Beta-Lactam Compounds and Antibiotics Quiz

Study Notes

Beta-Lactam Compounds

Monobactams, Carbapenems & Beta-Lactamase Inhibitors are all types of Beta-Lactam compounds.
Beta-Lactamase Inhibitors have weak antibacterial activity, and are often used in combination with other antibiotics to counteract resistance.
- Clavulanic acid is combined with Amoxicillin (co-amoxiclav) to enhance its effectiveness against Beta-Lactamase producing bacteria.
- Sulbactam is often used alongside Ampicillin.
- Tazobactam is often used in combination with Piperacillin.

Cell Wall & Membrane Active Agents

Vancomycin was previously a go-to treatment for MRSA (Methicillin Resistant Staphylococcus Aureus) infections.
- Red Neck/Man Syndrome is a common adverse effect, caused by histamine release and leading to skin flushing.
Bacitracin is another cell wall and membrane inhibitor.

Drugs that Inhibit Protein Synthesis

Tetracycline & Aminoglycosides primarily target the 30S ribosomal subunit.
Macrolides, Clindamycin & Chloramphenicol mainly target the 50S ribosomal subunit.

Tetracyclines

Effective against both gram-positive and gram-negative bacteria.
Absorption Issues:
- Impaired by food, Ca, Mg, Fe, Al, dairy products, antacids, and alkaline pH.
- Do not prescribe in patients taking medication or consuming food containing these elements to avoid impaired absorption.
Other Key Features:
- Crosses the placental barrier and is excreted in breast milk.
- Contraindicated in: pregnant women, lactating mothers, and children under 8 years old.
- Bony structure and tooth deposition can lead to deformities and growth inhibition.
- Common Side Effects:
  - Gastrointestinal disturbances due to coliform bacteria suppression.
  - Photosensitivity.
  - Vestibular reactions (affects the ears).

Macrolides

Thromycin, Erythromycin, Clarithromycin, and Azithromycin are common members of this class.
Erythromycin is often administered with an enteric coating to protect it from stomach acid.
Food impairs absorption of Erythromycin and can lead to GI disturbances.
Azithromycin has a long half-life allowing for once-daily dosing.

Clindamycin

Effective against anaerobic bacteria.
Frequently used in the treatment of periodontal diseases alongside metronidazole.
Pseudomembranous colitis (severe diarrhea) is a potential adverse effect due to Clostridium difficile overgrowth.

Chloramphenicol

Highly lipid-soluble, leading to reabsorption.
Metabolism occurs through conjugation.
Gray Baby Syndrome:
- Infants lack conjugation enzymes, leading to chloramphenicol accumulation.
- Symptoms include: vomiting, flaccidity, hypothermia, shock, collapse, and gray skin color.
Other Adverse Effects: CNS toxicity and bone marrow depression.
- Can suppress bone marrow function, leading to aplastic anemia (reversible after a week).

Aminoglycosides

Concentration-Dependent Killing: increasing the concentration of the drug leads to a more rapid and effective killing of bacteria.
Mostly used against gram-negative bacteria.
Irreversible Protein Synthesis Inhibitors: their adverse effects are also irreversible.
Ototoxicity and Nephrotoxicity are major adverse effect concerns - associated with all aminoglycosides.
Examples:
- Streptomycin (second-line drug for TB treatment).
- Tobramycin (commonly used for ophthalmic solutions).
- Neomycin, Tobramycin, and Gentamycin - the most nephrotoxic aminoglycosides.
Post-Antibiotic Effect: even after discontinuation of the drug, bactericidal activity can continue.

Drugs That Inhibited DNA Synthesis

Folate Synthesis Inhibition:
- Sulfonamides: interfere with folate synthesis, leading to a decrease in purine production (bacteriostatic).
- Co-trimoxazole: a combined treatment with trimethoprim and sulfamethoxazole.
DNA Gyrase Inhibition:
- Fluroquinolones: (bactericidal) inhibit DNA gyrase and cause DNA breaks, leading to cell death.
- Examples:
  - Floxacins: Ciprofloxacin, Ofloxacin.
  - Can bind to Ca, Al, Mg and Fe: affecting their effectiveness.
  - Arthropathy (cartilage damage): contraindicated in patients under 18 years old.

Treatment of Tuberculosis (TB)

Caused by Mycobacterium Tuberculosis, which is resistant to most antibiotics.
Mycobacterium tuberculosis grows slowly, making it difficult for antibiotics to effectively target it.
Mycobacteria have a lipid-rich cell wall that is difficult for antibiotics to penetrate.
Highly prone to developing antibiotic resistance.

First-Line TB Treatment (RIPES)

R: Rifampicin (inhibits RNA synthesis)
- Adverse Effect: red-orange discoloration of bodily fluids.
I: Isoniazid (highly active TB drug)
- Prodrug: needs to be converted into its active form within the body.
- Side-effects: can induce tuberculosis (major toxic effect), Peripheral neuropathy due to pyridoxine deficiency.
P: Pyrazinamide (prodrug)
- Active form is pyrazinoic acid.
- Hyperuricemia: high levels of uric acid in the blood.
E: Ethambutol
- Adverse Effect: retrobulbar neuritis (vision loss), red-green color blindness.

Second-Line TB Treatment

Streptomycin: ototoxicity and nephrotoxicity concerns are significant.

Description

Test your knowledge on Beta-Lactam compounds, their inhibitors, and cell wall active agents. This quiz covers key antibiotics like Vancomycin, Amoxicillin, and their mechanisms of action. Understand the combination therapies and their clinical implications in treating bacterial infections.