Microbiology Chapter 10
Terms in this set (40)
Why is it difficult to find good chemotherapeutic agents against viruses?
Viruses depend on the host cell's machinery, so it is hard to find a viral target that would leave the host cell unaffected.
What is meant by selective toxicity?
Chemotherapeutic agents should act against the pathogen and not the host.
Why are chemotherapeutic agents that work on the peptidoglycan cell wall of bacteria a good choice of drug?
Humans and other animal hosts lack peptidoglycan cell walls
Why is polymyxin only used on the skin
It can also damage living human cell membranes, but the drug is safely used on the skin, where the outer layers of cells are dead.
Quinolones and fluoroquinolones act against what bacterial target?
What is meant when a bacterium is said to become "resistant" to an antibiotic?
The bacterium is neither killed nor inhibited by the antibiotic.
When a patient is treated with antibiotics, __________.
the drug will kill or inhibit the growth of all of the sensitive bacterial cells
The process of acquiring antibiotic resistance by means of bacteriophage activity is called
Which of the following mutations would not result in antibiotic resistance?
R-plasmids are most likely acquired via
β-lactamase production is an example of which of the following types of resistance?
inactivation of the drug
Prokaryotes contain _____ ribosomes.
Antimicrobial drugs are selectively toxic. This means _____.
the drugs are more toxic to the pathogens than to the patient
The tRNA molecule holding a growing polypeptide chain is at the
P sites hold developing polypeptide chains
Which category of antimicrobial drug works by changing the shape of a ribosome?
Which category of antimicrobial drug essentially acts to stall a ribosome as it reads mRNA
Chloramphenicol blocks the action of the large (50S) subunit. This essentially _____.
prevents the formation of peptide bonds
Which antimicrobial drugs affect the structure of the ribosome itself?
aminoglycosides, antisense nucleic acids, and oxazolidinones
Which category of drug is complementary to mRNA of the pathogen?
antisense nucleic acids
Any drug that acts against a disease is called a ________ agent
effective against few organisms
effective against many organisms
•May allow for secondary or superinfections to develop
Inhibition of cell
Inhibition of general
Inhibition of DNA
or RNA synthesis
Inhibition of pathogen's
attachment to, or
recognition of, host
Mechanisms of Action: Inhibition of cell wall synthesis
*Most in this group are considered narrow spectrum
•Prevent bacteria from increasing amount of peptidoglycan
•Can only act on actively growing bacteria
•Beta-lactams are most prominent in this group
Mechanisms of Action: Inhibition of protein synthesis
•Some antibiotics target prokaryotic ribosomes
•Prokaryotic ribosomes are 70S and eukaryotic are 80S
•These drugs candamage ribosomes of mitochondria
*Most antibiotics that target protein synthesis are broad spectrum
Mechanisms of Action: Disruption of the cytoplasmic membrane
•Drugs form a channel through the membrane, damaging integrity
•Polyenesattach to ergosterol, a lipid in fungi membranes
•Amphotericin Bis considered a broad spectrum antifungal
Mechanisms of Action: Inhibition of metabolic pathways
•Unique metabolic reactions in microorganisms are good targets for antimicrobial drugs
•Sulfanilamideblocks the production of nucleotides in bacteria
Inhibition of nucleic acid synthesis
•Drugs that block DNA replication or RNA transcription can affect bothprokaryotes and eukaryotes
•These drugs are considered broad spectrum
Mechanisms of Action: Inhibition of attachment(used for viruses)
•Antiviral agents can target the ability of virus to attach to host cell
smallest amount of drug that will inhibit growth and reproduction
Kirby Bauer test
*Looks at growth inhibition
*Diffusion susceptibility test
minimum amount of drug required to kill the microbe
Seven known mechanisms of resistance
•Production of enzyme that destroys or deactivates drug
•Slow or prevent entry of drug into the cell
•Alter target of drug so it binds less effectively
•Alter their own metabolic chemistry
•Pump antimicrobial drug out of the cell before it can act
•Bacteria in biofilms can resist antimicrobials
Horizontal gene transfer:
R plasmids (Resistant plasmids) can hop to bacteria via conjugation, transduction, or transformation