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Microbiology - Antibiotics

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pujomora's version from 2016-05-30 00:40

Antibiotic overview

Question Answer
Block cell wall synthesis by inhibition of peptidoglycan cross-linkingPenicillin, methicillin, ampicillin, piperacillin
cephalosporins
Aztreonam
imipenem
Block peptidoglycan sythesisBacitracin, vancomycin
Block nucleotide synthesis by inhibiting folic acid synthesis (methylation)Sulfonamides
Trimethoprim
Block DNA topoisomerasesFluoroquinolones
Block mRNA synthesisRifampin
Damage DNAMetronidazole
Block protein synthesis at 50S ribosomal subunitChloramphenicol
Macrolides
Clindamycin
Stretogramins
Linezolid
Block protein synthesis at 30S ribosomal subunitAminoglycosides
Tetracyclines
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B-lactams

Question Answer Column 3 Column 4 Column 5
PenicillinBinds transpeptidases and blocks cross-linking of peptidoglycan
Activates autolytic enzymes
Gram-positives and gram-negative cocci (N. meningitidis) and spirochetes (Treponema pallidum)Hpersensitivity rxns
Hemolytic anemia
Not penicillinase resistant
Oxacillin, nafcillin, dicloxacillinNarrow spectrum penicillinStaph aureus (not MRSA)Hypersensitivity rxns
Interstitial nephritis
Penicillinase resistant because of bulky R group that protects B-lactam ring
Amipicillin, amoxicillinExtended-spectrum penicillinampicillin/amoxicillin HELPSS kill enterococci
H. influenzae
E.coli
Listeria
Proteus
Salmonella
Shigella
Enterococci
Hypersensitivity rxns
Ampicillin rash
Pseudomembranous colitis
sensitive to penicillinase
Ticarcillin, piperacillinPenicillin, used with clavulanic acidPseudomonas spp. and gram negative rods (KEE, etc)Sensitive to penicillinase
B-lactamase inhibitorsCAST
Clavulanic Acid
Sulbactam
Tazobactam
1st Generation CephalosporinsPenicillinCefazolin, cephalexin
PEcK
Proteus mirabilis, E.coli, Klebsiella
Hypersensitivity rxns
Vitamin K deficiency
Inc. nephrotoxicity of aminoglycosides
Disulfiram like reaction
Less susceptible to penicillinases
2nd Generation CephalosporinsPenicillinCefoxitin, cefaclor, cefuroxime
HEN PEcKS
H. influenza
Enterobacter aerogenes
Neisseria spp.
Proteus mirabilis
E.coli
Klebsiella pneumoniae
Serratia marcescens
Hypersensitivity rxns
Vitamin K deficiency
Inc. nephrotoxicity of ahminoglycosides
Disulfiram like reaction
Less susceptible to penicillinases
3rd generation CephalosporinsPenicillinCeftriaxone, cefotaxime, ceftazidime
for serious gram-neg infxn resistant to other B-lactams
Ceftriaxone - meningitis and gonorrhea
Ceftazidime - Pseudomonas
Hypersensitivity rxns
Vitamin K deficiency
Inc. nephrotoxicity of amino-glycosides

Disulfiram like reaction
Less susceptible to penicillinases
4th Generation CephalosporinsPenicillinCefepime - Pseudomonas and gram-positive organismsHypersensitivity rxns
Vitamin K deficiency
Inc. nephrotoxicity
of amino-glycosides

Disulfiram like reaction
Less susceptible to penicillinases
AztreonamPrevents peptidoglycan cross-linking by binding to PBP3
Synergistic with aminoglycosides
Gram-negative rods only
For pts allergic to penicillin and with renal insufficiency
noneB-lactamase resistant
Imipenem/cilastatin, meropenemBroad-spectrum
Always given with cilastatin (inhibitor of renal dehydropeptidase I)
Gram-positive cocci, gram-negative rods, anaerobesGI distress
Skin rash
CNS toxicity (seizures)
Vancomycin(not a B-lactam)
Binds D-ala D-ala portion of cell wall precursors → inhibits cell wall peptidoglycan formation
Gram-positive serious infxns only
MRSA, enterococci and C. diff
NOT
Nephrotoxic
Ototoxic
Thrombophlebitis - diffuse flushing - red man syndrome - prevent with pretreatment antihistamines
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Protein synthesis inhibitors

