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Snapshot
  • A 45-year-old woman presents to urgent care for a large abscess on her forearm. She had fallen and scraped herself a few days ago with subsequent erosions and increasing redness and warmth of the area. Today, she noticed some drainage of pus. A wound culture was sent, and she is started on a cephalosporin for soft tissue infection.
Introduction
  • Drugs
    • see below
  • Clinical use
    • bacterial infections
 
Cell Wall Synthesis Inhibitors
Penicillins
(Bactericidal: inhibits bacterial cell wall synthesis via competitive inhibition of the transpeptidase enzyme)
Class Name of Drug(s) Indications
Penicillin 
  • Penicillin G
  • Aqueous (crystalline) penicillin G
  • Procaine penicillin G
  • Benzathine penicillin G
  • Penicillin V
  • S. pnuemoniae
  • S. pyogenes (group A strep)
  • N. meningitidis
  • T. pallidum
  • L. monocytogenes
  • A. israelii
  • P. multocida
Aminopenicillins 
  • Ampicillin
  • Amoxicillin
  • ↑ gram-negative coverage
  • Enterococci (group D strep)
  • All others listed above
Penicillinase-resistant penicillins 
  • Methicillin
  • Nafcillin
  • Oxacillin
  • Cloxacillin
  • Dicloxacillin
  • Penicillinase-producing S. aureus
  • All others listed above
Antipseudomonal penicillins 
  • Carbenicillin
  • Ticarcillin
  • Piperacillin
  • P. aeruginosa
  • Anaerobic bacteria
  • All others listed above
Cephalosporins
(Bactericidal: inhibits bacterial cell wall synthesis via competitive inhibition of the transpeptidase enzyme)
1st generation 
  • Cefazolin
  • Cephalexin
  • Gram-positives
  • Some gram-negatives
  • Skin infection prophylaxis
2nd generation
  • Cefoxitin
  • Cefaclor
  • Cefuroxime
  • Gram-positives
  • Improved gram-negative coverage
  • Anaerobes

3rd generation

  • Ceftriaxone
  • Cefotaxime
  • Ceftazidime
  • Serious gram-negative infections
  • Meningitis
  • Pseudomonas
4th generation
  • Cefepime
  • Same coverage as cephalosporins + expanded Pseudomonas coverage + expanded gram-positive coverage
5th generation
  • Ceftaroline
  • Expanded gram-positive and gram-negative coverage, non-suitable coverage of Pseudomonas
Other Cell Wall Inhibitors

Vancomycin
(bactericidal: inhibits bacterial cell wall synthesis by disrupting peptioglycan cross linking)

  • Vancomycin
  • MRSA
  • Patients with PCN or ceph allergies
  • S aureus
  • S epidermidis
  • C. difficile


