Lecture 4: Antibiotics Flashcards
what is anti-biotic resistance?
ability of organism to grow in presence of something that should inhibit growth
what are colicins / holins?
small proteins that poke holes in membrane of other cells to damage integrity
how do colicins enter a host cell?
bind to membrane proteins
what are the 3 mechanisms of action by colicins?
- intracellular nuclease on DNA, rRNA, tRNA
- formation of depolarizing de-energizing ion-conducting channels in cytoplasmic membrane that damage it
- stop cell wall synthesis (no peptidoglycan?)
nature has created antibiotic naturally overtime by
natural selection
what are some ways in which natural antibiotics are modified to be therapeutic?
- hydrophilic / soluble
- less toxic
- smaller
- more stable
what makes a good target of inhibition for an antibiotic?
- something unique
2. something essential
examples of good targets of inhibition
peptidoglycan, cell wall, protein translation, ribosomes, dna replication, lipids
methicilins
amoxicilin, ampicilin, carbenicilin; naturally quite toxic
examples of protein synthesis inhibitor antibiotics
chloramphenicol, erythromycin, kanamycin, tetracycline, streptomycin
examples of DNA inhibitor antibiotics
ciprofloacin and other fluroquinolones
DNA gyrase inhibitors prevent ____ which makes an easy target for
unwinding of DNA to be replicated; innate immune system
examples of small peptide antibiotics
bacitracin, vancomycin
small peptide antibiotics typically come in what form?
topical creams that bind to membranes of cells
bacitracin targets
gram + cells
glycopeptide (Bacitracin)
glucose group that can bind to CW and stop CW replication
how are methicilins modified for therapeutic use?
B-lactam antibodies are modified
what is the function of B-lactams?
block CW biosynthesis by inhibiting transpeptide linkage to peptidoglycan
what are B-lactamases?
enzymes secreted by bacteria to cleave B-lactam rings to make the drug ineffective
what is added to antibiotics to act as a B-lactamase inhibitor?
clavulinic acid
what is a biofilm?
capsules from slimy, sticky film thats impermeable to external agents
what is especially bad about a biofilm?
protects bacteria while allowing them to be exposed to sub-lethal conditions that make them stronger
survival of bacteria with a biofilm depends on
size, integrity, shape
after treatment with colistin, a slide of bacteria will appear__ at the surface and ___ on the inside under a confocal scope
surface green = alive
red = dead bacteria
why are the inner parts of a bacteria killed by an antiobiotic?
there are aqueous channels in biofilms that antibiotics go through and killing inner, but not surface
what are efflux pumps?
multi-component protein channels in the bacterial membrane that pump out toxins
TF : efflux pumps existed before antibiotics
true
why did efflux pumps exist before antibiotics?
heavy metals, chemicals
efflux pumps span from ___ to ___
inner to outer membrane
parts of efflex pumps are embedded in
inner, outer membranes and periplasm
what is an example of natural anti-biotic?
streptomyces bacteria
how do streptomyces make anti-biotics?
secrete molecules that inhibit growth of other bacteria
2 examples of streptomyces bacteria
spreptomycin and kanamycin
would flagella be a good target for anti-biotics?
not necessarily, because swimming isnt everything
what is a common site of biofilms?
catheters and other medical plastics
what is added to catheters to prevent biofilm formation?
antimicrobials
