A Nosocomial Outbreak of Fluoroquinolone‐ResistantStreptococcus pneumoniae

Abstract

Over the course of a 20-month period, in a hospital respiratory ward in which ciprofloxacin was often used as empirical antimicrobial therapy for lower respiratory tract infections (LRTIs), 16 patients with chronic bronchitis developed nosocomial LRTIs caused by penicillin- and ciprofloxacin-resistant Streptococcus pneumoniae (serotype 23 F). The minimum inhibitory concentration (MIC) of ciprofloxacin for all isolates from the first 9 patients was 4 microg/mL, in association with a parC mutation. Isolates from the subsequent 7 patients all had a ciprofloxacin MIC of 16 microg/mL, in association with an additional mutation in gyrA. The MICs for this isolate were 8 microg/mL of levofloxacin (resistant), 2 microg/mL of moxifloxacin and gatifloxacin (intermediately resistant), and 0.12 microg/mL of gemifloxacin. This outbreak demonstrates the ability of S. pneumoniae to acquire multiple mutations that result in increasing levels of resistance to the fluoroquinolones and to be transmitted from person to person.

Bacterial Spectrum and Pattern of Antimicrobial Sensitivity Among Outpatients With Pneumonia in a Tertiary Care Hospital

“…Shefet et al in a Cochrane metaanalysis of 24 trials including 5015 randomized patients found no benefit of atypical cover (Fluoroquinolone monotherapy versus nonatypical monotherapy). Liu et al in a prospective study of 610 patients found that susceptibility of Streptococcus pneumoniae to Penicillin and azithromycin was 77.8% and 20.6% respectively, while we found sensitivity rate to penicillin and azithromycin as 18.7% and 56.2% respectively which was opposite to the findings of Liu et al [10,11,12,13] …”

Efficacy and safety of levofloxacin in the context of other contemporary fluoroquinolones: a review

“…18 Some evidence shows that bacterial resistance may lead to treatment failure. 19 Such uncommon reports of treatment failure with levofloxacin have occurred mostly among predisposed hospitalized patients with chronic respiratory disease. 20 In most countries, levofloxacin resistance among S pneumoniae is Ͻ1%; the minimum inhibitory concentration for 90% of isolates (MIC 90 ) remains at 1 mg/L 17 ; and, provided that optimized regimens are used, fluoroquinolones, including levofloxacin, remain highly effective against this pathogen.…”

Relative Fitness of Fluoroquinolone-resistantStreptococcus pneumoniae

“…The emergence of quinolone-resistant S. pneumoniae (QRSP) appears to be more dependent on fluoroquinolone selection of de novo spontaneous point mutations in the quinolone resistance-determining regions (QRDRs) of the topoisomerase genes gyrA and parC than on clonal dissemination (9-13). However, some studies reported occurrences of clonal relatedness among QRSP (11,(14)(15)(16).To investigate the relative fitness of QRSP, we conducted a competition study of a fluoroquinolone-susceptible clinical strain of S. pneumoniae (EF3030) with 2 of its fluoroquinolone-resistant isogenic mutants that had 2 common QRDR point mutation combinations. These 3 strains were analyzed by using an in vitro growth model, an in vivo nasopharyngeal colonization model, and an in vivo pneumonia model.…”

“…The emergence of quinolone-resistant S. pneumoniae (QRSP) appears to be more dependent on fluoroquinolone selection of de novo spontaneous point mutations in the quinolone resistance-determining regions (QRDRs) of the topoisomerase genes gyrA and parC than on clonal dissemination (9)(10)(11)(12)(13). However, some studies reported occurrences of clonal relatedness among QRSP (11,(14)(15)(16).…”