Ch. 24 - Antibiotics Flashcards
(27 cards)
cell wall synthesis inhibition
penicillin
cephalosporins
carapenems
vancomycin
isoniazid
lysozyme (not an antibiotic)
DNA synthesis inhibition
sulfonamides
fluoroquinolones (ciproflaxin)
protein synthesis inhibition - 30s subunit
aminoglycosides
tetracyclines
protein synthesis inhibition - 50s subunit
chloramphenicol
macrolides
lincosamides (clindamycin)
streptogramins
oxazolidinones
RNA synthesis inhibition
rifampin
sulfanamides
SPECTRUM: broad
EFFECT: bacteriostatic
MECHANISM: competitive inhibition with PABA – inhibit folic acid synthesis
fluoroquinolones (ciproflaxin)
SPECTRUM: broad
EFFECT: bactericidal
MECHANISM: inhibit DNA gyrase
penicillin - natural (Penicillin G, Penicillin V)
SPECTRUM: narrow (Gram Positive)
EFFECT: bactericidal (in rapidly multiplying bacterial cells - infection); bacteriostatic (slowly multiplying cells)
MECHANISM: bind to PBP transpeptidase (competitive inhibitor); conformation mimics D-ala-D-ala of NAM penta-peptide; inhibit cross-linking
aminopenicillins (amoxicillin, ampicillin)
SPECTRUM: broad - Gram Positive, partial Gram Negative
EFFECT: bactericidal
combine with beta-lactamase inhibitors: bind to active site of beta-lactamse =
Amoxicillin + Clavulanic Acid = Augmentin
Piperacillin + Taxobactum = Zosyn
beta-lactamase
penicillinase
Inactivate penicillin
Hydrolyze bond in beta-lactam ring; convert to harmless pencilloic acid
cephalosporins (generations 1-4)
SPECTRUM: narrow to broad - enhanced Gram Negative in higher generations; Gen 4 both Gram Positive and Gram Negative ; broader than penicillins - longer lasting in body; fewer allergic rxns
EFFECT: bactericidal
MECHANISM: bind PBP; mimic D-ala-D-ala; disrupt cross links in peptidoglycan
more resistant to beta-lactamases due to conformational shape
Used when have penicillin allergy
cell membrane function inhibition
bacitracin
polymyxin
gramicidin
Carbapenems (meropenem, imipenem)
SPECTRUM: broad - Gram Positive and Gram Negative
EFFECT: bactericidal
MECHANISM: PBP; inhibit cross links in peptidoglycan
Structure makes highly resistant to beta-lactamase
Imipenem - degrades kidneys; administer with cilastatin = Primaxin
Antibiotic of last resort
Gut bacteria developing carapenems - no new antibiotic to combat resistance
Structure highly resistant to beta-lactamases
Drug of last resort
vancomycin
SPECTRUM: narrow - Gram Positive (too large to fit through porins to affect Gram Negative)
EFFECT: bactericidal
MECHANISM: inhibit cell wall mucopeptide synthesis – H bond with terminal D-ala-D-ala; transpeptidase cannot bind
VRSA: DalaDala to DalaDlac
Drug of last resort - MRSA, C.diff
isoniazid
SPECTRUM: narrow - mycobacterium
EFFECT: bacteriostatic
MECHANISM: inhibition of mycolic acid (fatty acid cell wall) in mycobacterium
Treatment of TB: isoniazid, rifampin, and ethambutol
lysozyme
not an antibiotic!
SPECTRUM: narrow - Gram Positive
EFFECT: bactericidal
MECHANISM: hydrolyze glycosidic bond (beta 1-4) between NAM and NAG; cleaved bond – break of peptidoglycan
bacitracin
SPECTRUM: narrow - Gram Positive
EFFECT: bactericidal
MECHANISM: interferes with NAM precursor transport through plasma membrane; binds to transport protein in cell membrane that would bind NAM precursor
bacitracin + polymyxin + neomycin = Neosporin
polymyxin
SPECTRUM: narrow - Gram Negative
EFFECT: bactericidal
MECHANISM: insert into cell membrane – increase permeability of cell membrane (increase osmotic pressure – cell lysis)
aminoglycosides
gentamycin, neomycin, streptomycin
SPECTRUM: narrow - Gram Negative
EFFECT: bactericidal
MECHANISM: bind to 30s subunit; inhibition of initiation complex; misreading of genetic code
Streptomycin - sometimes treatment for TB
Gentamycin - treatment against UTI
Neomycin - cuts/abrasions (bacitracin + polymyxin + neomycin = Neosporin)
tetracyclines
SPECTRUM: broad
EFFECT: bacteriostatic
MECHANISM: bind to 30s subunit; block attachment of aminoacyl tRNA (no initiation)
Benzene ring formation
Can destroy microbiota with prolonged used
Cause staining in teeth
Affects bone development - do not give to children and pregnant women
To treat infection diseases - rickettsia and chlamydia
chloramphenicol
SPECTRUM: broad - Gram Positive, Gram Negative, Rickettsia, Chlamydia
EFFECT: bacteriostatic
MECHANISM: bind to 50s subunit; misreading of the genetic code (inhibit peptide bond formation)
small molecule
only for life-threatening illnesses (toxicity limits use):
- Gray Syndrome: chloramphenicol accumulates in blood of newborns, toxic rxn, sudden breakdown of cardiovascular system
- aplastic anemia: bone marrow stops producing RBCs (bone marrow suppression
macrolides (erythromycin)
SPECTRUM: broad - Gram Positive infections
EFFECT: bacteriostatic
MECHANISM: bind to 50s subunit; inhibit chain elongation (blocks translocation)
useful antibiotic - very few side effects
to treat: primary atypical pneumonia (mycoplasma pneumonia, legionnaire’s disease)
for pts with penicillin allergy
lincosamides (clindamycin)
SPECTRUM: Gram Positive and anaerobic infections
EFFECT: bacteriostatic
MECHANISM: bind to 50s subunit; inhibit chain elongation (block ribosomal translocation)
Use against penicillin- resistant bacteria
limit use to serious infections: precipitates C. diff - eliminates competing organisms from GI; permit C.diff to overgrow the area
Pseudomembranous Colitis
from Clostridium difficile (C.diff)
membranous lesions cover intestinal wall
watery diarrhea, fever, dehydration
