Antimicrobial Therapy and Resistance

Antimicrobial Therapy and Resistance

• Selective Toxicity: Chemicals toxic to microbes, harmless to the host.
• Acquired Resistance: Microorganisms develop resistance to drugs over time. This often occurs due to overuse of antibiotics, particularly in agriculture.
• Suprainfection: Develops when broad-spectrum antibiotics eliminate normal flora organisms, not just the pathogens causing infection. Examples include C. diff, thrush, and vaginal infections.
• Antibiotic Resistance: Resistance is evolving rapidly in many prokaryotic species due to overuse of antibiotics, particularly in agriculture.
• Broad Spectrum Antibiotics: Effective against a wide variety of microbes.
• Narrow Spectrum Antibiotics: Effective against only a few microorganisms.
• C. difficile: Bacteria causing severe intestinal infections.
• Penicillins: Antibiotics ending in "-cillin," generally low toxicity.
• Beta-lactamases: Enzymes that inactivate penicillins. Methicillin-resistant Staphylococcus aureus (MRSA) is an example of a pathogen resistant to many antibiotics.
• MRSA: Methicillin-resistant Staphylococcus aureus; an infection caused by a pathogen resistant to many antibiotics.
• Ampicillin: A broad-spectrum penicillin used for various infections.

Additional Antimicrobial Classes

• Cephalosporins: Beta-lactam antibiotics similar to penicillins.
• Vancomycin: Glycopeptide antibiotic for severe infections. Skin irritation, a reaction called "red man syndrome," can occur with rapid IV infusions.
• Tetracyclines: Broad-spectrum antibiotics that inhibit protein synthesis.
• Macrolides: Broad-spectrum antibiotics that inhibit protein synthesis.
• Trimethoprim-Sulfamethoxazole: Combination antibiotic for urinary tract infections.
• Ciprofloxacin: Fluoroquinolone, often a first choice for anthrax.

Antimicrobial Treatment Strategies

• Peak and Trough: Monitoring serum drug levels for toxicity.
• Prophylactic Antibiotics: Prevent infection rather than treat established infections.
• Empiric Therapy: Antibiotic treatment given before identifying the organism.
• Penicillin Combinations: Combining penicillins with penicillinase-sensitive antibiotics to extend their antimicrobial spectrum. (e.g. Ampicillin/sulbactam, Amoxicillin/clavulanate, etc.)
• Broad Spectrum Penicillins: Ampicillin and amoxicillin are good examples.

Other Information

• Bacteriostatic: Stops the multiplication of bacteria
• Bactericidal: Kills bacteria directly.
• Allergy Assessment: Evaluate for penicillin allergy before administration.
• Drug Interactions: Check for interactions affecting antibiotic efficacy.
• Patient Monitoring: Observe clinical responses and lab results.
• Selection of Antibiotics: Criteria includes lab results (culture and sensitivity to identify the organism,drug sensitivity), allergies, and patient variables like liver/kidney function.

Specific Antibiotic Considerations

• Penicillin and Cephalosporin Cross-allergy: Important to know that a penicillin allergy often means an allergy to cephalosporins also.

• Potassium Penicillin G: Water-soluble solution for immediate onset; least toxic; monitor potassium levels.

• Glycopeptides: Structurally and functionally similar to penicillins; often treat severe infections.

• Cephalosporins: Similar to penicillin structures and wide uses, but can display different toxicities.

• 1st Generation Cephalosporins: Increased activity toward staphylococci; increased activity toward streptococci and gram-positive activity vs. 2nd/3rd generation.

• 2nd Generation Cephalosporins: Gram-positive cocci, Haemophilus influenzae, etc.

• 3rd Generation Cephalosporins: Effective against serious gram-negative infections.

• 4th Generation Cephalosporins: Gram-negative and gram-positive organisms, with activity against Pseudomonas.

• Drug Interactions: Cephalosporins may interfere with drugs that promote bleeding, and increase risk of nephrotoxicity when given with aminoglycosides, and increase risk of blood clots when given with anticoagulants. Alcohol can create a disulfiram-like reaction.

• Vancomycin Adverse Effects: Nephrotoxicity (kidney damage), ototoxicity (ear damage), red man syndrome.

• Tetracycline Adverse Effects: Gastrointestinal distress, interaction with other drugs, and blue man syndrome (discoloration of the skin).

• Aminoglycoside Adverse Effects: Nephrotoxicity (kidney damage), ototoxicity (ear damage), allergies, hypersensitivity reactions, neuromuscular blockade, and blood dyscrasias.

• Sulfonamide Adverse Effects: Hypersensitivity reactions (rash, Stevens-Johnson syndrome, and potentially fatal reactions), and interaction with other drugs.

• Trimethoprim: Drug used to prevent DNA bacterial synthesis in conjunction with sulfa drugs (trimethoprim-sulfamethoxazole).

• Fluoroquinolones adverse effects: Disrupt DNA replication; side effects include tendon rupture, especially the Achilles tendon.

• Ciprofloxacin Adverse Effects: Nausea, vomiting, diarrhea, abdominal pain, dizziness, headache, confusion, and visual disturbances.

• Drug and Food interactions of Cipro: Absorption reduced by aluminum or magnesium antacids, iron salts, zinc salts, sucralfate, and dairy/milk products.

Test your knowledge on antimicrobial therapy and the critical concepts of resistance in microorganisms. This quiz covers selective toxicity, suprainfection, and the roles of broad and narrow spectrum antibiotics. Delve into the complexities of antibiotic resistance and its implications for health.