Study Notes

Beta-Lactam Antibiotics

Definition and Mechanism

Beta-lactam antibiotics are a class of antibacterial agents that inhibit cell wall synthesis in bacteria.
They work by binding to the enzyme DD-transpeptidase, which is necessary for cell wall formation.
This binding prevents the cross-linking of peptidoglycan chains, ultimately leading to cell lysis and death.

Types of Beta-Lactam Antibiotics

Penicillins:
- Natural penicillins (e.g. penicillin G, penicillin V)
- Semi-synthetic penicillins (e.g. ampicillin, amoxicillin)
- Beta-lactamase-resistant penicillins (e.g. methicillin, cloxacillin)
Cephalosporins:
- First-generation (e.g. cephalexin, cephalothin)
- Second-generation (e.g. cefaclor, cefuroxime)
- Third-generation (e.g. cefotaxime, ceftriaxone)
- Fourth-generation (e.g. cefepime, cefpirome)
Monobactams:
- Aztreonam
Carbapenems:
- Imipenem, meropenem, ertapenem

Spectrum of Activity

Beta-lactam antibiotics are effective against a wide range of Gram-positive and Gram-negative bacteria.
They are particularly effective against:
- Staphylococcus aureus
- Streptococcus pneumoniae
- Haemophilus influenzae
- Escherichia coli
However, they are not effective against:
- Anaerobic bacteria (e.g. Bacteroides fragilis)
- Mycobacteria (e.g. Mycobacterium tuberculosis)
- Fungi

Resistance and Side Effects

Resistance to beta-lactam antibiotics can occur due to:
- Production of beta-lactamase enzymes
- Alteration of the target enzyme DD-transpeptidase
- Changes in the bacterial cell wall
Common side effects of beta-lactam antibiotics include:
- Allergic reactions
- Gastrointestinal disturbances
- Diarrhea
- Clostridioides difficile infection

Description

This quiz covers the definition, mechanism, types, spectrum of activity, resistance, and side effects of beta-lactam antibiotics. It includes information on penicillins, cephalosporins, monobactams, and carbapenems.