Β-Lactam antibiotic

Class of broad-spectrum antibiotics

β-Lactam antibiotics are a class of broad-spectrum antibiotics that contain a β-lactam ring in their molecular structures. This class includes penicillins, cephalosporins, carbapenems, and monobactams, which are among the most widely used antibiotics in the world.

Structure and Mechanism of Action

Beta-lactam ring closure routes

The β-lactam ring is a four-membered lactam, which is a cyclic amide. The integrity of this ring is crucial for the antibiotic activity of these compounds. β-Lactam antibiotics work by inhibiting the synthesis of the bacterial cell wall, specifically by targeting the penicillin-binding proteins (PBPs) that are essential for cell wall construction.

Penicillin inhibition of cell wall synthesis

The inhibition of PBPs prevents the cross-linking of peptidoglycan chains, which is a critical step in cell wall biosynthesis. This leads to the weakening of the cell wall and eventually causes cell lysis and death, particularly in actively dividing bacteria.

Types of β-Lactam Antibiotics

Penicillins

Penicillins were the first β-lactam antibiotics discovered and are still widely used today. They are effective against a variety of Gram-positive and some Gram-negative bacteria. Common penicillins include penicillin G, penicillin V, amoxicillin, and ampicillin.

Amoxicillin structure

Amoxicillin is a widely used penicillin that is often combined with clavulanic acid to overcome resistance.

Cephalosporins

Cephalosporins are similar to penicillins but have a broader spectrum of activity. They are classified into generations, with each subsequent generation having increased activity against Gram-negative bacteria and better resistance to β-lactamases.

Carbapenems

Carbapenems are highly resistant to most β-lactamases and have a very broad spectrum of activity. They are often used as a last resort for treating severe infections caused by multidrug-resistant bacteria.

Monobactams

Monobactams, such as aztreonam, are effective primarily against Gram-negative bacteria and are resistant to some β-lactamases.

Resistance

Resistance to β-lactam antibiotics is a significant clinical problem. The most common mechanism of resistance is the production of β-lactamases, enzymes that hydrolyze the β-lactam ring, rendering the antibiotic ineffective.

Clavulanic acid structure

Clavulanic acid is a β-lactamase inhibitor that is often combined with β-lactam antibiotics to overcome resistance.

Clinical Use

β-Lactam antibiotics are used to treat a wide range of infections, including pneumonia, meningitis, sepsis, and urinary tract infections. They are generally well-tolerated, but allergic reactions can occur in some individuals.

Related Pages

• Antibiotic resistance
• Penicillin
• Cephalosporin
• Carbapenem
• Monobactam