Low-level resistance to the cephalosporin 3'-quinolone ester Ro 23-9424 in Escherichia coli

Antibiotic Hybrids: the Next Generation of Agents and Adjuvants against Gram-Negative Pathogens?

The global incidence of drug-resistant Gram-negative bacillary infections has been increasing, and there is a dire need to develop novel strategies to overcome this problem. Intrinsic resistance in Gram-negative bacteria, such as their protective outer membrane and constitutively overexpressed efflux pumps, is a major survival weapon that renders them refractory to current antibiotics. Several potential avenues to overcome this problem have been at the heart of antibiotic drug discovery in the past few decades. We review some of these strategies, with emphasis on antibiotic hybrids either as stand-alone antibacterial agents or as adjuvants that potentiate a primary antibiotic in Gram-negative bacteria. Antibiotic hybrid is defined in this review as a synthetic construct of two or more pharmacophores belonging to an established agent known to elicit a desired antimicrobial effect. The concepts, advances, and challenges of antibiotic hybrids are elaborated in this article. Moreover, we discuss several antibiotic hybrids that were or are in clinical evaluation. Mechanistic insights into how tobramycin-based antibiotic hybrids are able to potentiate legacy antibiotics in multidrug-resistant Gram-negative bacilli are also highlighted. Antibiotic hybrids indeed have a promising future as a therapeutic strategy to overcome drug resistance in Gram-negative pathogens and/or expand the usefulness of our current antibiotic arsenal.

Dual beta-lactam-fluoroquinolone compounds: a novel approach to antibacterial treatment

Codrugs comprise a beta-lactam-fluoroquinolone antibacterial hybrid. These new agents have been developed with the aim of enhancing the antibacterial spectrum of current therapies, overcoming intrinsic and acquired resistance, and diminishing severe side-effects. A few compounds, including Ro 23-9424, have entered Phase I clinical trials. Furthermore, a series of oral codrugs have been synthesised, although clear oral bioavailability has not yet been demonstrated. New drugs are urgently needed to treat Gram-positive resistant bacteria.