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USMLE Antibiotics

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nenafeno's version from 2016-09-10 02:59

Antibiotic Uses

DrugQuestionAnswerNumberMnemonic
Penicillin - G and VNatural PenicillinS pneumoniae/pyogenes/Actinomyces/N meningitidis/Treponema pallidumneurosyphilis, pharyngitis, endocarditisLimited coverage
Gram+ cocci/gram+ rods/gram- cocci/spirochetes bactericidal
Nafcillin, oxacillin, dicloxacillinantistaphylococcal penicillinS aureus, MSSA, streptococcalendocarditis, skin and soft tissue infectionsImproved staph coverage (vs penicillin)
Amoxicillin (oral), ampicillin (IV)AminopenicillinsH influenzae/E coli/Listeria monocytogenes/Proteus mirabilis/Salmonella/Shigella (enterococci)/Streptococcistrep throat, otitis mediaSome gram negative coverage; susceptible to beta-lactamases
Ampicillin drug of choice for enterococci
Ampicillin/amoxicillin HELPSS kill enterococci
Ticarcillin/piperacillinAntipseudomonal penicillinsPseudomonas aeruginosa (common pathogen resistant to multiple abx)/streptococci/enterococci/Enteric gram negative rods (SPECKS)step down abx for pseudomonas infection because other GNR's that cause nosocomial infection will be resistant to themRetain gram positive activity of penicillins, antipseudomonal coverage! combines with beta lactamase inhibitors (ampicillin/sulbactam; amoxicillin/clavulanate; piperacillin/tazobactam; ticarcillin/clavulanate)
Susceptible to beta-lactamases; not antistaphylococcal
CephalosporinsOrganisms NOT coveredListeria/Atypicals (Chlamydia/Mycoplasma)/MRSA/Enterococci4LAME
1st gen CephalosporinsOrganismsProteus mirabilis/E coli/Klebsiella pneumoniae3PEcK
1st gen CephalosporinsExceptions to normal coverageCefazolin prevents S aureus/ceftaroline covers MRSA2N/A
2nd gen CephalosporinsOrganismsH influenzae/Enterobacter aerogenes/Neisseria/Proteus mirabilis/E coli/Klebsiella pneumoniae/Serratia marcescens7HEN PEcKS
CeftriaxoneOrganismsMeningitis/gonorrhea2N/A
CeftazidimeOrganismsPseudomonas1N/A
4th gen Cephalosporins (cefepime)OrganismsPseudomonas/gram+2N/A
AztreonamOrganismsGram- rods only1N/A
VancomycinOrganismsMRSA/enterococci/C difficile (for pseudomembranous colitis)3N/A
AminoglycosidesOrganismsSevere gram- rod1N/A
ChloramphenicolOrganismsMeningitis (H influenzae/N meningitidis/S pneumoniae)3N/A
ClindamycinOrganismsAnaerobic aspiration pneumonia/lung abscesses/oral infections (Bacteroides fragilis/Clostridium perfringns)2Clindamycin treats anaerobe above diaphrahm/metronidazole below
TetracyclinesOrganismsBorrelia burgorferi/M pneumoniae/Rickettsia/Chlamydia4Accumulates intracellulary
MacrolidesOrganismsAtypical pneumonias (Mycoplasma/Chlamydia/Legionella)/STD (Chlamydia)/gram+ cocci (strep in pen allergic)4N/A
SulfonamidesOrganismsGram+/- (Nocardia/Chlamydia)/UTI3N/A
TrimethoprimOrganismsUTIs/Shigella/Salmonella/PCP4N/A
FluoroquinolonesOrganismsGram- rods in UTI/GI/Pseudomonas/Neisseria/some gram+5N/A
MetronidazoleOrganismsGiardia/Entamoeba/Trichomonas/Gardnerella vaginalis/Anaerobes (Bacteroides/C difficile)/H pylori6GET GAP on the metro
IsoniazidOrganismsM tuberculosis1N/A
RifampinOrganismsM tuberculosis/H influenzae/Meningococcal prophyaxis3N/A
PyrazinamideOrganismsM tuberculosis1N/A
EthambutolOrganismsM tuberculosis1N/A
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Identification

