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Questions and Answers
Questions and Answers
What is a mechanism associated with microbial resistance to antibiotics?
What is a mechanism associated with microbial resistance to antibiotics?
- Increase in microbial membrane permeability to antibiotics
- Development of new antibiotics
- Production of antibiotic inactivating enzymes (correct)
- Use of adjunctive agents to protect against antibiotic inactivation
What is a key strategy to combat microbial resistance?
What is a key strategy to combat microbial resistance?
- Increased use of single antibiotic regimens
- Use of antibiotic combinations
- Decreased development of new antibiotics
- Avoidance of misuse of antibiotics (correct)
What is the main factor to consider when selecting an antimicrobial agent?
What is the main factor to consider when selecting an antimicrobial agent?
- Safety/Toxicity
- Efficacy/Spectrum (correct)
- Convenience/Compliance
- Cost
What characteristic should the ideal antimicrobial agent have?
What characteristic should the ideal antimicrobial agent have?
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What is the main reason for not using antibacterial agents to treat viral diseases?
What is the main reason for not using antibacterial agents to treat viral diseases?
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What is the main concern related to the use of antibiotics for non-bacterial conditions?
What is the main concern related to the use of antibiotics for non-bacterial conditions?
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What is the main reason for not finishing the treatment duration of antibiotics?
What is the main reason for not finishing the treatment duration of antibiotics?
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Questions and Answers
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Study Notes
Study Notes
Key Concepts in Antimicrobial Therapy
- Antibiotics: Substances that kill or inhibit the growth of microorganisms.
- Selective Toxicity: Targeting microorganisms without harming human cells, exploiting differences in metabolism and structure.
- Therapeutic Index: Ratio indicating the safety of a drug; the higher the index, the safer the drug.
- Bacteriostatic vs. Bactericidal: Bactericidal drugs kill bacteria, whereas bacteriostatic drugs inhibit growth.
Mechanisms of Action
- Antibiotics can:
- Inhibit cell wall synthesis (common in betalactams).
- Interfere with cell membrane function.
- Disrupt ribosomal function (protein synthesis), either reversibly (bacteriostatic) or irreversibly (bactericidal).
- Inhibit nucleic acid metabolism and block enzymatic activities (antimetabolites).
Microbial Classification
- Important microorganisms include:
- Bacteria: e.g., Staphylococcus aureus.
- Viruses: e.g., HIV.
- Fungi: e.g., Candida albicans.
- Parasites: e.g., Plasmodium falciparum.
Types of Antimicrobial Therapy
- Prophylaxis: Prevents infection in high-risk patients (e.g., immunosuppressed individuals).
- Pre-emptive Therapy: For asymptomatic patients showing laboratory signs of infection; delivered prior to symptom development.
- Empiric Therapy: Started before specific organisms are identified, based on common pathogens.
- Definitive Therapy: Narrowed down once pathogen identification and susceptibility are available.
- Suppressive Therapy: Continued at lower doses to manage chronic infections without complete eradication.
Pharmacokinetic Principles
- Minimum Inhibitory Concentration (MIC): Lowest concentration of an antibiotic that prevents visible growth of bacteria.
- Minimum Bactericidal Concentration (MBC): Concentration required to kill the bacteria.
- Inoculum Effect: Increased bacterial density requires higher levels of antibiotics to achieve efficacy.
Bactericidal vs. Bacteriostatic Activities
- Bactericidal Drugs: Useful in life-threatening infections; effective when host defenses are impaired.
- Bacteriostatic Drugs: Require active host immune responses for efficacy and do not kill bacteria directly.
- Post-Antibiotic Effect (PAE): Continued suppression of bacterial growth after removal of antibiotic.
Dosing Considerations
- Continuous dosing maintains stable drug levels, while bolus dosing produces high peaks but may risk toxicity.
- Time-Dependent Killing: Drug effects depend on maintaining concentrations above MIC for extended periods (e.g., beta-lactams).
- Concentration-Dependent Killing: Increased effectiveness with higher peak concentrations (e.g., aminoglycosides).
Phases of Bacterial Growth
- Lag Phase: Initial metabolic activity without cell division.
- Log Phase: Rapid division; effective for beta-lactam drugs.
- Stationary Phase: Cell division slows; balance of new cells and deaths.
- Death Phase: Declining viable bacteria count.
Antimicrobial Drug Combinations
- Most infections should ideally be treated with single agents; combination therapy may lead to synergism or antagonism.
- Synergism: Combined effects are greater than individual effects; important in specific pathogen cases.
- Antagonism: Combined effects are less effective; notable with bacteriostatic agents inhibiting the efficacy of bactericidal antibiotics.
Clinical Decision-Making
- Selecting appropriate antibiotics involves understanding if a drug is cidal or static and using guidelines for effective treatment.
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