EX2 Effects of Antibiotics on Bacteria - Bailey Flashcards
In 1920, Alexander Flemming described the potential usefulness of what
penicillin
In 1940, Ernst Chain and Howard Flory demonstrated the water and effectiveness of penicillins in what
humans (in WWII)
What are the two mode of action of antibiotics
bactericidal; kill bacteria
bacteriostatic; reduce metabolic activity
An ideal antibiotic has what four things
broad spectrum of activity
would not induce resistance
high therapeutic index
selective toxicity
This is the ratio between a toxic dose and effective dose; if the ratio is 1, then you need a toxic dose to eradicate the microbe
high therapeutic index
What four things are unique to microbes that help achieve selective toxicity
cell wall
enzymes for replication, transcription, and translation
essential metabolites
ribosomes
What are the 5 ways that antibiotics inhibit bacteria
cell wall synthesis membrane function protein synthesis (ribosomes) antimetabolites inhibition of nucleic acids
What are some places of antibiotic inhibition involving cell wall synthesis
NAG binding with NAM NAG/NAM elongtation formation of NAM side chains transport of chain to periplasmic space peptide chain cross linking
How does penicillin disrupt cell wall synthesis
prevents the formation of peptide bonds between side chains
What structure does penicillin use to disrupt cell wall synthesis
D-alanine; penicillin is cleaved instead of the D-alanine causing substrate overload, and cleaved penicillin is more toxic
What is used to disrupt cell membrane function
polymyxin B sulfate by binding to LPS layer, disrupting it
What is targeted in inhibiting protein synthesis
ribosome
What are some of the places of antibiotic inhibition involving ribosomes
prevention of 50S and 30S binding
prevention of tRNAs to bring AAs to 30S
change configuration of ribosome to change the tunnel
prevent 30S and 50S from binding to mRNA start site
prevent elongation of AA chain
What can be an issue with inhibitors of DNA replication
they bind to DNA are are too toxic too use
What is the one antibiotic that binds to DNA, being covered to an active from by anaerobic microbes
metronidazole
Antibiotics like nalidxic acid and quinolines affect what
DNA gyrase
Antibiotics like rifamycin inhibit this
RNA polymerase
Hows does sulfanilamide act as a antimetabolite
PABA (para-aminobenzoic acid) forms folic acid in bacteria, and the sulfanilamide disrupts the formation
Penicilin, clindamycin, and cephalosporins are typically used to treat what
odontogenic infections (clindamycin also treats abscesses)
metronidazole and tetracyclines are typically used to treat what
peridontitis (metronidazole also treats abscesses)
What are the three steps in the action of antibiotics
drug penetrates the envelope
transport into cell
drug binds to target
What are the three mechanisms of drug resistance
synthesis of enzymes that inactivate the drug
prevent of access to the target site
modification of the target site
What are the two ways in which a bacteria can prevent an antibiotic form accessing the target site
inhibiting uptake
increasing secretion of the drug
Some bacteria can produce enzymes which do what to penicillin
break the β-lactam ring; inactivating the bond
How to antibiotics enter the cell
through porins
Bacteria change the structure of porins, which increase the resistance to which antibiotics
tetracyclines and quinolones
Some bacteria develop this to remove antibiotics from themselves (all classes of bacteria have this
efflux pumps; pump the drug out
How does a microbe modify the target site
modify enzyme activity
alteration of metabolic pathway (high affinity, etc.)
How does antibiotic resistance spread
chromosome associated resistance (mutations)
plasmid mediated resistance
rapid spread resistance
What is the main reason it is important to finish the course of an antiobiotic
high resistant bacteria take a longer time to die, if you stop taking the antibiotic prematurely, then the number of antibiotic resistant bacteria increases
What three things are used to combat an antibiotic resistant pathogen
synergism (2+ antibiotics)
antagonism
indifference
What are the drawbacks to administering an antibiotic cocktail
failure to eliminate pathogen; superinfection synergistic toxicity (multiplied)
True or False
Antibiotics are effective against all microbes
False; not viruses, fungi, etc.
