Biol 20: Chapter 14
Continuation of Chapter 30: Control of Microorganisms and Antibiotics
Introduction to Antibiotics
Antibiotics are derived from two main types of chemicals:
Natural Chemicals: Produced and extracted from live organisms.
Artificial Chemicals: Man-made or synthetic chemicals.
Historical Background of Antibiotics
Edward Fleming's discovery of penicillin in 1928 is pivotal:
It was considered a wonder drug during the 1940s.
Helped save many lives, particularly during World War II, allowing wounded soldiers to recover from infections.
Recent challenges with antibiotics include the rise of superbugs due to overuse.
Definitions and Key Terminology
Antibiotic: Chemicals/substances from living organisms that can kill microbes.
Antimicrobial Drugs: Include both natural and artificial compounds targeting micro-organisms.
Selective Toxicity: The ability of drugs to selectively target pathogens without damaging host cells. Some antimicrobials lack this feature, leading to side effects.
Important Figures in Antibiotic Discovery
Alexander Fleming: Discovered penicillin using staphylococcus aureus in 1928 after a contamination incident where he noted that mold disrupted bacterial growth.
Howard Florey and Ernst Boris Chain: Conducted the first human trials of penicillin, leading to public release.
Selman Waksman: Studied soil microorganisms, discovering actinobacteria which produce numerous antibiotics.
Paul Ehrlich: Developed "Magic Bullet," an arsenic compound (Compound 606) used to treat syphilis and gonorrhea, marking the beginning of chemotherapy.
Antibiotic Types and Usage
Bactericidal: Antibiotics that kill bacteria.
Bacteriostatic: Antibiotics that inhibit bacterial growth; may not be sufficient for severe infections.
Broad Spectrum Antibiotics: Effective against a wide range of bacteria (both Gram-positive and Gram-negative). Used when pathogens are unidentified or for mixed infections.
Narrow Spectrum Antibiotics: Target specific types of bacteria. Effective when the pathogen is known, reducing the risk of superinfections.
Risks of Antibiotic Usage
Overuse can lead to superinfections where resistant bacteria flourish due to the loss of normal microbiota.
It is important to complete antibiotic courses to eliminate all pathogenic bacteria and reduce the development of resistance.
Administration Routes of Antibiotics
Oral: Convenient but slower absorption; not ideal for critically ill patients.
Intravenous (IV): Rapid and effective for severe illnesses.
Intramuscular (IM): Also effective but slightly slower than IV.
Topical: Used for superficial skin infections.
Clinical Considerations
Physicians must choose the appropriate antibiotic type based on infection type, patient health, and infection severity.
Regular assessments and adjustments to treatment plans are key to effective resolution of infections.
Awareness of potential side effects and the importance of maintaining gut flora during antibiotic treatment is crucial.
video 2
Chapter 14: Antimicrobial Drugs
Introduction to Antibiotics
Discussion of historical figures: Paul Elbrick, Lori and Shane, Salman Watsman.
Compound 606 introduced for syphilis; noted as the first antimicrobial agent.
Definition of terms related to antibiotic action and spectrum:
Bactericidal: kills bacteria.
Bacteriostatic: inhibits the growth of bacteria.
Broad Spectrum: effective against a wide range of bacteria (both Gram-positive and Gram-negative).
Narrow Spectrum: effective against specific types of bacteria.
Effects of Long-Term Use of Broad Spectrum Antibiotics:
Can lead to superinfections and resistance development.
Importance of understanding patient medication history to avoid adverse interactions (e.g., antacids affecting antibiotic absorption).
Route of Administration:
Oral: most convenient but may undergo degradation in the GI tract.
Intravenous (IV): delivers the drug directly into the bloodstream, faster effects.
Intramuscular (IM): involves invasive methods (parental route).
Drug Interactions:
Synergism: combination of drugs produces a greater effect (e.g., combination therapy for HIV).
Antagonism: drugs may counteract each other; importance of disclosing all medications to the healthcare provider.
Example: taking antacids can interfere with antibiotic efficacy by altering gastric pH.
Example of pH Impact on Drug Absorption:
Regular antacid use can elevate stomach pH and negatively impact digestion and absorption of medications.
The Role of the Liver:
The liver is a crucial organ for processing all substances entering the bloodstream, acting as a filtering system before circulation.
Important Bacterial Genera:
Staphylococcus aureus (Fleming’s observation).
Streptococcus pyogenes (narrow-spectrum antibiotic treatment).
Antimicrobial Drug Classifications:
Focus on various antibiotics targeting different cellular mechanisms:
Cell Wall Inhibitors:
Beta-lactam antibiotics (e.g., penicillins, cephalosporins).
Example: Methicillin for staph; resistance development to penicillin.
Protein Synthesis Inhibitors:
Target ribosomal subunits; aminoglycosides (30S) and macrolides (50S).
Chloramphenicol has associated risks (aplastic anemia in newborns).
Metabolic Pathway Inhibitors:
Sulfonamides, trimethoprim - impact on folic acid synthesis.
Nucleic Acid Synthesis Inhibitors:
Fluoroquinolones (e.g., ciprofloxacin) targeting DNA gyrase.
Rifampin used to treat tuberculosis (TB) along with isoniazid (mycolic acid synthesis inhibitor).
Viral and Fungal Infections:
Antifungal strategies target chitin and ergosterol, unique to fungal cells.
Antiviral drugs exist but are limited due to viral mutation rates; key drugs include acyclovir for herpes.
Antibiotic Resistance:
Resistance mechanisms: blocking entry, inactivating enzymes, altering targets, and efflux pumps.
Understanding escape pathogens (e.g., Enterococcus faecium, Staphylococcus aureus) as significant clinical challenges.
Recap of Key Points and Questions:
Importance of antibiotic stewardship to prevent resistance development.
Prepare for next topics (Chapters 8 and 10).