Week 10: Using Growth Patterns for Diagnosis and Treatment (Part 2) Flashcards
where is the highest concentration of antibiotic on a kirby bauer assay?
closest to the disc
what is the name of what develops around the antibiotic discs on a kirby bauer?
zone of inhibition
what influences the size of the zone of inhibition? (2)
susceptibility of organism tested, as well as other factors
how does kirby bauer work?
deposit disc, watch the zone of inhibition grow
what is kirby bauer testing for?
susceptibility of a bacteria to an antibiotic
why is it important to know what a bacterium is susceptible to?
name three antibiotics that we used in the lab
- kanamycin/tetracycline
- penicillin
- novobiocin
what does kanamycin/tetracycline target? what does that cause?
targets the 30S ribosomal subunit, causing misreading of t-RNA
name the broad spectrum antibiotics
kanamycin/tetracycline
name the narrow spectrum antibiotics
penicillin, novobiocin
broad or narrow spectrum: kanamycin
broad
broad or narrow spectrum: tetracycline
broad
broad or narrow spectrum: penicillin
narrow
broad or narrow spectrum: novobiocin
narrow
what does penicillin target?
transpeptidase
what is transpeptidase? why are we talking about it rn?
the enzyme that forms the crosslinking in the peptidoglycan layer of the membrane. targeted by penicillin.
what does novobiocin target?
DNA gyrase of Staphylococcus species
what process does penicillin target?
peptidoglycan synthesis of bacteria
DNA gyrase of Staph. species is targeted by?
novobiocin
30S ribosomal subunit is targeted by…
kanamycin or tetracycline
transpeptidase is targeted by
penicillin
what is penicillin effective against, ineffective against? why?
G+: effective
G-: ineffective
has to do with the thickness of the cell wall
pros of broad spectrum drugs
effective against a wide variety of bacteria, useful when the exact pathogen is not known
cons of broad spectrum drugs
the use of broad spectrum antibiotics play a key role in the spread of antibiotic resistance
pros of narrow spectrum drugs
effective only against a subset of bacteria, depending on its mode of action. helps stop the spread of antibiotic resistance
cons of narrow spectrum drugs
need to know more about the identity of the bacteria first, effective only against a subset of bacteria
what is an example of how antibiotic resistance is on the rise?
MRSA
what does MRSA stand for?
methicillin resistant Staphylococcus aureus
what is MRSA?
a common pathogen of skin and wounds that spreads through contact with infected/carrier individuals
how to treat MRSA infection?
drugs with a low therapeutic index
how to prevent spread of MRSA infection?
proper hygienic practices
why is drug resistance growing?
misuse/irresponsible use of antibiotics
