penicillins Flashcards
what are the three special structural features of penicillin ?
thiazolidine rinsg
b lactmase rings
side chains
what is the mechanism associated with bacteria cross linking their walls ?
transpeptidases ( penicillin binding proteins) cross link the peptidoglycans in cell walls
bind to alanine residues to lysine
what does penicillin bind to an what does this result in ?
transpeptidases
penicillin mimics a alanyl d alanayl residues
this means that the rate of the wall breakdown is greater than the rate of the wall formation
what type of ab is penicillin ?
bacteriocide
what are the nareual penicillins ?
penicillin G and VK ( oral )
what drug may be administered with natural penicillin in order to increase the levels of it ?
probenecid which is a gout drug
what are the mechanisms of resistance associated with natural penicillin ?
1- modified penicillin binding proteins
many bacteria modify this protein as with strep pneumonia (modified transpeptidases)
2- reduced bacterial cell penetration , as with gram negative bacteria ( poor penetration ) , may decrease number of porins
3- beta lactamase enzymes
which bacteria uses beta lactamases to protect against antibiotics ?
staph aureus
many gram negatives 3amatan
where is beta lactamases found ?
in the periplasm of gram negative bacteria
gram positive bacteria secret it and hence produce more
what are the drugs that inhibit beta lactamase enzyme ?
clavulanic acid
sulbactam
tazobactam
they are added to penicillin to increase covergae
what are the clinical uses of natural penicillin ?
strep pyogens
actinomyces
syphillus
what are the adverse effects of penicillins ?
1- hypersensitivity reaction , on 2nd exposure
2- steven johnson syndrome , may evolve to TEN
3- interstitial nephritis
4- hemolytic anemia
5- serum sickness
what type of immediate hypersensitivity reaction is associated with penicillin use ?
immediate rewaction - type 1 igE mediated hypersensitivity reaction usually within 1 hour of taking the drug
non immediate reaction - maculopapular rash , absence of systemic signs type 4 mediated reaaction
what type of penicillin is associated with non immediate hypersensitivity reaction ?
aminopenicillin
what is the most common clinical case scenario associated with maculopapular rash in penicillin ?
more common with viral infections
EBV pharyngitis where amoxicillin is given
what is the immune mechanism associated with with steven johnson and TEN and what antibiotics are known to trigger this reaction ?
CD8 t cells
sulphonamides
aminopenicillins
cephalosporins
what is the immune mechanism associated with penicillin induced interstitial nephritis ?
the drug acts as a hapten
type 4 HS reaction
T cells and mast cells are associated
what is the classic presentation of interstitial nephritis ?
fever
oliguria
increased BUN
eosinophils
WBC casts sterile pyuria
how can hemolytic anemia triggered by penicillin be detected , what type of hypersensitivity reaction is it ?
direct coombs test will be positive
type 4 hs reaction
what is the immune mechanism associated with serum sickness and what is the presentation ?
type 3 hypersensitivity reaction
complement activation
presents with urticaria fever arthritis and lymphadenopathy
list the immune reactions in association with penicillin :
type 1 - acute IgE anaphylaxis
type 2 - hemolysis IgG
type 3- serum sickness IgG
type 4 - T cells skin nephritis
diarrhea following antibiotic therapy ?
pseudomembranous colitis by c difficlie
what antibiotic is classically known to induce oseudomembranous colitis ?
clindamycin
may mimic a hypersensitivty reaction to prniciillin but isnt ?
jarisch herxheimer reaction
what are the penicillinase resistant penicillins ?
dicloxacillin
nafcillin
oxacillin
also known as antistaphylococcal penicillins
what are the common uses of penicillinase resistant penicillins ?
community acquired cellulitid
impetigo
staph endocarditis
what are the penicillanse sensitive penicliins ?
also called the amino penicillinase
these are the amoxicillins
aminopenicillins
ampicliins ( IV)
why do aminopenicillins have a wider spectrum ?
because they penetrate porin channels of gram negative bacteria
sensitive to beta lactamase enzymes
what diseases are treated with penicillinase sensitive penicillins ?
HHEELPSS
H pylori
H influenza
E coli
Enterococci
Listeria
Proteus
Salmonella
Shigella
what are the beta lactamase inhibitors ?
CAST
clavulanic acid
Avibactam
sulbactam
tazobactam
commonly used with aminopenicillins
if we need something polymicrobial or with a wide spectrum coverage ?
aminopenicillins with a beta lactamase inhibitor
what are the antipsuedomonal penicillins ?
piperacillins
what greater advantage do piperacillin have over aminopenicillins ?
greater porin channel penetration
