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Essential Antibiotic Guide: A Comprehensive Overview

Dive into the world of antibiotics in just 30 minutes with Dr. George Smulian! Learn about organism classification, antibiotic classes, mechanisms of action and resistance, toxicities, and more. Understand the crucial details to enhance your knowledge.

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Essential Antibiotic Guide: A Comprehensive Overview

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  1. All About Antibiotics!(in 30 minutes) George Smulian, MD

  2. Outline • Review of organism classification • Antibiotic review by classes • Antibiotic mechanisms of action • Antibiotic mechanisms of resistance • Antibiotic toxicities • Questions

  3. Organism classification: Gram stain Gram-positive bacteria: thick peptidoglycan layer (50–90% of cell envelope) Gram-negative bacteria: thinner peptidoglycan layer (10% of cell envelope)

  4. Organism classification: Gram-positive cocci Chains/pairs: Streptococcus sp., Micrococcus, Peptostreptococcus, Aerococcus, Enterococcus Clusters: Staphylococcus sp. Diplococci: Streptococcus pneumoniae

  5. Organism classification: Gram-positive rods (bacillus) Clostridium, Bacillus, Lactobacillus Filamentous: Nocardia, Actinomyces Coccobacillus: Propionibacterium, Corynebacterium, Listeria, Gardnerella

  6. Organism classification: Gram-negative cocci Neisseria, Moraxella, Veillonella Diplococci: Neisseria meningitidis in CSF

  7. Organism classification: Gram-negative rods (bacillus) Coccobacillus: Haemophilus, Gardnerella, Chlamydia Enterobacteriaceae (Proteus, Citrobacter, Escherichia coli, Klebsiella, Morganella, Providencia, Salmonella, Serratia, Shigella), Pseudomonas,Bacteroides, Prevotella, Fusobacterium, Capnocytophaga Curved: Campylobacter, Helicobacter, Vibrio

  8. Beta-lactam Antibiotics *Red denotes anti-pseudomonal activity Penicillins Cephalosporins 1st generation Cefazolin Cephalexin Cefadroxil 2nd generation Cefaclor Cefprozil Cefuroxime Cefotetan Cefoxitin 3rd generation Cefdinir Cefixime Cefotaxime Cefpodoxime PO Ceftazidime (IV) Ceftibuten Ceftriaxone Cefditoren 4th generation Cefepime (IV) 5th generation Ceftaroline • Penicillin – VK and G • Aminopenicillins • Amoxicillin • Ampicillin • Penicillinase stable • Dicloxacillin • Nafcillin • Oxacillin • Beta lactam/beta lactamase inhibitor • Amoxicillin-clavulanate • Ampicillin-sulbactam • Piperacillin-tazobactam (IV)

  9. Beta-lactam Antibiotics *Red denotes anti-pseudomonal activity Carbapenems Beta lactam/beta lactamase inhibitors Ceftazidime-avibactam Ceftolozane-tazobactam (Used to keep carbapenem potency) • Imipenem-cilistatin • Meropenem • Meropenem-vaborbactam • Doripenem • Ertapenem Monobactam • Aztreonam

  10. Gram-Specific Antibiotics *Red denotes anti-pseudomonal activity Gram-positive Activity Aminoglycosides Amikacin Gentamycin Tobramycin Neomycin Streptomycin Polymixins Colistin Polymixin B Gram-negative Activity • Glycopeptide • Vancomcyin • Lipoglycopeptides • Telavancin • Oritavancin • Dalbavancin • Lipopeptides • Daptomycin • Oxazolidinones • Linezolid • Tidezolid • Streptogrammins • Quinupristin-dalfopristin

  11. Additional Antimicrobials *Red denotes anti-pseudomonal activity Fluoroquinolones Macrolides Azithromycin Clarithromycin Erythromycin • Ciprofloxacin • Levofloxacin • Delafloxacin • Moxifloxacin • Ofloxacin • Miscellaneous • • Trimetheprim-sulfamethoxazole • • Dapsone • • Clindamycin • • Metronidazole • • Nitrofurantoin • • Fosfomycin • • Fidoxamycin • • Rifampin • • Chloramphenicol • Tetracyclines • • Minocycline • • Doxycycline • • Tigecycline

  12. Antibiotic Mechanisms of Action Nucleic Acid Synthesis Cell Wall Synthesis Folate Synthesis Sulfonamides Trimetheprim DNA Binding/Disruption Metronidazole Nitrofurantion Beta-lactams Penicillins Cephalosporins Carbapenems Monobactam DNA Gyrase Fluoroquinolones THF A RNA Polymerase Rifampin Fidoxamicin Glycopeptides Vancomcyin Talavancin Dalbavancin Oritavancin DHF A PABA 50S 50S subunit Macrolides Clindamycin Linezolid/Tidezolid Chloramphenicol Streptogramins 30S Cell Membrane Polymixins Daptomycin Fosfomycin (This column is bactericidal!) 30S subunit Tetracyclines/Tigecycline Aminoglycosides Protein Synthesis

