USMLE - Micro AntiMicrobials
These antibiotics — Penicillin, Methicillin, Ampicillin, Piperacillin, Cephalosporins, Aztreonam, and Imipenem — prevent bacterial cell wall formation by inhibiting peptidoglycan cross-linking, leading to cell lysis and death.
Blocks cell wall synthesis by inhibiting peptidoglycan cross-linking
Penicillin, Methicillin, Ampicillin, Piperacillin, Cephalosporins, Aztreonam, Imipenem
Key Terms
Blocks cell wall synthesis by inhibiting peptidoglycan cross-linking
Penicillin, Methicillin, Ampicillin, Piperacillin, Cephalosporins, Aztreonam, Imipenem
Blocks peptidoglycan synthesis
Bacitracin, Vancomycin
Inhibits Folic Acid Synthesis (involved in methylation)
Sulfonamides, Trimethoprim
Blocks DNA topoisomerase
Fluoroquinolones
Blocks mRNA synthesis
Rifampin
Damages DNA
Metronidazole
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| Term | Definition |
|---|---|
Blocks cell wall synthesis by inhibiting peptidoglycan cross-linking | Penicillin, Methicillin, Ampicillin, Piperacillin, Cephalosporins, Aztreonam, Imipenem |
Blocks peptidoglycan synthesis | Bacitracin, Vancomycin |
Inhibits Folic Acid Synthesis (involved in methylation) | Sulfonamides, Trimethoprim |
Blocks DNA topoisomerase | Fluoroquinolones |
Blocks mRNA synthesis | Rifampin |
Damages DNA | Metronidazole |
Blocks protein synthesis at 50S ribosome | Chloramphenicol, Macrolides, Clindamycin, Streptogamins (Quinupristin, dalfopristin), Linezolid |
Blocks protein synthesis at 30S ribosome | Aminoglycosides, Tetracycline |
Penicillin Names? Class? MoA Use? Bactericidal for... Tox Resistance | G (IV and IM), V (oral). β-lactam Antibiotic Binds PBP (transpeptidiases) and blocks its cross-linking of peptidoglycan Gram+, N meningitidis, T pallidum, Syphilis Bactericidal for Gram+ cocci, Gram+ rods, Gram- cocci, Spirochetes Hypersensitivity rxn, Hemolytic anemia β-lactamase cleaves β-lactam ring |
Penicillinase-Resistent Penicillins Names Spectrum MoA Use Tox | Oxacillin, Nafcillin, Dicloxacillin Narrow spectrum Same as penicillin but bulk R group blocks β-lactamase access S aureus (except MRSA) Hypersensitivity reaction. Interstitial nephritis |
Aminopenicillins Names? Spectrum? MoA Availability Use Tox Resistance | Ampicillin and Amoxicillin. Wide spectrum Same as penicillin. AmOxicillin has greater Oral availability “HELPSS kill Enterococci “ H influenzae, E coli, Listeria, Proteus, Salmonella, Shigella, Enterococci Hypersensitivity rxn, Ampicillin rash, Pseudomembranous colitis Penicillinase sensitive. Combine w/ Clavulanic acid to protect against β-lactamase |
Antipseudomonals Names MoA? Spectrum? Use Tox Resistance | Ticarcillin and Peperacillin Same as penicillin. Extended spectrum Pseudomonas and Gram- rods Hypersensitivity rxn Penicillinase. Use with Clavulanic acid |
β-lactamase Inhibitors | “CAST” Clavulanic Acid, Sulbactam, Tazobactam |
Cephalosporins MoA Resistance What does it do to bacteria What bacteria can in kill? Tox | β-lactam Less susceptible to penicillinase Does not kill “LAME” bugs Listeria, Atypicals (chlamydia, Mycoplasma, MRSA, Enterococci Ceftaroline covers MRSA Hypersensitivity, VitK deficiency. ↑ nephrotoxicity of aminoglycosides |
1st gen Cephalosporins Names Uses | Cefazolin, Cephalexin Gram+ cocci, Proteus, E coli, Klebsiella “PEcK” Cefazolin used prior to surgery to prevent S aureus wound infection |
2nd gen Cephalosporins Names Uses | Cefoxitin, Cefaclor, Cefuroxime Gram+ cocci, Haemophilus, Enterobacter aerogenes, Neisseria, Proteus, E coli, Klebsiella, Serratia “HEN PEcKS” |
3rd gen Cephalosporins Names Uses | Ceftriaxone, Cefotaxime, Ceftazidime Serous Gram- infections resistant to other β-lactam Ceftriazone: Meningitis and Gonorrhea Ceftazidime: Pseudomonas |
4th gen Cephalosporins Names Uses | Cefepime Pseudomonas and Gram+ |
Aztreonam MoA Resistance Use Tox | Monobactam. Prevents peptidoglycan cross-linking by binding PBP3 Resistant to β-lactamase Gram- rods only. No activity against Gram+ or anaerobes (pseudomonas) Used for penicillin allergy pts and those with renal insufficiency who cannot tolerate aminoglycosides Generally nontoxic. Possible GI upset. |
