Principles of Antimicrobial Therapy Flashcards
Relationships in an Infected Patient
- Who are involved
- Hosts
- Pathogen
- Antibiotic
- Commensals
Relationships in an Infected Patient
- Host Relations
Host & Pathogen
- Pathogen provides virulence
- Host provides resistance
Host & Antibiotic
- Antibiotics provide toxicity
- Host provides pharmacokinetics
Relationships in an Infected Patient
- Antibiotic Relations
Antibiotic & Pathogen
- Pathogen provides resistance
- Antibiotic provides pharmacodynamic
Antibiotic & Host
- Host provides pharmacokinetics
- Antibiotic provides toxicity
Antibiotic & Commensals
- Commensals provide resistance
- Therapy provides pharmacodynamic
Relationships in an Infected Patient
- Pathogens Relations
Pathogen & Antibiotic
- Antibiotic provides pharmacodynamic
- Pathogen provides resistance
Pathogen & Host
- Host provides immune responses
- Pathogen provides infectious disease
Pathogen & Commensals
- Commensals provide colonization resistance
- Pathogen provides colonization
Relationships in an Infected Patient
- Commensal Relations
Commensal & Antibiotic
- Antibiotics provide pharmacodynamic
- Commensal provide resistance
Commensal & Pathogen
- Pathogen provide colonization resistance
- Commensal provide resistance
Factors in choosing antimicrobial therapy
- Part 1
- What disease is being treated
- Should the disease be treated with antibacterials
- What are the Suspected Organisms
- How Ill is the patient
- Are there Cultures To Direct antibacterial choice
- Is the patient Immunocompromised
- What are the current Susceptibility Patterns by site
- What are the Advantages/Disadvantage’s of available choices of susceptible antibacterial
- What are the Costs issues
Factors in choosing antimicrobial therapy
- Part 2
- What Route to use
- Limiting issues of Routes
- Evidence in choice of antibacterial in this particular case
- Evidence Based Guidelines (Are they up to date)
- Site and Severity of infection
- What dose to use (Does dose need to be adjusted)
- Any toxicities or allergies or special circumstances that would affect the drug
- Any way to prevent spread of infection
- How long should treatment be continued
- How should progress be monitored
When to use broad spectrum antibacterials
When the stakes are high broad agents should be used as being wrong in selecting an antibacterial can be dangerous
Site Specific Factors
Eye, Brain, and Prostate
- Are made up of non-fenestrated capillaries which impedes drug diffusion
Infections here are difficult to treat, may need to directly inject antibacterial to these sites
Biofilm
- Where can it form
- Water pipes
- Foreign substance inserted into the body (IV catheters, Artificial joints, Artificial heart valve)
- Tissues (Causes infections that are difficult to treat such as cystic fibrosis)
Biofilm
- Effects
Bacteria in biofilm becomes resistance and requires 10-1000 higher concentrations of antibacterials than free bacteria
- Usually we can not achieve these concentrations clinically
Biofilm
- Mechanism
Biofilm physically protects bacteria
- Though even when removed from the biofilm the bacteria remain resistant
When are antibacterial combinations required
- To broaden empiric coverage (When its hard to rule out a specific infection)
- Polymicrobial coverage
- To prevent emergence of resistance
- Synergy
Synergy
The combination of antibacterials is superior to the sum of both antibacterials given separately
- 1 + 1 > 2
Addition
The combination of antibacterials is superior but less than the sum of the effects of both antibacterials
- 1 + 1 > 1 to 2
Indifference
The combination of antibacterials is equal to either antibacterial given alone
- 1 + 1 = 1
Antagomism
The combination of antibacterials is inferior to either antibacterial given alone
- 1 + 1 < 1
Antibacterial Combinations
- Examples of Synergistic
Penicillin + Aminoglycosides
Piperacillin + Aminoglycosides (Combination antipseudomonal)
Sulfonamides + Trimethoprim
Beta-Lactam + Beta-Lactamase Inhibitor
Antibacterial Combinations
- Examples of Antagonism
Penicillin + Tetracycline
Gentamicin + Chloramphenicol
Antibacterial Combinations
- Disadvantages
- Antagonism
- Costs
- Adverse Effects
Antimicrobial Therapy
- Drug Interactions
Oral Anticoagulants
- Antibacterials can inhibit Vitamin K synthesis
Oral Contraceptives
- Antibacterials may interfere with Enterohepatic recycling of conjugates
Antimicrobial Therapy
- Oral Anticoagulants
Monitor after 3-5 days
Monitor INR carefully with Sulfonamides and reduce dose
Minitor INR carefully with Metronidazole
Antimicrobial Therapy
- Oral Contraceptives
Rifampin and Rifabutin can increase metabolism of ethinylestradiol
Antibacterials can cause diarrhea and/or vomiting that can decrease absorption of Oral Contraceptives
Antibacterials can reduce bacteria in GI tract and interfere with enterohepatic recycling (Reduces systemic estrogen)
Antimicrobial Therapy
- Additional Considerations
Allergic Reactions
Specific Toxicities
- Nephrotoxicity with aminoglycosides
Antibacterial Resistance