  13. Mechanism of Action: Beta-lactams β-lactam NAGA NAMA NAGA NAMA NAMA NAGA NAMA G G Peptide side chain G G PBP G G G G NAGA NAMA NAGA NAMA NAMA NAGA NAMA G Peptide side chain X G Cell Wall Synthesis G G G G G G PBP: Penicillin-binding protein NAMA: N-acetylmuramic acid NAGA: N-acetylglucosamine disaccharide G: glycine bridge β-lactam PBP

  14. Mechanism of Action: Vancomcyin Vancomycin NAGA NAMA NAGA NAMA NAMA NAGA NAMA G G Peptide side chain G G PBP G G G G NAGA NAMA NAGA NAMA NAGA NAMA -- D-alanine Vancomycin -- D-alanine G X G Cell Wall Synthesis G G PBP PBP: Penicillin-binding protein NAMA: N-acetylmuramic acid NAGA: N-acetylglucosamine disaccharide G: glycine bridge

  15. Mechanism of Action: Fluoroquinolones Topoisomerase IV DNA Quinolones Transcription DNA Gyrase mRNA Translation Quinolones DNA X X X Protein Cell Death DNA Gyrase Topoisomerase IV Nucleic Acid Synthesis

  16. Mechanism of Action: Sulfa Drugs Trimethoprim-Sulfamethoxazole TFA DFA PABA Trimethoprim DNA X X TFA DFA PABA Nucleic acid Synthesis PABA: para-aminobenzoate DFA: Dihydrofolic acid TFA: Tetrahydrofolic acid Sulfamethoxazole DNA

  17. Mechanism of Action: Macrolides (50S) Macrolides Bacterial ribosome Polypeptide chain 50S mRNA 30S tRNA Bacterial ribosome Polypeptide chain X 50S mRNA Macrolides 30S tRNA Protein Synthesis

  18. Mechanism of Action: Tetracyclines30S Tetracyclines Bacterial ribosome Polypeptide chain 50S mRNA 30S tRNA Bacterial ribosome Polypeptide chain 50S mRNA 30S X tRNA Tetracyclines Protein Synthesis

  19. Mechanism of Action: Aminoglycosides Aminoglycosides Bacterial ribosome Polypeptide chain 50S mRNA 30S tRNA Bacterial ribosome Polypeptide chain mistranslation 50S mRNA 30S Protein Synthesis tRNA Aminoglycosides

  20. Antibiotic Mechanisms of Resistance Antibiotic Efflux pump Reduced permeability Outer membrane (Gram-negative) x Fluoroquinolones Macrolides Tetracyclines Porin Cell wall Carbapenems Inner membrane Beta-lactams x Inactivating enzyme Target site alteration Target site Resistance genes Plasmid Chromosome Beta-lactams Fluoroquinolones Modifying enzyme Aminoglycosides Transposon

  21. Mechanisms of Resistance: Beta-Lactams A. β-lactam NAGA NAMA NAGA NAMA β-lactam NAMA NAGA NAMA G Peptide side chain Resistance Gene: MecA (methicillin) X G G G PBP G G NAGA NAMA NAGA NAMA G G PBP: Penicillin-binding protein NAMA: N-acetylmuramic acid NAGA: N-acetylglucosamine disaccharide G: glycine bridge β-lactam NAMA NAGA NAMA X G G Peptide side chain G G PBP2a G G G G D. B. x Porin β-lactamases X Efflux pump C. Cytoplasma 21

  22. Resistance Genes: Beta-Lactamases • CTX-M & AmpC – extended-spectrum beta-lactamases • 3rd generation cephalosporin resistance • Inducible: Klebsiella, Enterobacter, Serratia sps. With 1st generation resistance • Carbapenemases • Class A • Klebsiella pneumoniae carbapenemase (KPC) • Serratia marcescens enzyme (SME) • Class B • New Delhi metallo-β-lactamse (NDM) • Verona integron–encoded metallo-β-lactamase (VIM) • Class D • Oxacillin-hydrolyzing (OXA-48) Modified Hodge Test Disc: Meropenem or Ertapenem Field: known susceptible E coli 1. Positive control 2. Negative control 3. Clinical isolate

  23. Mechanism of Resistance: Vancomcyin Vancomycin NAGA NAMA NAGA NAMA NAGA NAMA Vancomycin -- D-alanine -- D-alanine G G X G G NAGA NAMA NAGA NAMA PBP NAGA NAMA NAMA D-alanine -- Vancomycin X D-lactate -- G G Peptide side chain G G Cell Wall Synthesis PBP G G G G PBP: Penicillin-binding protein NAMA: N-acetylmuramic acid NAGA: N-acetylglucosamine disaccharide G: glycine bridge Resistance Gene: VanA 23

