Doripenem

Doripenem is a broad-spectrum carbapenem antibiotic with activity against many gram-positive and gram-negative aerobic bacteria, as well as a variety of anaerobes. Like other beta-lactam antibiotics, doripenem's bactericidal mechanism of action is mostly due to cell death after inhibition of bacterial enzymes called penicillin-bindng proteins (PBPs), which are responsible for peptidoglycan cross-linking during the synthesis of the bacterial cell wall. Carbapenems mainly have high affinity for PBPs 1a, 1b, 2 and 3. Inhibition of each PBP usually results in a different inactivating mechanism. Inhibition of PBPs 1a and 1b results in fast bacterial killing through the formation of spheroplasts, inhibition of PBP 2 results in rod-shaped bacteria to become spherical, and inhibition of PBP 3 results in filamentous-shaped organisms. The PBPs preferentially bound by different carbapenems depend on the organism. In E.coli and P.aeruginosa, doripenem binds to PBP 2, which is involved in the maintenance of cell shape, as well as to PBPs 3 and 4. Doripenem has a 1-beta-methyl side chain, which allows it to be relatively resistant to dehydropeptidase, as well as a trans-alpha-1-hydroxyethyl group at position 6 which provides beta-lactamase resistance. Like other carbapenems, doripenem is different from most beta-lactams due to its stability against hydrolysis by most beta-lactamases, including penicillinases, cephalosporinases, ESBL, and Amp-C producing enterobacteriaceae.