Immunology - Antibiotics Flashcards
Mechanism of penicillin?
- Inhibit penicillin-binding proteins such as the enzyme DD-transpeptidase (this catalyses the cross-linking of peptidoglycans in bacterial cell walls)
- Inhibition of this process weakens the cell walls, allowing an influx of water into the cell
- This leads to cell swelling and then cell lysis.
What are 4 example Penicillin drugs?
- Penicillin V
- Amoxicillin/Co-Amoxiclav
- Flucloxacillin
- Tazocin
What is Penicillin V used to treat?
- Streptococcal infections e.g. tonsillitis, pneumonia, endocarditis and skin infections
- Clostridial infections e.g. tetanus
- Meningococcal infections e.g. meningitis
What is Amoxicillin/Co-Amoxiclav used to treat?
Gram-positive or Gram-negative pneumonia
E. coli UTI
Intra-abdominal sepsis
H. pylori eradication
What is Flucloxacillin used to treat?
Streptococcal infections including skin and soft tissue, osteomyelitis and septic arthritis
What is Tazocin used to treat?
Used for only very severe infections, especially where there is a broad spectrum of potential causative organisms, including Pseudomonas.
It is used to treat sepsis of almost all causes, in particular respiratory, urinary, skin, soft-tissue and intra-abdominal infections.
What are common side effects of penicillins?
GI upset, including antibiotic-associated C. difficile infection.
How common is a penicillin allergy?
A degree of allergy to penicillin is very common, affecting up to 10% of the population
Why are Cephalosporins and Carbapenems grouped together?
Due to their similar structural properties and mechanisms of action.
Mechanism of Cephalosporins and Carbapenems?
Like penicillins, these antibiotics get their antimicrobial effect from the presence of a ß-lactam ring in their structure; they inhibit the cross-linking of peptidoglycans in bacterial cell walls.
What are 3 examples of Cephalosporins?
- Cefotaxime
- Cetriaxone
- Cefuroxime.
What is major example of Carbapenems?
Meropenem
What are Cephalosporins and Carbapenems used to treat?
Broad-spectrum, but as they have evolved, cephalosporins have become more suited for use against Gram-negative bacteria.
As both these types of antibiotic have a high chance of leading to bacterial resistance, they are usually reserved for very serious infections.
Common side effects of Cephalosporins and Carbapenems?
Simple GI upset
Antibiotic-associated colitis
Hypersensitivity reactions.
Why must extra care be taken giving Cephalosporins and Carbapenems in penicillin-allergic patients?
As their structure and mechanism is similar to penicillin, there may be cross-reactivity in penicillin-allergic patients, thus extreme caution must be taken.
Cautions/contraindications of Cephalosporins and Carbapenems?
Use with extreme caution in those with penicillin allergy
Use with caution in those at high risk of C. difficile
Use with caution in renal impairment
Mechanism of glycopeptides?
Glycopeptides prevent the formation of cross links in the peptidoglycan cell wall.
How do glycopeptides differ from penicillins?
While penicillins irreversibly and competitively inhibit DD-transpeptidase, glycopeptides bind to the proteins in the cell wall themselves to prevent DD-transpeptidase from binding.
2 examples of glycopeptides?
- Vancomycin
2. Teicoplanin
What is Vanomycin used for?
- Orally for severe C. difficile infections
- Intravenously for severe soft tissue/bone/joint infections as gram-positive cover.
What is Teicoplanin used for?
- IV for gram-positive cover, either as treatment
- Commonly used as surgical prophylaxis in penicillin allergic patients.