhibition
What are antibiotics
Medicines/molecules with antimicrobial properties used to treat infections
Specific mechanisms to target specific aspect of microbial biology that is absent/different in humans
What are topical antibiotics
Manufactured into creams/ointments
Who discovered the first true antibiotic? How?
Alexander Fleming (penicillin). Mold was secreting compound that kills bacteria
What was the first true antibiotic used in clinic
Prontosil
How do antibiotics work
Target essential processes such as CW biosynthesis, translation, DNA replication, essential biosynthetic processes
How does penicillin work
Inhibits penicillin binding protein activity, which catalyze transpeptidation reaction that crosslinks CW
Cell wall loses integrity, cells lyse
What soil-dwelling bacteria produce a large number of antibiotics
Streptomyces
How is antibiotic resistance a problem
Drugs that were once effective against pathogens unusable due to high resistance
Running out of options to treat MDR pathogen strains
Four mechanisms of antibiotic resistance
- Modification of drug target (enzyme mutation)
- Enzymatic inactivation of the drug (degrade)
- Preventing access to bacterial cell (efflux pump)
- Metabolic bypass (find another way to do what the drug is blocking)
How is persistence different than resistance
Persistence is when antibiotic-sensitive populations of bacteria include rare cells than are tolerant to antibiotics
Genetically unchanged, can be killed after emergence from tolerant state
Common route of persistence
Dormancy (slowing/shutting off metabolism)
Antibiotics depend on metabolism/growth to be effective