Carbapenems Names MoA Co-administration w/... Resistance Use Tox | Imipenem, Meropenem, Ertapenem, Doripenem Broad spectrum β-lactam. I is coadministered w/ Cilastatin (inhibitor of renal dehydropeptidase I) to ↓ inactivation of drug in renal tubules. M resistent to inactivation Resistent to β-lactamase Gram+ cocci, Gram- rods, and anaerobes Only used when all else fails or life threatening GI distress, Skin rash, CNS tox (seizures) |
Vancomycin MoA What does it do to bacteria? Use Tox Resistance | Inhibits cell wall peptidoglycan formation by binding D-ala D-ala portion of cell wall precursors Bactericidal Gram+ only. Multi-drug resistant organisms: MRSA, enterococci, C diff “NOT so bad” Nephrotoxic, Ototoxic, Thrombophlebitis (inflammation of a vein caused by a blood clot), Diffuse flushing - Red Man Syndrome (prevented by pretreatment with antihistamines and slow infusion rate) Mutation of 2nd D-ala to D-lac |
Protein Synthesis inhibitors | “Buy AT 30, CCEL (sell) at 50” 30S inhibitors: Aminoglycosides (bactericidal), Tetracyclines (bacteristatic) 50S inhibitors (bacteristatic): Chloramphenicol, Clindamycin, Erythromycin (macrolides), Linezolid (variable) |
Aminoglycosides Names What does it do to bacteria? MoA Uptake | “Mean GNATS caNNOT kill Anaerobes” Gentamicin, Neomycin, Amikacin, Tobramycin, Streptomycin Bactericidal Inhibits formation of initiation complex and causes misreading. Blocks translocation Needs O2 for uptake thus ineffective against anaerobes |
Aminoglycosides Use Tox Resistance | “Mean GNATS caNNOT kill Anaerobes” Severe Gram- rods. Synergistic w/ β-lactams. N for bowel surgery Nephrotoxic (esp w/ cephalosporins), Neuromuscular blockade, Ototoxic (esp w/ loops diuretics), Teratogen Transferase enzyme that inactivates the drug by acetylation, phosphorylation or adenylation |
Tetracylcines Names What does it do to bacteria? MoA Elimination Do not take w/ | Tetracycline, Doxycycline, Demeclocycline, Minocycline |
Tetracylcines Use Tox Contraindications Resistance | Borrelia burgdorferi, M pneumoniae, Rickettsia, and Chlamydia (accumulates in cells so good at killing last 2) |
Macrolides Names What does it do to bacteria MoA Use | Azithromycin, Clarithromycin, Erythromycin Bacteriostatic Blocks translocation ("macroSLIDES"). Binds 23S rRNA of 50S ribosome Atypical pneumonia (Mycoplasma, Chlamydia, Legionella), STDs (Chlamydia), Gram+ cocci (strep in pts allergic to penicillin) |
Macrolides Tox Resistance | "MACRO" |
Chloramphenicol What does it do to bacteria? MoA Use Tox Resistance | Bacteriostatic. Blocks peptidyltransferase at 50S |
Clindamycin What does it do to bacteria? MoA Use Tox | Bacteriostatic. Blocks peptide transfer (transpeptidation) at 50S ribosomal subunit |
Sulfonamides Names What does it do to bacteria? MoA Use Tox Resistance | Sulfamethoxazole (SMX), Sulfisoxazole, Sulfadiazine |
Bacterial DNA, RNA, and Protein Synthesis | PABA + Pteridine --> [Dihydropteroate Synthase] --> Dihydropteroic acid --> Dihydrofolic acid --> [Dihydrofolate reductase] --> THF --> N methylene THF --> Purines (DNA and RNA), Thymidine (DNA), and Methionine (proteins) |
Trimethoprim What does it do to bacteria? MoA Used w/ Use Tox | Bacteriostatic |
Fluoroquinolones Names What does it do to bacteria Co-administration MoA Resistance | Ciprofloxacin, Norfloxacin, Levofloxacin, Olfoxacin, Sparfloxacin, Moxifloxacin, Gatifloxacin, Enoxacin. Nalidixic acid (quinolone) |
Fluoroquinolones | Gram- rods of Urinary and GI tracts (including Pseudomonas), Neisseria, Some Gram+ organisms |
Metronidazole What does it do to pathogens? MoA Use Tox | Bactericidal. Antiprotozoal |
Antimycobacterial Drugs | Tuberculosis |
Isoniazid Activation MoA Use Tox | Bacterial catalase-peroxidase (KatG) converts INH into active metabolite ↓ synthesis of mycolic acids TB Neurotoxicity and Hepatotoxicity. Lupus VitB6 prevents neurotoxicity |
Rifampin MoA Use Tox | "4Rs" RNA pol, Revs up P450, Red/Orange fluid, Rapid resistance if used alone Inhibits DNA-dependent RNA pol TB. Delays resistance to dapsone in leprosy. Meningococcal prophylaxis and chemoprophylaxis in contacts of children with Haemophilus influenzae type B Hepatotoxic. Drug interactions (↑ P450). Orange body fluid |
Pyrazinamide MoA Use Tox | Acidifies intracellular environment TB Hyperuricemia, Hepatotoxic |
