Micro CH 10 Flashcards
Penicillin Resistance
Bacteria develops penicillin resistance by producing an enzyme called beta-lactamase that breaks down the penicilin molecule, making if ineffective
Penicillin Mechanism of Action
Penicillin targets the bacterial cell wall and prevents its formation
Cephalosporin Mechanism of Actiion
Also inhibit cell wall synthesis, disrupts the peptidoglycan layer
Macrolide Mechanisms of Action
Inhibit bacterial protein synthesis by binding to the ribosome and preventing the elongation of the protein chain
Amino-glycoside Mechanisms of Action
Bind to the ribosome and cause errors in the protein synthesis process
Kirby-Bauer Test
The Kirby-Bauer test (disk diffusion method) is used to test the effectiveness of antibiotics on bacteria.
Antibiotic-impregnated disks are placed on a bacterial culture, and the zone of inhibition (area where bacteria cannot grow) is measured to determine antibiotic effectiveness.
Zone of Inhibition
The zone of inhibition is the clear area around an antibiotic disk where bacteria cannot grow.
A larger zone indicates the antibiotic is more effective.
Emerging Drug Resistance (Basis and Contributors)
Emerging drug resistance happens when bacteria evolve to become resistant to antibiotics.
Contributors:
Overuse and misuse of antibiotics (e.g., taking antibiotics for viral infections).
Antibiotic use in agriculture.
Incomplete courses of antibiotics.
Horizontal gene transfer (bacteria sharing resistance genes).
Narrow-Spectrum Antibiotics (Definition & Examples; Consequences)
Narrow-spectrum antibiotics are effective against specific types of bacteria.
Examples: Penicillin, vancomycin.
Consequences:
Advantages: Less disruption to normal flora (good bacteria).
Disadvantages: It may not work against a wide variety of infections.
Ribosomal Targeting
Broad-Spectrum Antibiotics (Definition & Examples; Consequences)
Definition: Broad-spectrum antibiotics affect a wide range of bacteria, both gram-positive and gram-negative.
Examples:
Tetracycline
Amoxicillin
Chloramphenicol
Consequences:
Advantages: Useful when the specific bacteria causing an infection is unknown.
Disadvantages: It can harm normal flora (good bacteria), leading to side effects like yeast infections or antibiotic resistance.
Therapeutic Index
Definition: The therapeutic index is the ratio between the toxic dose and the therapeutic dose of a drug.
A higher therapeutic index = a safer drug (less toxic to the body).
Lower therapeutic index = more risk of toxicity.
Drugs with High Selective Toxicity
Selective toxicity means the drug is more toxic to microorganisms than to human cells.
Drugs with high selective toxicity:
Penicillin targets bacterial cell walls, but humans don’t have cell walls.
Aminoglycosides (target bacterial ribosomes, which are different from human ribosomes).
Common Antimicrobial Drug Side Effects
Gastrointestinal issues: Nausea, vomiting, and diarrhea.
Allergic reactions: Skin rashes, itching.
Yeast infections: Antibiotics can disrupt normal flora, leading to overgrowth of yeast (e.g., Candida).
Serious Antimicrobial Drug Side Effects
Kidney damage: Some antibiotics (e.g., aminoglycosides) can harm the kidneys.
Liver damage: Drugs like rifampin can affect liver function.
Hearing loss: Aminoglycosides (e.g., gentamicin) can lead to ototoxicity (hearing damage).
Bone marrow suppression: Some drugs like chloramphenicol can interfere with blood cell production.
Prophylaxis
Definition: The use of antimicrobial drugs to prevent infections before they happen (e.g., before surgery).
Examples:
Antibiotics for surgery to prevent post-surgical infections.
HIV patients may take antiretroviral drugs to prevent infection.
