Quinolone resistance: Older concepts and newer developments

New quinolone compounds have been recommended for use in the treatment of respiratory tract infections, particularly pneumonia caused by multi drug-resistant Streptococcus pneumoniae. Of concern, however, is the recent emergence of pneumococcal isolates with reduced susceptibilities to both old and new quinolone compounds. This necessitates the employment of quinolone-use strategies aimed at restricting the emergence of resistance, to extend the effectiveness of this very important class of antibacterial agents. This article provides a comprehensive review of the recent discoveries in type II topoisomerase/ quinolone structure-function relationships. It also addresses new insights into the mechanisms of quinolone resistance, the predicted trends in quinolone resistance, and possible strategies for quinolone use against S. pneumoniae.