AB & AM Agents

• Antibacterial antimicrobial agents


  Chemical substances produced by various species of microorganisms or wholly or partially by chemical synthesis, which in low concentrations, inhibit the growth of other microorganisms
• Types of antimicrobial agents

  • Antibacterial agents
  • Antimycobacterial agents
  • Antifungal agents
  • Antiparasitic agents
• Modes of action of antibacterial antimicrobial agents

  • Interference with cell wall synthesis
  • Disruption of cell membrane
  • Inhibition of protein synthesis
  • Interference with nucleic acid synthesis
• Antibiotic


  Chemical substance produced by various species of microorganisms that is capable in small concentrations of inhibiting the growth of other microorganisms
• Semi-synthetic antibiotics


  Synthetic derivatives of naturally-occurring antibiotics
• Chemotherapeutic agents


  Chemical antimicrobial compounds
• Antimicrobial agent


  Chemical substance produced by a microorganism or wholly or partially by chemical synthesis, which in low concentrations, inhibits the growth of other microorganisms
• Bacteriostatic agents


  Antimicrobial agents that inhibit growth and replication of bacteria; are non-lethal
• Bactericidal agents


  Antimicrobial agents that cause bacterial cell death
• Selective toxicity


  Highly effective against the microbe but have minimal or no toxicity to humans
• Beta-lactam antimicrobial agents


  • Feature a ß-lactam ring in their structure
  • Act on the formation of the peptidoglycan layer
• Penicillin-binding proteins (PBPs)


  Enzymes that are the targets of ß-lactam antibiotics
• Beta-lactam antimicrobial agent mechanism


  1. Form an irreversible intermediate within active site of PBPs

  2. Weaken peptidoglycan layer

  3. Inhibit cell growth/lysis
• Types of beta-lactam antimicrobial agents

  • Penicillins
  • Cephalosporins
  • Cephamycins
  • Monobactams
  • Carbapenems
• Beta-lactamases


  Serine proteases that inactivate ß-lactam antimicrobial agents
• Classes of beta-lactamases


  • Class A (e.g. SHV-1, TEM-1)
  • Class B (zinc-dependent metalloenzymes)
  • Class C (cephalosporinases)
  • Class D (penicillinases)
• Extended-spectrum beta-lactamases (ESBLs)


  Produced by point mutations in Class A beta-lactamases, encoded on plasmids
• Beta-lactamase inhibitors


  • Reversible/irreversible binding to inactivate the enzyme
  • Irreversible "suicide inhibitors" that permanently inactivate the beta-lactamase
• Glycopeptides


  • Large molecules unable to penetrate the outer membrane of Gram-negative bacteria
  • Spectrum limited to Gram-positive organisms
  • Complex with the D-Ala-D-Ala portion of the cell wall precursor
• Glycopeptides


  • Vancomycin
  • Teicoplanin
  • Telavancin
• Bacitracin


  Targets Gram-positive bacteria, too toxic for systemic use
• Cycloserine


  Analogue of D-Alanine, produced by Streptomyces
• Fosfomycin


  Broad-spectrum antibiotic that targets the Mur enzyme
• Isoniazid


  Antibacterial antimicrobial agent
• Polymyxin B and Colistin (Polymyxin E)


  Act like cationic detergents to disrupt cell membranes, limited spectrum and significant toxicity
• Protein synthesis inhibitors


  • Aminoglycosides (e.g. streptomycin, neomycin, kanamycin, gentamicin, amikacin)
  • Tetracyclines (e.g. tetracycline, doxycycline, minocycline, tigecycline)
  • Macrolides (e.g. erythromycin, clarithromycin, azithromycin)
  • Chloramphenicol, Thiamphenicol
  • Lincosamides (e.g. lincomycin, clindamycin)
  • Oxazolidinones (e.g. linezolid)
  • Streptogramins (e.g. Quinupristin-dalfopristin)
• Aminoglycosides


  Block the initiation of translation and cause the misreading of mRNA
• Tetracyclines


  Block the attachment of tRNA to the ribosome
• Macrolides


  Prevent the continuation of protein synthesis
• Chloramphenicol


  Prevents peptide bonds from being formed
• Streptogramins


  Each interferes with a distinct step of protein synthesis
• Lincosamides


  Prevent the continuation of protein synthesis
• Oxazolidinones


  Interfere with the initiation of protein synthesis
• Sulphonamides


  Analogues of PABA, affect folic acid metabolism
• Diaminopyrimidines


  Prevent reduction of dihydrofolic acid to tetrahydrofolic acid
• Sulphonamides


  • Sulfamethoxazole
  • Sulfadoxine
  • Sulfadiazine
• Diaminopyrimidines


  • Trimethoprim
  • Pyrimethamine
  • Cycloguanil
• Quinolones


  Synthetic chemotherapeutic agents that target DNA gyrase and topoisomerase IV
• Quinolones


  • Nalidixic acid
  • Ciprofloxacin
  • Ofloxacin
• Nitroimidazoles


  Active only against anaerobic and certain microaerophilic bacteria