Unit 4 Exam Guide Flashcards
What are the methods of chemical control that we discussed? Be able to identify whether a given method is effective at killing all, most, or some microbes.
Sterilization: Destroys EVERYTHING, including spores
Disinfection: Kills most cells, probably not spores (requires some time)
Microbicidal Agents: Agents that kill bacteria
Microbistasis: Puts them in the “pause” mode (e.g. put them in freezer)
Antiseptics: Used on living organisms to prevent infection
Sanitization: Keeping things clean
What is the difference between microbicidal and microbistasis? Provide examples of each.
Microbicidal: Kills bacteria
Microbistasis: Puts them in “pause” mode
Identify the types of microbes that would fall in the categories of high, moderate, and least resistant to antimicrobial agents.
High
-Bacterial endospores (e.g. Clostridium, Bacillus)
-Prions
Moderate
-Protozoan cysts
-Fungal sexual sores (zygospores)
-Mycobacterium vegetative cells
-Gram-neg bacteria
Least
-Most bacterial vegetative cells
-Fungal spores
-Enveloped viruses
-Yeast
What is the definition for microbial death?
How is this different from how we define death in larger, eukaryotic organisms, such as animals? Why is the definition for microbes different than for humans?
Microbial death: permanent loss of reproductive capability under optimal environmental conditions
Larger, eukaryotic organisms: Irreversible cessation of all vital functions (brain activity, heartbeat, respiration)
Microbial viability: Assessed in context of infection control, fermentation
What is the relationship between the number of viable microbial cells and time after administration of an antimicrobial agent? Will it be the same for all agents?
It is an inverse relationship. As time increases, the number of viable microbial cells decreases. It is not the same for all agents
How would the concentration of the antimicrobial agent affect this relationship?
The greater the concentration, the lower the number of viable microbial cells
Define antibiotic. Where in nature do we find these? How antibiotics different from synthetic drugs?
In nature: from spore-forming bacteria and fungi; used in natural settings for competitive advantages and host defense
Define competitive inhibition. What groups of drugs are effective because of their role as competitive inhibitors?
A synthetic drug will adhere to the enzyme’s active site, taking the place of the substrate.
Sulfa drugs
What criteria should drugs used in microbial chemotherapy meet?
Kill the infection, but leave the host cells alone
What are the five modes of action of chemotherapeutic drugs? How does each effectively kill/inhibit microbes? Be able to provide examples of drugs that use these different modes.
Cell wall: Very effective, esp. against Gram +
Cell membrane: Effective, can allow foreign entities into cell
Protein & DNA/RNA synthesis: Effective
Alter protein function: Causes misfolding
Block key metabolic pathways:
What is the best preventative measure against viruses?
Differentiate between broad and narrow spectrum antibiotics. Which is most likely to cause a superinfection? Why?
Broad: Targets a variety of bacteria; both gram positive and gram negative
Narrow: Target specific types of bacteria; usually gram positive OR gram negative, not both
Broad spectrum is more likely to cause a super infection because it may end up killing bacteria of the normal/healthy microbiome. Then, opportunistic pathogens will be able to proliferate.
What are the different modes of action of antiviral drugs?
Barring penetration
Blocking replication or protein synthesis
Prevent maturation
What is the difference between autoclaving and lyophilization? What is the purpose of these methods?
Autoclaving – High pressure and temperature to kill microorganisms; sterilization
Lyophilization - (aka freeze-drying), removes water from frozen product; preservation, maintains viability of life forms
Why is it so hard to kill microbial species that form endospores?
What are the two genera of bacteria that we know form endospores?
Streptomyces, Bacillus
If you want to make sure that endospores are killed, what method would you use?
What physical control mechanisms did we discuss in class?
Heat
-High temperature = microbicidal
Low temperature = microbistatic
-Moist heat is cooler AND quicker, than dry heat
-Thermal death time: Shortest time it takes to skill a microbe at a specified temperature
-Thermal death point: Lowest temperature needed to kill all microbes in a sample/10 minutes
Autoclave: Steam under pressure
Tyndallization: Steam
Filtration
Charcoal, diatomaceous earth
How is radiation used?
Radiation: Energy emitted from atomic activities and dispersed at high velocity through matter or space
Three ways:
Gamma Rays
X Rays
Ultraviolet
What type of radiation is the best means for microbial control?
Gamma Rays
What is the difference between ionizing and non-ionizing radiation and how is each effective at controlling microbial populations?
Ionizing: Causes breaks in DNA strands
Nonionizing: Causes bases of the same strands to bond together
What is chlorhexidine and why is it so popular as an antimicrobial in hospitals?
Benefits:
Bactericidal (Both gram + and -)
Disrupts cell membranes
Denatures proteins
Low Toxicity
Fast-Acting
Control MRSA outbreaks in hospitals
What patient factors must be considered (by a faciliy) when choosing a drug? Why?
Effective at low concentrations
Fast
Broad-spectrum
Stable in water/alcohol
Non-toxic to humans
What is used to combat infection by fungi and parasitic worms?
Fungi: Diflucan, monostat
Antihelminth drug therapy
