PPT 3

• Bactericidal agents

  Kill bacteria
• Bacteriostatic agents


  Arrest the growth of bacteria
• Narrow-spectrum antimicrobial agents

  Target specific types of microorganisms
• Broad-spectrum antimicrobial agents


  Target a wide range of microorganisms
• Mechanisms of bacterial resistance to antimicrobial agents

  • Inactivation of the antimicrobial agent
  • Alteration of the antimicrobial target
  • Decreased uptake of the antimicrobial agent
  • Increased efflux of the antimicrobial agent
• MRSA


  Methicillin-resistant Staphylococcus aureus
• MRSE

  Methicillin-resistant Staphylococcus epidermidis
• β-lactam ring


  Structural component of β-lactam antibiotics
• β-lactam antibiotics

  Antibiotics that contain a β-lactam ring
• β-lactamase


  Bacterial enzyme that destroys the β-lactam ring
• Actions to help in the war against drug resistance

  • Prescribe antimicrobial agents judiciously
  • Avoid unnecessary use of antimicrobial agents
  • Ensure proper dosing and duration of antimicrobial therapy
  • Implement effective infection control measures
  • Develop new antimicrobial agents
  • Educate healthcare providers and the public about antimicrobial resistance
• Empiric therapy

  Antimicrobial treatment initiated before the causative pathogen is identified

  
• Factors considered before prescribing an antimicrobial agent


  • Suspected pathogen
  • Antimicrobial susceptibility patterns
  • Patient's medical history
  • Patient's age and weight
  • Severity of the infection
  • Potential for adverse effects
• Undesirable effects of antimicrobial agents

  • Selection of resistant organisms
  • Allergic reactions
  • Toxicity
• Superinfection


  Overgrowth of microorganisms that are resistant to the antimicrobial agent(s) being used
• Diseases that can result from superinfections

  • Yeast vaginitis
  • Clostridium difficile infection
  • Antibiotic-associated diarrhea
• Synergism


  Antimicrobial agents that work together to enhance their effectiveness
• Antagonism


  Antimicrobial agents that work against each other, reducing their effectiveness
• Paul Ehrlich, the Father of Chemotherapy, was a German chemist who began searching for "magic bullets" that would destroy bacteria without damaging normal body cells
• Alexander Fleming invented the first antibiotic, penicillin

  
• Penicillin and cephalosporins are produced by molds, while bacitracin, erythromycin, and chloramphenicol are produced by bacteria

  
• Penicillin interferes with the synthesis and cross-linking of peptidoglycan, inhibiting cell wall synthesis
• Penicillin does not destroy human cells because human cells do not have cell walls

  
• Antiprotozoal agents are usually quite toxic to the host, either by interfering with DNA and RNA synthesis or by interfering with protozoal metabolism
• The first antiviral agent effective against HIV was zidovudine (AZT), introduced in 1987
• Superbugs are strains of bacteria, viruses, parasites and fungi that are resistant to most of the antibiotics and other medications commonly used to treat the infections they cause
• MRSA and MRSE are resistant to all anti-staphylococcal drugs except vancomycin and one or two more recently developed drugs
• Vancomycin-resistant Enterococcus spp. (VRE) are resistant to most anti-enterococcal drugs, including vancomycin
• Multidrug-resistant M. tuberculosis (MDR-TB) is resistant to the two most effective first-line therapeutic drugs, isoniazid and rifampin

  
• Selecting for resistant organisms is an undesirable effect of antimicrobial agents, where the resistant ones survive while the susceptible ones die

  
• Penicillin G in low doses can sensitize patients prone to allergies, leading to severe reactions like anaphylactic shock or hives upon subsequent exposure
• Cephalosporins are β-lactam drugs produced by molds that interfere with cell wall synthesis and are bactericidal
• Tetracyclines are broad-spectrum, bacteriostatic drugs that inhibit the 30S ribosomal subunit, hindering the binding of aminoacyl-tRNA
• Aminoglycosides are broad-spectrum, bactericidal drugs that inhibit protein synthesis and are effective against aerobic Gram-negative bacteria
• Macrolides are bacteriostatic at lower doses but bactericidal at higher doses, inhibiting protein synthesis
• Fluoroquinolones are bactericidal drugs that inhibit DNA synthesis
• Multidrug therapy is used when a single antimicrobial agent is not sufficient to destroy all the pathogens, with two or more drugs used simultaneously
• Mechanisms of action of antifungal agents

  • Binding with cell membrane sterols
  • Interfering with sterol synthesis
  • Blocking mitosis or nucleic acid synthesis
• Many antimicrobial agents are toxic to humans, with some like chloramphenicol and streptomycin causing severe side effects
• Superinfections are population explosions of microorganisms that are resistant to the antibiotic(s) being used