Risk factors and clinical significance of invasive infections caused by levofloxacin-resistant Streptococcus pneumoniae

PURPOSE: Fluoroquinolones are recommended for the treatment of pneumonia. The recognition of risk factors for invasive levofloxacin-resistant Streptococcus pneumoniae is important for the design of treatment. METHODS: A retrospective review of cases of invasive pneumococcal infections in adults was undertaken. Epidemiologic data, predisposing factors, clinical variables, and outcome were recorded from previously established protocols. Antimicrobial susceptibility was determined by disk diffusion and the Etest method. Serotyping was performed by latex agglutination and Quellung reaction. RESULTS: Twenty patients with infection caused by levofloxacin-resistant pneumococci [minimum inhibitory concentration (MIC) ≥2 μg/ml] were compared with 102 patients harboring levofloxacin-susceptible strains; 80 % of levofloxacin-resistant pneumococci were resistant to ≥3 antibiotics but susceptible to penicillin. Most levofloxacin-resistant strains (80 %) belonged to serotype 8. In comparison, only 8 % of levofloxacin-susceptible pneumococci belonged to serotype 8. In the multivariate analysis, residence in public shelters [odds ratio (OR) 26.13; p 0.002], previous hospitalization (OR 61.77; p < 0.001), human immunodeficiency virus (HIV) infection (OR 28.14; p = 0.009), and heavy smoking (OR 14.41; p = 0.016) were associated with an increased risk of infection by levofloxacin-resistant pneumococci. Mortality caused by levofloxacin-resistant and levofloxacin-susceptible pneumococci was 35 and 14 %, respectively. Among HIV-positive individuals infected with levofloxacin-resistant pneumococci 44 % died, but only 12.5 % of HIV-positive patients with levofloxacin-susceptible strains died. CONCLUSIONS: We observed the emergence of serotype 8 as the main cause of invasive disease caused by levofloxacin-resistant S. pneumoniae. HIV-positive patients seem to be prone to infection caused by multidrug-resistant serotype 8 and have a high mortality rate.