Antibiotics Flashcards
what do you need for bacteria to grow
nutrients
appropriate physical and chemical environment
4 stages of bacterial growth graph
lag phase - active and growing and if nutrients plentiful go to log
log/exponential phase
stationary phase - build up waste produces promote cell death
death phase
what features do you look for in a good antibiotic
effective safe slow emergence of resistance long half life good tissue distribution oral bioavailability cheap
what ribosomes do bacteria have
70S
can antibiotics halt exponential growth giving chance for immune system to bring it down or be bacterialcidal and deplete them cause them to rupture
yes
name an aerobic bacteria
gram negative neisseria.spp
name an anaerobic bacteria
clostridium.spp gram postiive
what are staphcoccus, strept, listeria, klebseilla, e coli all examples of
facultative anaerobes - replicate in aerobic but cn switch if conditions dictate it
what are the 5 classifications of antibiotic mode of action
Inhibition of cell wall synthesis metabolic antagonism interference with nucleic acid synthesis inhibition of protein synthesis action on membrane
what type of cell wall does bacteria have
Peptidoglycan ( N-acetylglucosamine and N-acetylmuramic acid amino acid crosslinked)
examples of antibiotics that destroy the cell wall
penicillins e.g. amoxicillin
Penicillins work by bursting the cell wall of bacteria. Drugs in the penicillin class work by indirectly bursting bacterial cell walls. They do this by acting directly on peptidoglycans, which play an essential structural role in bacterial cells
how does metabolic antagonism work
Interrupting bacterial metabolic pathways that dont exist in humans
Interrupt bacterial metabolic pathways - folic acid
why is folic acid needed in bacteria
Folic acid is an essential nutrient necessary for protein and nucleic acid synthesis (DNA and RNA). Folic acid is synthesized by bacteria from the substrate, para-amino-benzoic acid (PABA), and all cells require folic acid for growth.
examples of antibiotics that inhibit metabolic pathways
Eg trimethoprim ( competitive ) and sulfadiazine ( abtruct it thus preventing Dna synthesis so inhibit further replication)
which enzymes unwinds DNA
DNA gyrase
Quinoloes such as ciprofloxacin inhibit what enzyme
DNA gyrase
rifamycins such as rifampicin inhibit what enzyme
RNA polymerase
what is a pro drug
Drugs can be metabolized by several tissues and organs, such as the kidneys, lungs and intestines, but the main site of metabolism is the liver, which is rich in enzymes. A prodrug is a medication that the body converts into a pharmacologically active drug after it is administered.
during inhibition of protein synthesis you can use macrocodes , aminoglycosides and tetracyclines
what do ahminoglycosides do
potent bactericidal antibiotics that act by inhibiting bacterial protein synthesis , thereby binding bacterial 30S and 50S ribosomal subunit, inhibiting the translocation of peptidyl-tRNA from the A site to the P site and also causing misreading of mRNA
e.g. gentamicin
what are macrocodes e.g. clarithromycin
treat respiratory and skin and sexually transmitted infections
bind to 50S subunit of the ribosome and inhibit protein synthesis
fucntion of tetracycline such as doxycycline
repsriaotry tract infections
Reversibly binds to receptors on the 30S ribosomes subunit of the bacteria preventing attachment of tRNA to RNA complex
in the 5th mechanism of bacteria destruction antibiotics can attack the cell membrane - Colistimethate sodium can be used but for what bacteria is this normally reserved for
reserved for gram-negative infections resistant to other antibacterials
what is the pneumonic to remember bactericidal (kills bacteria) antibiotics
BANG Q RIP beta-lactams aminoglycosides nitroimidazoles glycopeptides quinolones rifampicin polymyxins
what is the pneumonic for bacteriostatic( stops bacteria from reproducing) antibiotics
Ms.COLT marcolides sulfonamides chloramphenicol oxazolidinones lincosamides tetracyclines
is gentamicin absorbed from the go tract
no
mutated/acquired bacteria produce beta-lactamase - what does this do
enzyme that provides multi-resistance to Beta lactame antibiotics such as penicillin
what are the 4 mechanisms of acquired antibiotic resistance
- Spontaneous mutation- when multiplying in DNA changing susceptibility of bacteria to drug
- Conjugation- bacterial sex uses plasmids taking DNA from bacteria to another
- Transduction - phage mediated - virus that infects bacteria- taking DNA
- Transformation - bacterial able to incorporate making DNA into its genome
These are all hrizontl transformations from one bacteria to another
4 main modes of resistance
Altered uptake - reduce mutations entry to bacteria by removing transporter,
promote removal of drug
Drug inactivation- -beta lactamase
Altered target site - altering subunit within ribosomes
Altered metabolic pathway