DrugQuestionAnswerNumberMnemonic
PenicillinsIDPen G (IV/IM)/Pen V (oral)3N/A
Penicillinase resistant penicillinsIDOxacillin/nafcillin/dicloxacillin3N/A
AminopenicillinsIDAmpicillin/amoxicillin2N/A
AntipseudomonalsIDTicarcillin/piperacillin2N/A
1st gen CephalosporinsIDCefazolin/cephalexin2N/A
2nd gen CephalosporinsIDCefoxitin/cefaclor/cefuroxime3N/A
3rd gen CephalosporinsIDCeftriaxone/cefotaxim/ceftazidime3N/A
4th gen CephalosporinsIDCefepime1N/A
30S inhibitorsIDAminoglycosides/Tetracyclines2buy AT 30/CCEL at 50
50S inhibitorsIDChloramphenicol/Clindamycin/Erythromycin (macrolides)/Linezolid4buy AT 30/CCEL at 50
Beta Lactamase inhibitorsIDClavulanic Acid/Sulbactam/Tazobactam4CAST
MonobactamIDAztreonam1N/A
CarbapenemIDImipenem/meropenem2N/A
AminoglycosidesIDGentamycin/Neomycin/Amikacin/Tobramycin/Streptomycin5Mean aMINoglyocosides GNATS caNNOT kill anaerobes
TetracyclinesIDTetracycline/doxycycline/democycline/minocycline4N/A
SulfonamidesIDSulfamethoxazole (SMX)/sulfisoxazole/sulfadiazine3N/A
FluoroquinolonesIDCipro/nor/levo/o/spar/moxi/gatifloxacins/enoxacin/nalidixic acid9N/A
MacrolidesIDArithromycin/clarithromycin/erythromycin3N/A
LincosamideIDClarithromycin1N/A
Azoles (not antibiotics)IDFlu/keto/mi/itra/voriconazoles/clotrimazole6N/A
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Mechanisms

DrugQuestionAnswerNumberMnemonic
VancomycinMechanismInhibits cell wall peptidoglycan formation/binds D-ala D-ala1Pay back 2 D-alas for vandalizing/vancomycin
MacrolidesMechanism50S Translocation inhibition1maCROlide/eryTHROmycin/tranSLOcation
Lincosamide/ClindamycinMechanism50S Translocation inhibition1buy AT 30/CCEL at 50
ChloramphenicolMechanism50S Blocks peptidyl transferase1buy AT 30/CCEL at 50
TetracyclinesMechanism30S A site blocking1buy AT 30/CCEL at 50
LinezolidMechanism50S Blocks initiator tRNA binding/ribosome formation1buy AT 30/CCEL at 50
AminoglycosidesMechanism30S initiation complex formation1A initiates the alphabet
SulfonamidesMechanismPABA antimetabolites (at dihydropteroate synthase PABA to DHPA)1N/A
TrimethoprimMechanismPABA antimetabolites (at dihydrofolate reductase DHF to THF)1N/A
PyrimethamineMechanismPABA antimetabolites (at dihydrofolate reductase DHF to THF)1N/A
FluoroquinolonesMechanismInhibit DNA topoisomerase II/IV (II is gyrase)2N/A
MetronidazoleMechanismForms free radical toxic metabolites that damage DNA1N/A
IsoniazidMechanismDecrease synthesis of mycolic acids1N/A
RifampinMechanismInhibits DNA dependent RNA polymerase1Rifampin's 4 Rs (RNA polymerase/Revs up P450/Red-orange body fluids/Rapid resistance if used alone)
PyrazinamideMechanismUncertain/thought to acidify intracellular compartments where TB is engulfed1N/A
EthambutolMechanismBlock arabinosyltrasnferase/stops carbohydrate polymerization in myobacteria1N/A
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Toxicity