Beta-lactamase inhibitors
(beta-lactamse inhibitors that  prevent the degradation of beta-lactam antibiotics)
  • Clavulanic acid
  • Sulbactam
  • Tazobactam
  • Gram-positive
  • S. aureus
  • S. epidermis
  • Gram-negative
  • E. coli
  • Klebsiella
Carbapenems
(Inhibits bacterial cell wall synthesis)
  • Imipenem (+ cilastatin)
  • Meropenem
  • Doripenem
  • Ertapenem
  • Broadest activity of any antibiotic (does NOT cover MRSA, Mycoplasma, and some Pseudomonas)
Aztreonam
(inhibits bacterial cell wall synthesis)
  • Aztreonam
  • Gram-negative rods
  • Aerobes
  • Difficult-to-treat hospital-acquired infections
Polymyxins 
  • Polymyxin B
  • Polymyxin E
  • Topical gram-negative infections
Bacitracin
  • Bacitracin
  • Topical gram-positive infections
Protein Synthesis Inhibitors
Anti-30S Ribosomal Subunit
Aminoglycosides
(bactericidal)
  • Gentamicin
  • Neomycin
  • Amikacin
  • Tobramycin
  • Streptomycin
  • Severe gram-negative infections
  • Aerobes only
Tetracycline
(bacteriostatic)
  • Tetracycline
  • Doxycycline
  • Minocycline
  • Demeclocycline
  • Chlamydia
  • Rickettsia
  • Bacteria without peptidoglycan cell walls
  • Spirochetes
  • V. cholerae
  • H. pylori
Anti-50S Ribosomal Subunit
Macrolides 
  • Erythromycin
  • Azithromycin
  • Clarithromycin
  • Outpatient URI, LRI
  • Atypical pneumonia
  • STDs
  • Gram-positive cocci
Chloramphenicol  
(bacteriostatic)
  • Chloramphenicol
  • H. influenzae
  • Bacterial meningitis
  • Brain abscess
  • Bacteroides fragilis
Clindamycin 
(bacteriostatic)
  • Clindamycin
  • Anaerobes above the diaphragm
  • Female GU
  • TSS
Linezolid
(
variable)
  • Linezolid
  • Resistant gram-positives (MRSA, VRE)
  • can cause serotonin syndrome 
Streptogramins
  • Quinupristin
  • Dalfopristin
  • VRE
  • GAS and S. aureus skin infections
  • Note: bacteriocidal when used together
DNA Synthesis Inhibitors
Fluoroquinolones
(Bactericidal: inhibit DNA gyrase enzyme, inhibiting DNA synthesis)
1st generation 
  • Nalidixic acid
  • Gram-negative UTIs
2nd generation 
  • Ciprofloxacin
  • Norfloxacin
  • Enoxacin
  • Ofloxacin
  • Levofloxacin
  • Gram-negative UTIs
  • Gram-negative GI tract
  • Pseudomonas
3rd generation 
  • Gatifloxacin
  • As above + gram-positives
4th generation 
  • Moxifloxacin
  • Gemifloxacin
  • As above + gram-positives + anaerobes
Other DNA Inhibitors
Metronidazole
(bacteridical: metabolic byproducts disrupt DNA)
  • Metronidazole (Flagyl)
  • Bacteria AND protozoa
  • Anaerobes below the diaphragm 
  • C. difficile
  • H. pylori
RNA Synthesis Inhibitors
Rifampin 
(bactericidal: inhibits RNA transcription)
  • Rifampin
  • TB
  • Leprosy
  • H. influenzae prophylaxis
  • Antistaphylococcal
Mycolic Acids Synthesis Inhibitors
Isoniazid 
  • Isoniazid
  • TB
  • Latent TB
Folic Acid Synthesis Inhibitors
Sulfonamides 
  • Sulfamethoxazole (SMX)
  • Sulfisoxazole
  • Sulfadiazine
  • Respiratory (S. pneumoniae, H. influenzae)
  • GI (enterics)
  • UTIs
  • PCP and T. gondii
Trimethoprim 
  • Trimethoprim
  • See Sulfonamides
Pyrimethamine 
  • Pyrimethamine
  • Malaria
  • T. gondii
Miscellaneous   
Drugs Mechanism of Action Indications and Side Effects
Pyrazinamide
  • Uncertain mechanism: potentially accumulates in cells dsirupting membrane potential and fatty acid synthesis
  • Part of RIPE therapy for TB
  • Can cause hyperuricemia and hepatoxicity
Ethambutol
  • Inhibits arabinosyltransferase (inhibiting production of mycobacterium cell wall)
  • Part of RIPE therapy for TB and used for M. avium-intracellulare
  • Can cause optic neuropathy (red-green color blindness)
Daptomycin
  • Lipopeptide that disrupts cell membrane
  • Multi-resistant gram-positives such as MRSA and VRE
  • Can cause myopathy (elevated CK and rhabdomyolysis
  • Ineffective in lung infections as drug cannot distinguish between surfactant lipid layer and bacterial membranes, thus is sequestered in surfactant

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