Anti-Infectives and Immune Response Notes

Anti-Infectives (Week 9)

  • Chapters 8-13.

Therapeutic Actions of Anti-Infectives

  • Interfere with biosynthesis of the bacterial cell wall.
  • Prevent cells of the invading organism from using essential substances for growth and development.
  • Interfere with protein synthesis (e.g., some bacteria need protein to grow, and some antibiotics inhibit protein synthesis).

Signs & Symptoms of Infection

  • Fever.
  • Lethargy (tired/weak/lack of energy).
  • Elevated WBC (Normal WBC is approximately 4,500-11,000).
  • Classic signs of inflammation: redness, swelling, heat, and pain (e.g., cellulitis).

Antibacterials / Antibiotics

  • Antibacterial: Targets bacteria.
  • Antibacterials & Antimicrobials:
    • Substances that inhibit bacterial growth or kill bacteria and other microorganisms (microscopic organisms including fungi, protozoa, yeasts).
  • Antibiotics:
    • Chemicals produced by one kind of microorganism that inhibit the growth of or kill another.
    • A type of antimicrobial substance active against bacteria.

Goal: Human Response to Anti-Infectives

  • Goal of anti-infective treatment: reduction of the population of the invading organism.
  • Human immune response can then eliminate it.
  • Drugs that eliminate all traces of the invading pathogen might be toxic to the host.
  • Immune response involves complex interactions among chemical mediators, leukocytes, lymphocytes, antibodies, & locally released enzymes & chemicals.

Antibiotics

  • Defined as drugs used to treat infections caused by bacteria & other microorganisms.
  • Made in three ways:
    • By living microorganisms (natural).
    • By synthetic manufacture (semi-synthetic) [chemically derived from natural antibiotics].
    • Through genetic engineering (synthetic) [100% chemically made].
  • Semi-synthetic antibiotics are derivatives of natural antibiotics, acting against bacteria resistant to the original compound because they have been improved (e.g., Ceftriaxone AKA Rocephin, which is broad spectrum).
  • Spectrum:
    • Narrow spectrum: effective only for a few microorganisms; very specific metabolic pathway or enzyme.
    • Broad spectrum: interfere with biochemical reactions in many kinds of microorganisms.

Bacteria Classification

  • Gram-positive:
    • The cell wall retains a stain or resists decolorization with alcohol.
    • Associated with Respiratory Tract infections; example: Streptococcus pneumoniae.
  • Gram-negative:
    • The cell wall loses a stain or is decolorized by alcohol.
    • Associated with GI & GU tract.
    • Gram-negative bacteria have an outer layer (membrane) that protects them, making them more resistant to antibiotics.
    • Examples include Escherichia coli (E. coli), Salmonella, Hemophilus influenzae, and many bacteria that cause urinary tract infections, pneumonia, or peritonitis.
    • More harmful than gram-positive bacteria because of a hard, protective outer shell, making them more resistant to antibiotics and harder to kill.
  • Gram + & Gram -:
    • Gram + bacteria have a thick peptidoglycan layer & no outer lipid membrane, where Gram - bacteria have a thin peptidoglycan layer & have an outer lipid membrane.
    • Gram-negative bacteria are more resistant than Gram-positive bacteria.
  • Aerobic: Depend on O_2 for survival.
  • Anaerobic: Do not use O_2 to survive.
  • Peptidoglycan:
    • A rigid envelope surrounding the cytoplasmic membrane of most bacterial species consisting of sugars and amino acids that surrounds the bacterial cytoplasmic membrane

Prophylaxis

  • Example: 1 gram of Ancef AKA Cefazolin given prior to surgery or three doses after surgery, absent of an infection.
  • Situations for prophylaxis:
    • People traveling to an area where malaria is endemic.
    • Patients undergoing GI or GU surgery.
    • Patients with known cardiac valve disease, valve replacements, & other conditions requiring invasive procedures.

Antibacterials / Antibiotics

  • The goal of antibiotic treatment is to decrease the amount of bacteria, not eradicate all bacteria.
  • Bacteriostatic drugs (prevent reproduction):
    • Inhibit growth of bacteria / prevent reproduction.
    • Examples: Tetracycline & sulfonamides.
  • Bactericidal drugs (kill the cell):
    • Kill bacteria / kill the cell.
    • Examples: Penicillin’s & Cephalosporins.
    • Bactericidal drugs can lead to C. diff.

Drug Therapy Across the Lifespan

  • Children:
    • Use anti-infectives with caution; early exposure can lead to early sensitivity.
    • Controversy regarding antibiotic use for ear infections; habitual use may contribute to resistant strains.
    • Monitor hydration and nutritional status carefully due to increased susceptibility to GI and nervous system effects.
  • Adults:
    • Adults often demand anti-infectives for a