Question Answer
Which ones are they?Buy AT 30, CCEL at 50
30S inhibitors: Aminoglycosides (bactericidal), Tetracyclines
50S inhibitors: Chloramphenicol, Clindamycin, Erthromyic (macrolides), Linezolid
AminoglycosidesGNATS: Gentamicin, Neomycin, Amikacin, Tobramycin, Streptomycin
Inhibit formation of initiation complex and cause misreading of mRNA
Blocks translocation
Requires O2
Used of: gram-negative rods & bowel surgery
Toxicity: Nephrotoxic, Ototoxic, neuromuscular blockade, teratogen
TetracyclinesBind to 30S and prevent aminoacyl-tRNA attachment
Use: Borrelia burgdorferi, M. pneumoniae, Rickettsia, Chlamydia (accumulates intracellularly)
Tox: GI distress, teeth discoloration, bone grown inhibition, photosensitivity, teratogen
MacrolidesTHROmycins
Blocks tracnslocation to inhibit protein synthesis (binds to the 23S rRNA of the 50S unit
Use: Atypical pneumonias: Mycoplasma, Chlamydia, Legionella
Tox: MACRO: Motility issues, Arrhythmia (prolonged QT), acute Cholestatic hepatitis, Rash, eOsinophilia
ChloramphenicolBlocks peptidyltransferase at 50S ribosomal subunit
Meningitis
Serious toxicities: anemia, aplastic anemia, gray baby syndrome
ClindamycinBlocks peptide transfer at 50S subunit
Use: Treats anaerobes above the diaphragm
Tox: pseudomembranous colitis, fever, diarrhea
SulfonamidesPABA antimetabolites inhibits dihydropteroate synthase
Use: UTIs, gram-positives, gram-negatives, nocardia, chlamydia
Tox: Hypersensitivity, hemolysis if G6PD deficient, nephrotoxic, photosensitivity, kernicterus in infants, displaces other drugs from albumin
TrimethoprimInhibits bacterial DHFreductase
Use: with sulfonamides - UTIs, Shigella, Salmonella, Pneumocystis jirovecii
Tox: megaloblastic anemia, leukopenia, granulocytopenia (Treats Marrow Poorly)
Fluoroquinolones"floxacins"
Inhibits DNA gyrase (topoisomerase II and IV)
Don't take with antacids
Use: gram-negative rods in GI/GU tracts
Tox: cartilage damage (achilles tendon rupture), GI, superinfxns, skin rashes, HA
Prolong QT interval
MetronidazoleForms free radical toxic metabolites in the bacterial cell that damage DNA
Use: GET GAP: H. pylori, Anaerobes, Giardia, Gardnerella vaginalis, Entamoeba, Trichomonas
Tox: don't take with alcohol, HA, metallic taste
Dislfuram like reaction
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Antimycobacterial drugs

Question Answer
IsoniazidDecreases synthesis of mycolic acids need activation by catalase peroxidase enzyme
Use: prophylaxis against TB (only drug used alone for TB ppx)
Neuro (prevented with B6), hepatotoxic, lupus
Inhibits P450
RifampinInhibits DNA-dependent RNA polymerase
Use: TB, leprosy, H. influenza
Tox: Revs up P-450, red/orange body fluids
PyrazinamideTB
Works within macrophage phagolysosomes - requires acidic environment
Tox: hyperuricemia, hepatotoxic
Ethambutol↓ carbohydrate polymerizaction of mycobacterium cell wall by blocking arabinosyltransferase
TB
Tox: optic neuropathy (red-green color blindness)
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