Genetic analyses of Streptococcus pneumoniae clinical isolates causing invasive pneumococcal disease (IPD) have revealed within the "susceptible population" a significant proportion of strains harboring a single, principally parC mutation within the quinolone-resistance determining region. The occurrence of first-step mutants predisposes S. pneumoniae to a subsequent and more rapid second-step mutation resulting in elevated levels of fluoroquinolone resistance and clinical failure.
Fluoroquinolones are a common therapeutic choice for residents of long-term care facilities and/or elderly patients in the community at higher risk of IPD. Despite the advent of the pneumococcal conjugate vaccine, levofloxacin resistance among vaccine serotypes is increasing, and the majority of these isolates are closely related to widespread antibiotic-resistant clones.
Use of fluoroquinolones with activity against levofloxacin-nonsusceptible isolates of S. pneumoniae should be considered in the management of IPD among elderly patients in the community and long-term care residents and among at-risk patients with chronic pulmonary infections.
*David Vaughan Consultants, Pickering, Ontario, Canada; †Replidyne Inc, Milford, CT and ‡Hubert Department of Global Health, Rollins School of Public Health and Division of Infectious Diseases, School of Medicine, Emory University, Atlanta, GA.
Dr Vaughan has received financial support from Oscient Pharmaceuticals.
Address correspondence and reprint requests to David J. Vaughan, PhD, David Vaughan Consultants, 456 Sheppard Avenue, Pickering ON Canada L1V 1E5. E-mail: email@example.com.