Prevalence of Ile-460-Val/ParE substitution in clinical Streptococcus pneumoniae isolates that were less susceptible to fluoroquinolones.
A total of 73 clinical isolates of Streptococcus pneumoniae were measured for susceptibilities to nine fluoroquinolones, and nucleotide sequences of the quinolone resistance-determining regions (QRDRs) were determined. MIC90s of sparfloxacin, tosufloxacin, grepafloxacin, and gatifloxacin were less than 0.5 mg/L and the MIC90 of ciprofloxacin was 2 mg/L, although MIC values of some isolates to ciprofloxacin were more than 2 mg/L. We found that 60 of 73 isolates had only Ile-460-Val/ParE substitution and two isolates had an additional substitution of Ser-114-Gly/GyrA, while none of the isolates had any other substitutions in QRDRs of either ParC/E or GyrA/B. The isolates carrying Ile-460-Val/ParE substitution were more resistant to the fluoroquinolones norfloxacin and ciprofloxacin than the isolates with no amino acid substitution and the differences in MIC values were significant, suggesting that Ile-460-Val/ParE substitution in recent clinical S. pneumoniae isolates should be involved in the low-level fluoroquinolone resistance.
Kawamura-Sato
Kumiko
K
Department of Medical Technology, Nagoya University Graduate School of Health Science, 1-1-20, Daikominami, Nagoya, Aichi, 461-8673, Japan. kumiko@met.nagoya-u.ac.jp
Hasegawa
Tadao
T
Torii
Keizo
K
Ito
Hideo
H
Ohta
Michio
M
D019943:Amino Acid Substitution / Q000235:genetics; D027101:DNA Topoisomerase IV / Q000235:genetics*; D004352:Drug Resistance, Microbial / Q000235:genetics*; D024841:Fluoroquinolones / Q000494:pharmacology*; D006801:Humans; D008826:Microbial Sensitivity Tests; D009154:Mutation; D015995:Prevalence; D013296:Streptococcus pneumoniae / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification
D024841:Fluoroquinolones; D027101:DNA Topoisomerase IV