DrugQuestionAnswerNumberMnemonic
PenicillinToxicityHypersensitivity/hemolytic anemia2N/A
OxacillinToxicityHypersensitivity/interstitial nephritis2N/A
NafcillinToxicityHypersensitivity/interstitial nephritis2N/A
DicloxacillinToxicityHypersensitivity/interstitial nephritis2N/A
AmpicillinToxicityHypersensitivity/rash/pseudomembranous colitis3N/A
AmoxicillinToxicityHypersensitivity/pseudomembranous colitis2N/A
TicarcillinToxicityHypersensitivity1N/A
PiperacillinToxicityHypersensitivity1N/A
CephalosporinsToxicityHypersensitivity/Vit K deficiency/increases nephrotoxicity of aminoglycosides3N/A
AztreonamToxicityUsually nontoxic/occasional GI upset2N/A
ImipenemToxicityGI distress/skin rash/CNS toxicity (seizures)3N/A
MeropenemToxicityGI distress/skin rash/CNS toxicity (seizures)3N/A
VancomycinToxicityNephrotoxicity/Ototoxicity/Thrombophlebitis/diffuse flushing/red man sydrome5well tolerated in general/NOT many problems
AminoglycosidesToxicityNephrotoxicity/Neuromuscular blockade/Ototoxicity/Teratogen4Mean aMINoglyocosides GNATS caNNOT kill anaerobes
TetracyclinesToxicityGI distress/discoloration of teeth/inihibition of bone growth in children/photosensitivity/contraindicated in pregnancy5N/A
MacrolidesToxicityMotility issues/Arrhythmia (long QT)/Cholestatic hepatitis acute/Rash/eOsinophilia5MACRO
ChloramphenicolToxicityAnemia/aplastic anemia/gray baby syndrome (lack UDP glucuronyl transferase)3N/A
ClindamycinToxicityPseudomembranous colitis/fever/diarrhea3N/A
SulfonamidesToxicityHypersensitivity/hemolysis in G6PD deficient/nephrotoxic/photosensitive/kernicterus in infants5N/A
TrimethoprimToxicityMegaoloblastic anemia/leukopenia/granulocytopenia3TMP (Treats Marrow Poorly)
FluoroquinolonesToxicityGI upset/superinfection/skin rash/headache/dizziness/bones (tendonitis/rupture/cramps/myalgias)/long QT7lones hurt attachment to bones
MetronidazoleToxicityDisulfiram rxn w/alcohol/headache/metallic taste3N/A
IsoniazidToxicityNeurotoxicity/hepatotoxicity/lupus3INH Injures Neurons/Hepatocytes
RifampinToxicityHepatotoxic/P450 drug interactions/Orange body fluids (nonhazardous)3Rifampin's 4 Rs (RNA polymerase/Revs up P450/Red-orange body fluids/Rapid resistance if used alone)
PyrazinamideToxicityHepatotoxic/hyperuricemia2N/A
EthambutolToxicityOptic neuropathy (red green colorblindness)1N/A
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Resistance

DrugQuestionAnswerNumberMnemonic
AminoglycosidesResistanceTransferases inactivate via acetylation/phosphorylation/adenylation3N/A
TetracyclinesResistanceDecreased uptake/increased efflux by plasmid encoded pumps1N/A
MacrolidesResistanceMethylation of 23S rRNA (of 50S subunit) binding site1Macrolides methylation inactivated
ChloramphenicolResistancePlasmid encoted acetyltransferase inactivates1N/A
SulfonamidesResistanceAltered target enzyme1N/A
FluoroquinolonesResistanceChromosome encoded mutation of DNA gyrase/plasmid mediated proteins bind DNA gyrase and protect/efflux pumps3N/A
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Keys to Use

