Potential of old-generation antibiotics to address current need for new antibiotics.

Despite the constantly increasing need for new antimicrobial agents, antibiotic drug discovery and development seem to have greatly decelerated in recent years. Presented with the significant problem of advancing antimicrobial resistance, the global scientific community has attempted to find alternative solutions; one of the most promising ones is the evaluation and use of old antibiotic compounds. Due to the low-level use of many of the old antibiotic compounds, these have remained active against a large number of currently prevalent bacterial isolates. Thus, clinicians are beginning to re-evaluate their use in various patient populations and infections, despite the fact that they were previously thought to be less effective and/or more toxic than newer agents. A number of old antibiotic compounds, such as polymyxins, fosfomycin, fusidic acid, cotrimoxazole, aminoglycosides and chloramphenicol, are re-emerging as valuable alternatives for the treatment of difficult-to-treat infections. The availability of novel genetic and molecular modification methods provides hope that the toxicity and efficacy drawbacks presented by some of these agents can be surpassed in the future.