title: High frequency of fluoroquinolone- and macrolide-resistant streptococci among clinically isolated group B streptococci with reduced penicillin susceptibility.
abstract: OBJECTIVE
  Recently several clinical isolates of Streptococcus agalactiae [also known as group B Streptococcus (GBS)] that have acquired reduced penicillin susceptibility (PRGBS) by amino acid substitutions in the penicillin-binding protein 2X have emerged. The frequency of fluoroquinolone (FQ)- and macrolide-resistant streptococci among PRGBS is not yet known.
  
  
  METHODS
  Fifty-seven GBS [19 PRGBS and 38 penicillin-susceptible GBS (PSGBS)], isolated from different medical institutions in Japan, were studied. For GBS, the MICs of penicillin G, levofloxacin and erythromycin were determined using the agar dilution method. Nineteen PRGBS were previously confirmed as genetically diverse streptococci by PFGE. Further, the mechanisms underlying penicillin, FQ and macrolide non-susceptibility/resistance were analysed.
  
  
  RESULTS
  The frequency of non-susceptibility to FQs among PSGBS was 18.4% (7/38), whereas that among PRGBS was 100% (19/19). The frequency of resistance to erythromycin among PSGBS was 7.9% (3/38), while that among PRGBS was 47.4% (9/19). Statistical significance was determined using Fisher's exact test between reduced penicillin susceptibility and FQ non-susceptibility (P ≤ 0.0001) and macrolide resistance (P=0.0012). The resistance/non-susceptibility mechanisms among PRGBS were diverse, suggesting that the PRGBS examined were not clonal.
  
  
  CONCLUSIONS
  PRGBS isolates tend to show resistance to FQs and/or macrolides. Because the drug choice for treating these multidrug-resistant GBS is more limited than that for usual GBS, these strains may present future public health challenges.
authors.affiliation: Department of Bacteriology, Nagoya University Graduate School of Medicine, Nagoya, Aichi 466-8550, Japan. koujikim@med.nagoya-u.ac.jp
authors.forename: Kouji
authors.initials: K
authors.lastname: Kimura
authors.forename: Noriyuki
authors.initials: N
authors.lastname: Nagano
authors.forename: Yukiko
authors.initials: Y
authors.lastname: Nagano
authors.forename: Satowa
authors.initials: S
authors.lastname: Suzuki
authors.forename: Jun-ichi
authors.initials: J
authors.lastname: Wachino
authors.forename: Keigo
authors.initials: K
authors.lastname: Shibayama
authors.forename: Yoshichika
authors.initials: Y
authors.lastname: Arakawa
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial; D016521:Electrophoresis, Gel, Pulsed-Field; D024841:Fluoroquinolones / Q000494:pharmacology*; D006801:Humans; D007564:Japan / Q000453:epidemiology; D018942:Macrolides / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D058889:Molecular Typing; D010406:Penicillins / Q000494:pharmacology; D015995:Prevalence; D013290:Streptococcal Infections / Q000453:epidemiology* / Q000382:microbiology*; D013292:Streptococcus agalactiae / Q000145:classification / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification
chemical_list: D000900:Anti-Bacterial Agents; D024841:Fluoroquinolones; D018942:Macrolides; D010406:Penicillins