Ethambutol MoA Use Tox | ↓ carbohydrate polymerization of mycobacterium cell wall by blocking arabinosyltranferase |
Meningococcal infection prophylaxis | Ciprofloxacin or Rifampin (for children) |
Gonorrhea prophylaxis | Ceftriaxone |
Syphilis prophylaxis | Benzathine Penicillin G |
History of recurrent UTI prophylaxis | TMP-SMX |
Endocarditis with surgical or dental procedures prophylaxis | Penicillins |
Pregnant woman carrying GBS prophylaxis | Ampicillin |
Strep Pharyngitis in child with prior RF prophylaxis | Oral penicillin |
Post-surgical infection due to S aureus prophylaxis | Cefazolin |
Gonococcal or Chlamydial conjunctivitis in newborns prophylaxis | Erythromycin ointment |
HIV prophylaxis for CD4 less than 200 | TMP-SMX for Pneumocystis pneumonia | Aerosolized pentamidine used if pt cannot tolerate TMP-SMX but this may not prevent toxoplasmosis |
HIV prophylaxis for CD4 less than 100 | TMP-SMX for Pneumocystis pneumonia and Toxoplasmosis | Aerosolized pentamidine used if pt cannot tolerate TMP-SMX but this may not prevent toxoplasmosis |
HIV prophylaxis for CD4 less than 50 | Azithromycin for Mycobacterium avium complex |
Treatment of MRSA and VRE (enterococci)? | MRSA: Vancomycin |
Amphotericin B MoA Use Route Supplement Tox How to reduce tox? | Binds ergosterol forming pores in membrane |
Nystatin | Binds ergosterol forming pores in membrane | "Swish and swallow" for oral candidiasis (thrush). Topical for diaper rash or vaginal candidiasis |
Azoles Names MoA Use Tox | Fluconazole, Ketoconazole, Clotimazole, Miconazole, Itraconazole, Voriconazole |
Flucytosine | Inhibits DNA and RNA synthesis by conversion to 5FU by cytosine daminase |
Caspofungin, Micafungin | Inhibits cell wall synthesis by inhibiting β-glucan |
Terbinafine | Inhibits fungal enzyme Squalene Epoxide |
Griseofulvin MoA Where does it accumulate? Use Tox | Interferes to MT function disrupting mitosis |
Antiprotozoan Therapy | Pyrimethamine (toxoplasmosis), Suramin and Melarsoprol (Trypanosoma brucei), Nifurtimox (T cruzi), Sodium Stibogluconate (Leishmaniasis) |
Chloroquine MoA Resistance Use Tox | Blocks detoxification of Heme into Hemozoin. Heme accumulates and is toxic to Plasmodia |
Treatment for Plasmodia falciparum | Artemether/lumifantrine or Atovaquone/Proguanil |
Treatment for life-threatenting malaria | Quinidine (in US), Quinine (Elsewhere), Artisunate |
Anti-Helminthic Therapy | Mebendazole, Pyrantel Pamoate, Ivermectin, Diethylcarbamazine, Praziquantel (for flukes like Schistosoma) |
Zanamivir, Oseltamivir | Inhibits Influenza Neuraminidase decreasing release of progeny |
Ribavirin | Inhibits synthesis of Guanine by competitively inhibiting IMP dehydrogenase |
Acyclovir MoA Use Better version? Tox Resistance | Guanosine analog that inhibits viral DNA pol by chain termination |
Treatment for Herpes Zoster (Shingles) | Famciclovir |
Ganciclovir MoA Use Better version? Tox Resistance | Guanosine analog that inhibits viral DNA pol CMV Valganiciclovir is a prodrug with better bioavailability Leukopenia, Neutropenia, Thrombocytopenia, Renal toxicity Mutated CMV DNA pol or lack of viral kinase |
Foscarnet MoA Use Tox Resistance | Pyrophosphate analog. Viral DNA pol inhibitor |
Cidofovir MoA Use Half life Tox Co-administration | Inhibits viral DNA pol |
HAART | AIDS-defining illness, low CD4 (below 500), High vial load | 2 nucleoside RT inhibitors + 1 non-nucleoside RT inhibitor OR Protease inhibitor OR Integrase inhibitor |
Protease inhibitors | "Navir tease a protease" |
NRTI Names MoA Activation Uses Tox | "Have you DINED with my NUCLEAR family" |
NNRTIs Names MoA Activation Tox | Nevirapine, Efaverenz, Delavirdine |
Integrase Inhibitors | Raltegravir |
Interferons What is it? What produces it? MoA Use Tox | Glycoprotein synthesized by virus-infected cells. |
Antibiotics to avoid during pregnancy | "SAFe Children Take Really Good Care" Sulfonamides (Kernicterus), Aminoglycosides (Ototoxic), Fluoroquinolones (Cartilage damage), Clarithromycin (Embryotoxic), Tetrocycline (Discolored teeth, inhibition of bone growth), Ribavirin (teratogenic), Griseofulvin (Teratogenic), Chloramphenicol (gray baby) |
Killed Influenza Vaccine | Generates Abs to H preventing entry of viral particles into the cells |