Antibacterials Flashcards
What is the morphology of streptococci?
Gram positive cocci in chains
What is the morphology of staphylococci?
Gram positive cocci in grape-like clusters
True or false: all bacteria have a cell wall consisting of peptidoglycan
True
What is peptidoglycan?
a macromolecule composed of peptides and sugars
What does LPS consist of?
Phospholipid and polysaccharides
What is the major difference between eukaryotic cell membranes and prokaryotic?
Prokaryotes have sterols
What bacteria are catalase positive?
Staph
Catalase positive, coagulase positive = ?
Staph aureus
What is the most common agent for UTIs?
E.coli
Clostridium is gram positive or negative?
Positive
What agar is needed to grow Neisseria gonorrhoeae?
Chocolate agar
What is the effect of LPS on antibiotics?
Retards or prevents penetration of bulky, high molecular weight abx
What is the effect of the lipid bilayer of the cytoplasmic membrane on abx?
Penetration of water soluble drugs is severely hindered
What is the effect of hydrophilic pores on abx?
Allows penetration of water soluble molecules
What is the effect of nutrient receptors proteins on the outer membrane of bacteria on abx?
Sideomycins utilize these natural receptors
Macrolides work well against what type of bacteria?
Gram positive, generally
What is the function of teichoic acid on abx?
Strong anionic character of these will affect the rate of penetration
What is the effect of the gram positive lipid bilayer?
Affect the rate of penetration of lipophilic drugs
What is the effect of nutrient transport proteins on Gram positive bacteria and abx?
Facilitate rapid penetration of agents similar in structures
What is the EC50 for abx?
Inhibitory concentration at which 50% of the organisms are killed or stop growing
What is the Emax for abx?
Maximum microorganism death or impaired growth
What are the three major ways to inhibit bacteria?
- Disrupt coding/genetic machinery
- Block protein synthesis
- Disrupt exterior of the cell
True or false: bactericidal and bacteriostatic effect can sometimes be dose-dependent
True
Is tetracycline a broad or narrow spectrum abx?
Broad
What is pre-emptive therapy?
Treatment of high-risk patients that have become infected, but are asymptomatic
What is prophylactic therapy?
treatment without infection
What is empirical therapy?
Treatment of a symptomatic patient without further testing or confirmation of the organism
What is definitive therapy?
Treatment once the pathological organism has been identified and appropriate drug identified
What is suppressive therapy?
Generally a low dose therapy used as a secondary prophylaxis.
What is the difference between transduction and transformation?
What are the 6 drug resistant organisms?
Enterococcus faecium Staph aureus Klebsiella pneumoniae Acinetobacter baumannii Pseudomonas aeruginosa Enterobacter species
(ESKAPE)
What is the therapeutic use of daptomycin?
Complicated skin infection, endocarditis
What is the MOA of resistance to daptomycin?
Specific gene mutation (mprF) that results in a change in membrane charge (add lysine). There is an overall increase in the net positive charge which will repel the abx with cationic properties
What is the therapeutic use of tetracycline?
Broad specturm abx
What is the MOA of resistance to tetracycline?
Expression of an efflux pump
What is the therapeutic use of metronidazole?
Abdominal infections, clostridium difficile
What is the abx of choice for C.diff?
Metronidazole or vanco if bad
What is the MOA of resistance to metronidazole?
Metronidazole needs to be reduced to generate ROS. Mutations in rdxA gene (oxygen-sensitive nitroreductase) alters or decreases activation of the drug
How is metronidazole a prodrug?
Needs to be reduced to generate ROS
What is the MOA of resistance to aminoglycosides?
Aminoglycoside-modifying enzymes chemically modifies the abx and alters binding of the drug to its target
What type of abx is amoxicillin?
Beta-lactam broad spectrum
What is the MOA of resistance with amoxicillin?
Expression of the enzyme beta lactamase which can hydrolyze the lactam ring of amoxicillin and render the compound ineffective
What is the therapeutic use of trimethoprim and sulfonamides?
UTIs
What is the MOA of resistance to trimethoprim and sulfonamides?
Expression of the drug insensitive enzymes dihydropteroate synthase and dihydrofolate reductase
What is the drug that can inhibit beta lactamase?
Augmentin (clavulanic acid)
What is the therapeutic use of vanco?
Bloodstream infections
What is the MOA of resistance to vanco?
Substitution of the peptidoglycan stem so that agent can no longer bind to the target
What is the MOA of trimethoprim and sulfonamides?
Sulfa inhibits dihydrofolate synthase
What is the MOA of trimethoprim?
Inhibits dihydrofolate reductase
What is the MOA of vanco?
Binds to d-ala in the growing peptidoglycan chain, causing steric hindrance
