[Molecular mechanisms of bacterial resistance]

There is a great variety of resistance mechanisms observed in bacteria. Several mechanisms can operate simultaneously against a single antibiotic, and there are no species-specific mechanisms described so far. In many cases, resistance is mediated by mobile genetic elements (plasmids, phages and transposons), spreading among different bacterial genera, carrying in many instances multiresistant determinants. Administration of one type of antimicrobial agent can select resistance to other groups of antimicrobials. In summary, more details are found every day on these molecular processes. All this constitute an important tool for the design of new antimicrobials with broad specificity and higher efficacy in an attempt to control bacterial resistance. More important yet, this knowledge has a necessary implication which translates into a rational and adequate use of antimicrobial agents in the fight against bacterial infections.