antibiotics 2 Flashcards
linezolid
an oxazoladinone
inhibits protein synthesis by binding 50S and prevents formation of initiation complex(70s complex)
effective against e faecalis (including VRE vanc resistant), s epidermidis (+MRS), S aureus (+MRSA), s haemolyticus, and s pneumoniae (+pen. resistant)
tetracycline
inhibits protein synthesis by binding 30s –> prevents binding of aminoacyl tRNA (elongation)
crosses outer mem using porin channel and inner mem using active transport (mammal cells lack this)
effective for all rickettsiae (rocky mountain spotted fever)
oral; anything else impairs ingestion
penetrates CNS
tigecycline
a glycylcyline that inhibits protein synthesis by binding 30s and prevents A site aminoacyl tRNA elongation
good for tetracycline resistant strains
streptomycin
an aminoglycoside; inhibits protein synthesis by binding 30s (in the 16s rRNA) and interfering with initiation complex –> causes misreading of mRNA
broad bactericidal but primarily gram -
(cross outer mem via porin ch and cross inner by active transport)
transport is also oxygen dependent (inactive for anaerobes)
Give IV or IM —-has a polycationic charge –> poor absorption orally
low accumulation in CSF
synergistic with B lactams and has a post-antibiotic effect
chloramphenicol
binds to 50s and inhibits peptidyl transferase step of protein synthesis
only used for infections when benefit >risk of toxicity
broad bacteriostatic
bactericidal for h influenzae, strep pneumoniae, and N meningitidis
enters CNS and crosses placenta
erythromycin
a macrolide that binds 50s and inhibits the translocation step of protein synthesis
inactivated by gastic acid but absorbed by upper small intestine
streptogramins
streptogramin A and B
A binds nearby and induces a conformational change in the 50s subunit –> enhances B binding
B binds 50s and inhibits translocation step (same site at macrolides)
USE FOR vancomycin resistant e faecium or multidrug resistant gram + orgs
clindamycin
a lincosamide that binds the P and A sites in the 50s and suppresses protein synthesis
effective for macrolide resistant strains and against anaerobes
goes to bone and crosses placenta but not CNS
nitrofurantoin
many actions: causes DNA damage, and also inhibits ribosomal proteins and bacterial enzymes
USE ONLY FOR UTI due to e coli, s aureus, and e faecalis
not effective for acinetobacter, peudomonas, or proteus
bacteria have what type of ribosome?
70s
mammals have 80s
mechanisms of tetracycline resistance
decreased influx or acquisition of efflux pumps
decreased access to ribosome due to protecting proteins (TetO genes)
enzymatic inactivation of the drug (TetX gene)
side effects of tetracycline
GI –> pseudomembranous enterocolitis
teeth and bone issues in pregnant women and kids
Iv can cause venous thrombosis; IM can cause painful irritation
hepatic toxicity (liver accumulation)
photosensitivity
tigecycline resistance
it is a substrate for TetX –> bacterial strains with tetX gene are resistant
tigecycline is recommended for
interacts with
adults, not kids or pregnant women
warfarin and oral contraceptives
streptomycin is synergistic with…
B lactams
resistance against streptomycin
acquire inactivating enzymes (acetylases, adenylases, phosphorylases (plasmid encoded)
side effects of streptomycin
ototoxicity
nephrotoxocity
curare-like NM blockade –> respiratory peralysis
dermatitis and nerve dysfunction
chloramphenical crosses placenta…why cant infants process it?
it requires hepatic function for urine secretion)
chloramphenicol side effects
TOXIC
anemia
inhibits mammal 70s protein synthesis
gray baby syndrome - infant toxicity = vomiting, flaccid, hypothermia, resp. distress, gray pallor, and shock due to inadequate glucuronic acid conjugation or inadequate renal excretion
inhibiting CYP3A4 –> prolong drug half lives
antagonist to macrolides and clindamycin (competes for same binding site)
resistance to erythromycin (macrolide)
ATP efflux pump
methylase that modifies the ribosomal target = decreased drug binding
MLSb determinants: resistance to macrolides, lincosamides, and streptogramin B
hydrolysis by esterases
mutation of ribosome - specifically the 23 s rRNA to which the macrolides bind
side effects of erythromycin
GI motility cholestatic hepatitis cardiac arrhythmias (long QT with VT)
inhibits CYP3A4 and p450s –> MANY drug interactions
resistance to clindamycin
plasmid encoded MLSb
constitutive production of methylase
clindamycin side effects
modification of GI flora can lead to life threatening pseudomembranous enterocolitis with c dificile overgrowth
can inhibit neuromuscular transmission
rashes common in HIV patients
side effects of streptogramins
infusion-related pain and phlebitis
arthralgias
myalgias
