Aminoglycosides: An Overview

Aminiglycosides are bactericidal and active against some Gram-positive and many Gram-negative organisms. They are not absorbed from the gut (although there is a risk of absorption in inflammatory bowel disease and liver failure) and must therefore be given by injection for systemic infections.

Following active transport into the cell, they bind irreversibly to a specific aminoglycoside receptor on the bacterial 30S ribosomal subunit and interfere with the initiation complex between messenger RNA and the 30S subunit, thereby inhibiting initiation of protein synthesis, consequently leading to bacterial cell death. In addition, they induce misreading of the mRNA template causing incorrect amino acids to be incorporated into the growing polypeptide chain, consequently interfering with protein elongation.

Carbapenems: An Overview

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The carbapenems are a class of broad-spectrum beta-lactam antibacterials with activity against many gram-positive and gram-negative bacteria and anaerobes. They penetrate cell walls and bind to penicillin-binding protein (PBP) targets.

Imipenem has the greatest affinity for PBP 1A, 1B, and 2, and its lethal effect is related to binding to PBP 2 and 1B. This antibiotic is active against a wide range of gram-positive and gram-negative organisms and is stable in the presence of beta-lactamases.

Ertapenem has a particular affinity for PBPs 2 and 3. This agent is stable against hydrolysis by a variety of beta-lactamases, including penicillinases, cephalosporinases and extended-spectrum beta-lactamases.

The carbapenems are ineffective against MRSA or Enterococcus faecium.

They commonly cause mild transient aminotransferase elevations and can rarely result in clinically apparent, cholestatic liver injury.