Antibiotics 3 and 4 Flashcards
polymyxin B
selective against G- enteric rods
binds LPS and then cytoplasmic phospholipids in membrane, causing membrane leakage
used as a topical agent
good against PA
daptomycin
lipopeptide that inserts into membrane of bacteria
cubicin
IV
only works on G+
aminoglycosides
bacteriocidal, ex. streptomycin, gentamycin
proposed mechanisms
binds to 30S distorting acceptor site and causing misreading that leads to bad proteins
at higher concentrations, it inhibits formation of the initiation complex
some bacteria are resistant. is inhibited under anaerobic or acidic conditions
streptomycin
only used for TB and select other
once used for G-
requires aerobic conditions
gentamycin
bacteriacidal
disrupts 30S ribosme, but also other things, so resistance cannot form in one step
requires aerobic conditions
under what conditions are aminoglycosides inhibited
anerobic, acidic conditions
tetracyclins
ex. tetracyline, doxycycline, minocycline
bacterioSTATIC
taken orally. broad spectrum. cant be taken pregnant or under 8.
inhibit 30 S ribosome
what are the important tetracyclins?
tetracycline, doxycycline, minocycline
inhibitors of 50S ribosome
erythromycin (macrolide) choramphenicol clindomycin azithromycin sreptogramins
erythromycin
bacterioSTATIC. blocks chain elongation. binds 50S
similar spectrum to penicillin G
azithromycin
related to erythromycin, but higher activity and broader spectrum. sustained tissue concentrations
bacterioSTATIC. binds 50S
chloramphenicol
bacterioSTATIC. blocks chain elongation. binds 50S
can cause lethal aplastic anemia.
useful against bowel anaerobes
clindamycin
STATIC. derivative of lincomycin. binds 50 S subunit
activity against G+ and anaerobes
binds 50S subunit. inhibits peptidyl transfer
sreptogramins
STATIC. binds 50 S.
potential for treating resistant bacteria- MRSA VREF, etc.
2 types: dalfopristin and quinupristin
what are the 2 types of sretpogramins
dalfopristin and quinupristen
combined form synergin
oxazolidinones
STATIC. active G+
linezolid (zyvox)
IV and oral
potential for treating resitant MRSA, VREF, VRSA
inhibits tRNA translocation
mupirocin
STATIC at low concentrations, CIDAL at high concentrations
inhibits tRNA
useful for treatment of MRSA
quinolones
ciprofloxacin, moxiflaxacin
inhibits DNA gyrase necessary for DNA synthesis
CIDAL
rapidly emerging resistance- no longer MRSA drug
no pregos
examples of quinolones
ciprofloxacin, moxiflaxacin
nitroimidazoles
ex. metronidazole
binds DNA and fragments it
anaerobic, CIDAL
requires anerobic conditions
rifampin
broad spectrum, CIDAL
binds RNA polymerase, inhibiting binding to DNA
useful w/ isoniazid agaisnt TB
efficiently secreted in saliva
ethambutol
anti TB, unknown MOA, STATIC
pyrazinamide
anti TB, unknown MOA, CIDAL
require mycobacteria amidase
what are the indications for using multiple drugs?
synergy can be expected pathogens require likelihood of resistance is reduced dosage of a toxic drug can be reduced poly-infection
what are the disadvantages of
side effects
antagonism
cost
resistance
general mechanisms of resistance
enzymatic inactivation
cannot enter cell or is pumped out
cell contains altered enzyme that resists drug
binding target replaced
enzymatic inactivation examples
b-lactamases
chlorampheticol acteyltransferase
erythromycin esterase
altered membrane permeability resistance examples
outer membrane porins decreased
inner membranes transporters altered
antibiotic flux from the cell resistance examples
tetracycline resistance
alteration of ribosomal target resistance examples
erythromycin. methylation of 23S rRNA
streptomycin- alter S12 of 30S
alteration of cell wall precursor examples
vancomycin resistance
enzyme forms D-ala-D-lactate instead of D-ala-D-ala
alteration of target enzymes examples
PBP- methicillin
DHF synthetase- sulfonamide
bypass pathways
trimethroprim resistance- other ways to form dna precursors