  24. Mechanisms of Resistance: Fluoroquinolones A. Quinolones Quinolones DNA X X X X DNA Cell Death X DNA Gyrase Topoisomerase IV Transcription Spontaneous Mutations DNA Gyrase mRNA Topoisomerase IV B. Efflux pump Translation Quinolones Protein Cytoplasma

  25. Mechanisms of Resistance: Macrolides Macrolides Bacterial ribosome Polypeptide chain X 50S Macrolides mRNA A. Enzyme-mediated binding site alteration B. Mutation of binding site 30S tRNA X Polypeptide chain 50S C. Efflux pump mRNA 30S Macrolides tRNA Cytoplasma

  26. Antibiotic Toxicities • Clostridium difficile infection • Penicillins • Allergies (3-10%): fever, rash, interstitial nephritis • Cephalosporins (5-10% cross-reactivity with penicillin allergies) • Neutropenia • Cefotetan – hypoprothrombinemia and disulfiram-like reaction • Ceftriaxone – biliary sludging • Carbapenems – seizures • Vancomcyin • Red-man syndrome • Hearing loss/tinnitus • Neutropenia

  27. Antibiotic Toxicities • Daptomycin – reversible myopathy • Chloramphenicol - marrow suppression/aplastic anemia • Colistin – nephrotoxicity • Aminoglycosides • Cochlear toxicity – high frequency loss • Vestibular toxicity – not related to dose/duration • Nephrotoxicity (proximal tubular necrosis) • Macrolides – QT prolongation • Tetracyclines • Dental enamel discoloration • Photo toxicity • Minocycline - Blue-black hyperpigmentation skin & mucous membranes

  28. Antibiotic Toxicities • Linezolid • Cytopenias • Serotonin syndrome • Sulfa drugs • Allergy – fever, rash (including Stevens-Johnson) • Cytopenias • AKI • Hyperkalemia • Quinolones • Cartilage abnormalities/tendon rupture • QT prolongation • Peripheral neuropathy • Metronidazole – peripheral neuropathy

  29. All of the following antibiotics impart cell death by disruption of the bacterial cell wall synthesis except: • Azithromycin • Aztreonam • Vancomycin • Piperacillin-tazobactam • Ceftriaxone

  30. Question 2 • 64 yo male with h/o DM, CAD s/p CABG and COPD. Five months ago, he was admitted with hypoxic respiratory failure and pneumonia requiring intubation. He failed several attempts at extubation and now has trach with ventilator dependence. He was transferred after his initial hospitalization to an LTACH for an attempt at vent weaning. Since that initial hospitalization he has been readmitted twice with concerns for VAP. With each hospitalization he has been treated with vancomycin and cefepime. He now presents with fever, mild hypotension and leukocytosis (wbc 16.3k with 89%N). Upon evaluation he appears chronically ill. He is on his baseline vent settings (FiO2 25% with 98% sat) and CXR/pulmonary secretions unchanged. He has a chronic indwelling Foley with cloudy urine in the bag. UA has TNTC wbc’s. The patient is initially started on cefepime but with continued fevers and hemodynamic instability his antibiotic is changed to meropenem. Initial blood cultures x 2 and urine culture grows Enterobacter cloacae which the microbiology lab reports is resistant to ertapenem and is Modified Hodge test positive.

  31. What is the most likely mechanism of resistance for this Enterobacter cloacae? • Induction of an efflux pump • Alteration of the antibiotic target site • Acquisition of resistance gene encoding a carbapenemase • Decreased membrane permeability • Intrinsic resistance

  32. Question 3 78 yo female with a h/o hypothyroidism and rate controlled afib. Three weeks prior to admission she underwent successful ablation of her afib and her medications were changed from amiodarone, metoprolol and levothyroxine to a lower dose of metoprolol and maintained on levothyroxine. She now presents 2 days after returning from a 10 day Caribbean cruise. She complains of SOB, DOE, a non-productive cough, fevers, chills and malaise. On evaluation she is hypoxic with 88% oxygen saturation on RA and tachypneic and struggles to complete full sentences. Pulmonary exam reveals diffuse rhonchi. Labs reveal wbc 18.5 N 78% L 30%, normal LFTs and renal profile. ABG on RA pH 7.36, pCO2 37, paO2 75, bicarb 24. She is started empirically of ceftriaxone and azithromycin for CAP and admitted to the ICU. Sputum cx revealed > 25 wbc, < 10 epis and scant normal flora. Urine pneumococcal antigen negative Urine legionella antigen positive

  33. Question 3 Hospital day 3 her rhythm strip shows:

  34. What is the most likely cause of the patient’s arrhythmia? • Cardiac ischemia due to hypoxia • QT prolongation • Electrolyte abnormalities • Acidosis • Underlying known cardiac arrhythmia

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