title: Fluoroquinolone-nonsusceptible Streptococcus pneumoniae isolates from a medical center in the pneumococcal conjugate vaccine era.
abstract: OBJECTIVE
  Streptococcus pneumoniae is one of the most common pathogens to cause mucosal and invasive infection in humans. Resistance to fluoroquinolones (FQ) is associated with clinical failure when treating pneumococcal diseases and increase of mortality.
  
  
  METHODS
  We collected clinical isolates of S. pneumoniae from January 2011 to July 2015 at Chang Gung Memorial Hospital, Taoyuan, Taiwan. Susceptibility to FQ was examined by disk diffusion method. Levofloxacin or moxifloxacin-nonsusceptible S. pneumoniae isolates were analyzed by serotyping, multilocus sequence typing, and sequencing of the quinolone resistance-determining regions (QRDRs) of gyrA, gyrB, parC, and parE.
  
  
  RESULTS
  During the study period, 42 FQ-nonsusceptible pneumococcal isolates were identified. The rate increased from 1.6% of total pneumococcal isolates (2 of 127) in 2011 to 4.6% (13 of 283) in 2014, then decreased to 1.5% (3 of 202) in the first half of 2015. These isolates belonged to 13 serotypes, and serotype 14 (12 of 42, 33.3%) was the most prevalent. Most of the isolates belonged to international clones or their variants. After QRDR analysis, there were 19 isolates in five clusters that shared both the same sequence type and QRDR mutation.
  
  
  CONCLUSIONS
  FQ resistance initially emerged in either vaccine or nonvaccine serotypes. The majority of isolates were international clones or related variants, suggesting that resistance was disseminated through clonal spread. The wide use of pneumococcal conjugate vaccine since 2013 appears to have reduced the spread of FQ-nonsusceptible pneumococci.
authors.affiliation: Division of Pediatric Infectious Diseases, Department of Pediatrics, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Taoyuan, Taiwan.
authors.forename: Hsin-Hang
authors.initials: HH
authors.lastname: Chen
authors.affiliation: Department of Laboratory Medicine, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Taoyuan, Taiwan.
authors.forename: Hsin-Chieh
authors.initials: HC
authors.lastname: Li
authors.affiliation: Department of Laboratory Medicine, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Taoyuan, Taiwan; Molecular Infectious Disease Research Center, Chang Gung Memorial Hospital, Taoyuan, Taiwan. Electronic address: sulinhui@gmail.com.
authors.forename: Lin-Hui
authors.initials: LH
authors.lastname: Su
authors.affiliation: Division of Pediatric Infectious Diseases, Department of Pediatrics, Chang Gung Memorial Hospital, Chang Gung University College of Medicine, Taoyuan, Taiwan; Molecular Infectious Disease Research Center, Chang Gung Memorial Hospital, Taoyuan, Taiwan. Electronic address: chchiu@cgmh.org.tw.
authors.forename: Cheng-Hsun
authors.initials: CH
authors.lastname: Chiu
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D002648:Child; D002675:Child, Preschool; D027081:DNA Gyrase / Q000235:genetics*; D027101:DNA Topoisomerase IV / Q000235:genetics*; D052978:Disk Diffusion Antimicrobial Tests; D024881:Drug Resistance, Bacterial / Q000235:genetics; D005260:Female; D024841:Fluoroquinolones / Q000494:pharmacology*; D000069443:Heptavalent Pneumococcal Conjugate Vaccine / Q000276:immunology*; D006801:Humans; D064704:Levofloxacin / Q000494:pharmacology*; D008297:Male; D008875:Middle Aged; D000077266:Moxifloxacin; D058885:Multilocus Sequence Typing; D011018:Pneumonia, Pneumococcal / Q000188:drug therapy* / Q000382:microbiology / Q000517:prevention & control; D011446:Prospective Studies; D065288:Serogroup; D013296:Streptococcus pneumoniae / Q000187:drug effects* / Q000276:immunology / Q000302:isolation & purification; D059005:Topoisomerase II Inhibitors / Q000494:pharmacology; D018074:Vaccines, Conjugate / Q000276:immunology*; D055815:Young Adult
chemical_list: D024841:Fluoroquinolones; D000069443:Heptavalent Pneumococcal Conjugate Vaccine; D059005:Topoisomerase II Inhibitors; D018074:Vaccines, Conjugate; D064704:Levofloxacin; D027101:DNA Topoisomerase IV; D027081:DNA Gyrase; D000077266:Moxifloxacin
keywords: Fluoroquinolone; Streptococcus pneumoniae; pneumococcal conjugate vaccine; resistance