Blood Culture and Susceptibility Results and Allergy History Do Not Influence Fluoroquinolone Use in the Treatment of Community-Acquired Pneumonia Nancy N. Chang, Pharm.D., Cynthia K. Murray, Ph.D., Peter M. Houck, M.D., Dale W. Bratzler, D.O., M.P.H., Claudette Greenway, R.N., and B. Joseph Guglielmo, Pharm.D. Study Objective. To determine the influence of blood culture and susceptibility results and antimicrobial allergy history on fluoroquinolone use in the treatment of community-acquired pneumonia. Design. Retrospective analysis of medical records. Setting. Centers for Medicare and Medicaid Services, Seattle, Washington. Patients. A total of 10,275 Medicare beneficiaries hospitalized with the diagnosis of pneumonia received antimicrobial treatment within 24 hours of admission. Of these patients, 288 had blood cultures positive for pneumococcus and were matched one-to-one with patients with negative blood and sputum cultures. Measurements and Main Results. Antimicrobial use at the beginning and end of hospitalization, culture and susceptibility results, and patient allergies were recorded retrospectively and compared between two matched groups: patients with blood cultures positive for Streptococcus pneumoniae and those whose blood and sputum cultures were negative. Neither culture and susceptibility results nor allergy history affected the rate of fluoro- quinolone use. Despite infection due to penicillin-susceptible pneumococci and no penicillin allergy, patients received therapy with fluoroquinolones (26.7%) as frequently as those with culture-negative pneumonia (34.9%; p=0.401). Conclusion. Fluoroquinolones are prescribed despite microbiologic confirmation of penicillin-susceptible pneumococcal pneumonia in the absence of penicillin allergy. These prescribing patterns may contribute to selection pressure associated with fluoroquinolone-resistant gram-positive and gram-negative bacteria. Key Words: fluoroquinolone, community-acquired pneumonia, fluoro- quinolone-resistant bacteria, gram-positive bacteria, gram-negative bacteria, allergy history, culture results. (Pharmacotherapy 2005;25(1):59–66) Guidelines have been developed regarding management of hospitalized patients with community-acquired pneumonia (CAP). 1–4 The Canadian Infectious Diseases Society, the Canadian Thoracic Society, the Infectious Diseases Society of America (IDSA), and the American Thoracic Society to varying degrees recommend empiric fluoroquinolones because of their activity against drug-resistant Streptococcus pneumoniae, -lactamase–producing Haemophilus influenzae, and atypical pathogens. 1–3 In contrast, the Drug-Resistant Streptococcus pneumoniae Working Group advocates against empiric use of fluoroquinolones because of their broad- spectrum activity against important community- acquired and nosocomial gram-negative organisms