DrugQuestionAnswerNumberMnemonic
AminopenicillinsKey to useAmoxicillin>Ampicillin2Oral availability of amOxacillin
Ticarcillin/piperacillinKey to useUse with clavulanic acid1N/A
3rd gen CephalosporinsKey to useWhen other Beta Lactams are resisted1N/A
ImipenemKey to useCilastatin1Kills is Lastin with cilastatin
AminoglycosidesKey to useRequire O2 for uptake/ineffective against anaerobes1Mean aMINoglyocosides GNATS caNNOT kill anaerobes
MacrolidesKey to useIncreases serum concentration of theophyllines (oral anticoagulants)1N/A
TetracyclinesKey to useDon't take w/milk/antacids/iron/pregnancy4Divalent cations inhibit absorption
DemeclocyclineKey to useADH antagonist/Diuretic in SIADH/rarely used as antibiotic1N/A
TrimethoprimKey to useCombination with sulfonamides1N/A
FluoroquinolonesKey to useDon't take with antacid1N/A
MetronidazoleKey to useTriple therapy w/PPI/clarithromycin against H pylori1N/A
IsoniazidKey to useBacterial catalase peroxidase (KatG) must convert INH to active metabolite1N/A
RifampinKey to useRapid resistance if used alone1Rifampin's 4 Rs (RNA polymerase/Revs up P450/Red-orange body fluids/Rapid resistance if used alone)
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Guidelines for Treatment and Prophylaxis

DrugQuestionAnswerNumberMnemonic
M tuberculosisProphylaxisIsoniazid1N/A
M tuberculosisTreatmentRifampin/Isoniazid/Pyrazinamide/Ethambutol4RIPE for treatment
M avium intracellulareProphylaxisAzithromycin1N/A
M avium intracellulareTreatmentAzithromycin/Rifampin/Ethambutol/Streptomycin4N/A
M leprae tuberculoidTreatmentDapsone/rifampin2N/A
M leprae lepromatousTreatmentDapsone/rifampin/clofazimine3N/A
Meningococcal infectionProphylaxisCiprofloxacin/rifampin in children2N/A
GonorrheaProphylaxisCeftriaxone1N/A
SyphilisProphylaxisBenzathine penicillin G1N/A
Recurrent UTIsProphylaxisTMP/SMX2N/A
Endocarditis w/surgical/dental proceduresProphylaxisPenicllins1N/A
Pregant women w/GBSProphylaxisAmpicillin1N/A
Streptococcal pharyngitis in child w/prior rheumatic feverProphylaxisOral penicillin1N/A
Post surgical S aureusProphylaxisCefazolin1N/A
Gonococcal/chlamydial conjunctivitis in newbornProphylaxisErythromycin ointment1N/A
MRSATreatmentVancomycin1N/A
VRETreatmentLinezolid/streptogramins (quinupristin/dalfopristin)3N/A
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To Be Avoided in Pregnancy

DrugQuestionAnswerNumberMnemonic
SulfonamidesWhy to avoid in pregnantKernicterus (bilirubin induced brain dysfunction)1N/A
AminoglycosidesWhy to avoid in pregnantOtotoxic1N/A
FluoroquinolonesWhy to avoid in pregnantCartilage damage1N/A
ClarithromycinWhy to avoid in pregnantEmbryotoxic1N/A
TetracyclinesWhy to avoid in pregnantDiscolored teeth/inhibition of bone growth2N/A
RibavirinWhy to avoid in pregnantTeratogenic1N/A
GriseofulvinWhy to avoid in pregnantTeratogenic1N/A
ChloramphenicolWhy to avoid in pregnantGray Baby1N/A
MnemonicWhy to avoid in pregnantSulfonamides/Aminoglycosides/Fluoroquinolones/Clarithromycin/Tetracyclines/Ribavirin/Griseofulvin/Chloramphenicol8SAFeChildren Take Really Good Care
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Distinctive Side Effects

Question Answer
Optic neuropathy (red green colorblindness)Ethambutol
Vitamin K deficiencyCephalosporins
Red man syndromeVancomycin
Long QTMacrolides/fluoroquinolones
Gray babyChloramphenicol
Kernicterus in infantsSulfonamides
Orange body fluidsRifampin
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USMLE Antifungals and Antivirals