Antibiotics and Patient Factors Quiz

Patient Factors

• Age:

  • Liver enzyme maturity affects drug metabolism
  • Newborns are susceptible to specific adverse effects
  • Elderly have reduced renal function

• Host Defence Status:

  • Impaired host defense requires higher doses and stronger antibiotics
  • Bactericidal vs. bacteriostatic antibiotic action is important

• Site of Infection:

  • Key factor in antibiotic choice
  • Normal flora and historical invading organisms influence selection
  • Presence of pus, necrotic tissue, clots, or an anaerobic environment influence choice
  • Infections in the brain must cross the blood-brain barrier (BBB)

• Hepatic Function:

  • Impairment can lead to toxic drug levels

• Renal Function:

  • Impairment leads to higher plasma levels and potential toxicity
  • Avoid specific antibiotics in renal impairment
  • Dose adjustments are necessary for some antibiotics

• Allergy:

  • History of allergy is crucial in antibiotic selection

Microbe Factors

• Culture Report:

  • Guides choice of therapy whenever possible

• Empiric Therapy:

  • Covers likely pathogens with combination therapy or broad-spectrum antibiotics
  • Used when the causative organism is unknown
  • Choice based on site of infection and known organisms at that site

• Definitive Therapy:

  • Used after identification of the causative organism

Drug Factors

• Efficacy and Spectrum:

  • Effective against target organism
  • Narrow or broad spectrum
  • Bactericidal if host defense is weak

• Minimal Inhibitory Concentration (MIC):

  • Lowest concentration that inhibits microbial growth
  • Therapeutic concentrations are above the MIC for effective bacterial reduction

• Minimal Bactericidal Concentration (MBC):

  • Lowest concentration that kills the organism
  • Often 2-8 times higher than the MIC

• Dose, Duration, Safety, and Compliance:

  • Consider dosage, duration of therapy, potential side effects, and patient adherence

• Route of Administration:

  • Oral, intravenous, or topical depending on the drug and infection

• Cost:

  • Economic considerations for treatment

Adverse Effects

• Dose-dependent:

  • Higher doses increase the chance of adverse effects

• Antibiotic Concentration:

  • High levels in the body can increase toxicity

• Drug Properties:

  • Certain antibiotics are more likely to cause specific side effects

• Host Flora:

  • Disruption of normal gut bacteria can lead to complications

Other Factors in Microbial Therapy

• Concentration-dependent Killing:

  • Aminoglycosides and fluoroquinolones require high concentrations for efficacy

• Time-dependent Killing:

  • Beta-lactams and glycopeptides require sustained levels above the MBC over dosing period

• Post-antibiotic Effect (PAE):

  • Bacterial growth remains suppressed even after antibiotic removal
  • Often concentration-dependent
  • Aminoglycosides and fluoroquinolones exhibit PAE against gram-negative bacteria

Combination of Antimicrobials

• Rationale:

  • Synergism: Combining bactericidal drugs based on disease
  • Treatment of Mixed Infections: Expanding coverage for multiple organisms
  • Preventing Resistance: Used for infections like tuberculosis and leprosy
  • Reducing Adverse Effects: Lower doses with each drug to decrease risks

• Advantages:

  • Initial Treatment of Severe Infections: Broad coverage for various pathogens
  • Preventing Resistance: Combating resistant strains

• Disadvantages:

  • Toxicity: Increased potential from multiple drugs
  • Resistant Strains: Selection for resistant bacteria
  • Multiple Drug Resistance: Development of multidrug-resistant bacteria
  • Cost of Therapy: Financial implications

Antibiotic Resistance

• Definition:

  • Bacteria are resistant to antibiotics, even at maximal tolerated doses

• Mechanisms:

  • Innate Resistance: Naturally resistant due to drug mechanisms
  • Acquired Resistance: Develops through mutations, plasmids, or enzymatic changes
  • Examples: Beta-lactamase production by Staphylococcus leads to resistance

Bacterial Classification

• Stain:

  • Gram-positive or gram-negative based on cell wall structure

• Shape:

  • Bacilli (rod-shaped), cocci (spherical), spirochetes (spiral-like)

• Oxygen Requirements:

  • Aerobes (require oxygen)
  • Anaerobes (do not require oxygen)

• Growth Requirements:

  • Nutritional and environmental factors

• Enzyme Production:

  • Catalase (produces oxygen bubbles)
  • Coagulase (clotting of plasma)
  • Beta-lactamase (inactivates beta-lactam antibiotics)

Bacterial Identification

• Gram Stain:

  • Gram-positive bacteria retain violet stain after decolorization
  • Gram-negative bacteria lose the violet stain and are counterstained with safranin

• Shape:

  • Bacilli (e.g., Haemophilus bacilli)
  • Cocci (e.g., Streptococci, Staphylococci)
  • Spirochetes (e.g., Treponema pallidum)

• Oxygen Requirement:

  • Aerobes: Require oxygen for growth
  • Anaerobes: Do not require oxygen for growth

Intracellular Pathogens

• Live within host cells, protected from the immune system
• Examples: Chlamydiae, Mycoplasmas, Legionella pneumophila, Mycobacterium tuberculosis

Protective Barriers in the Body

• Physical Barriers:

  • Skin and mucous membranes
  • Nose hairs
  • Airway mucus
  • Cilia

• Chemical Barriers:

  • Gastric acid
  • Lysozyme (tears and saliva)

Medically Important Bacteria

• Gram-Positive Cocci:

  • Staphylococci: Form pus and cause infections like boils, skin abscesses, and pneumonia
  • Streptococci: Cause a wide range of infections such as pharyngitis, pneumonia, and skin infections
  • Enterococci: Cause urinary tract and wound infections
  • Bacillus anthracis: Causes anthrax

• Gram-Negative Cocci:

  • Neisseria gonorrhoeae: Causes gonorrhea
  • Neisseria meningitidis: Causes meningitis

• Gram-Positive Bacilli:

  • Clostridium: Produce toxins and cause tetanus, botulism, and gas gangrene
  • Listeria monocytogenes: Causes foodborne illness
  • Corynebacterium diphtheriae: Causes diphtheria

• Gram-Negative Bacilli:

  • Escherichia coli: Causes urinary tract infections, diarrhea, and sepsis
  • Salmonella: Cause foodborne illness, typhoid fever
  • Shigella: Cause dysentery
  • Haemophilus influenzae: Causes meningitis, pneumonia, and ear infections
  • Pseudomonas aeruginosa: Opportunistic infection in immunocompromised patients
  • Klebsiella pneumoniae: Cause pneumonia and urinary tract infections
  • Yersinia pestis: Causes plague
  • Vibrio cholerae: Causes cholera
  • Helicobacter pylori: Causes gastritis and peptic ulcers