Carbapenem Antibiotics

Carbapenems are bactericidal beta-lactam antibiotics used mainly for severe infections caused by susceptible bacteria. They possess a distinctive carbapenem nucleus and combine unusually broad antibacterial activity with resistance to hydrolysis by many beta-lactamases.

Distinctive chemical structure and action

Their beta-lactam ring is fused to an unsaturated five-membered ring in which carbon replaces the sulfur found in penicillins. Like other beta-lactams, they bind penicillin-binding proteins, inhibit peptidoglycan cross-linking and thereby disrupt bacterial cell-wall synthesis.

Spectrum and beta-lactamase stability

• Carbapenems act against many Gram-positive, Gram-negative and anaerobic bacteria, giving them one of the broadest spectra among beta-lactams.
• They resist many clinically important beta-lactamases, including numerous extended-spectrum beta-lactamases and AmpC enzymes.
• They do not reliably cover every pathogen: atypical bacteria lack the relevant cell-wall target, while methicillin-resistant staphylococci are generally resistant.
• Individual agents differ: ertapenem lacks reliable activity against Pseudomonas aeruginosa and Acinetobacter species.

Clinical use and limitations

Carbapenems are generally administered parenterally and are reserved for serious infections where narrower agents are unsuitable. Imipenem is combined with cilastatin, which prevents its breakdown by renal dehydropeptidase.

• Carbapenemases can hydrolyse these drugs, producing carbapenem resistance that may leave few effective treatment options.
• Their broad ecological impact and resistance risk make culture-guided use and antimicrobial stewardship especially important.