[Quinolones and Streptococcus pneumoniae. Mechanisms of action and resistance].

Streptococcus pneumoniae is considered the most frequent bacterial cause of community-acquired pneumonia, and is involved in a significant number of cases of acute exacerbations of chronic bronchitis, acute otitis, sinusitis, meningitis and other infectious diseases. Fluoroquinolones have been extensively investigated in recent years in the search for new agents that has been prompted by the emergence of resistance in this microorganism. Furthermore, the study of resistance from a molecular biology standpoint has helped in elucidating almost all the biochemical mechanisms of resistance and the routes of dissemination of genetic information between bacteria. This short review is focused on the mechanism of action of quinolones and on the mechanisms responsible for resistance of S. pneumoniae to them, given their clinical and epidemiological relevance. S. pneumoniae is a case apart because bactericidal activity against this microorganism can be produced through gyrase, topoisomerase IV or both, depending on the quinolone structure, which shows that structure has an influence on the success of treatment. Knowledge of the resistance prototype is therefore important so that the appropriate antibiotic therapy can be recommended when indicated.