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Phone: 33 1 60 81 58 Fax: 33 1 60 81 58 E-mail: jean-winoc. A real-time PCR assay with locked nucleic acid probes was developed to screen mutations at codons 79 and 83 of the Streptococcus pneumoniae parC gene. Only silent mutations were detected among French invasive fluoroquinolone-susceptible strains.
This test could be useful for some high-risk patients or in national surveys. The worldwide spread of multidrug-resistant clones has led to the increasing use of fluoroquinolones FQs in the therapy of Streptococcus pneumoniae infections In some countries the increase of FQ resistance FQR in that species and some clinical failures have been reported 5 , 9 , 13 , 16 , The low-level resistance first-step parC mutants FSPC were implicated in the selection following levofloxacin therapy of the highly resistant parC-gyrA double mutants 7 , FSPC mutants are classified as susceptible to FQs according to the standard breakpoints 19 , 26 , 27 , This assay was tested for an epidemiological survey that included a panel of controls and S.
Control strains including wild-type and ParC mutant strains were tested repeatedly Table 1. The MICs were determined by an agar dilution method and interpreted according to Clinical and Laboratory Standards Institute guidelines as previously described 11 , 12 , 22 , A mutation was suspected if at least one probe failed to hybridize. Z as a reference. Only the reported mutations were identified in the whole QRDR of the control strains. Nucleotide positions in the parC gene of Streptococcus pneumoniae from GenBank accession no.
The control strains showed reliable hybridization results data not shown. All clinical strains were susceptible to levofloxacin, and 6. The PCR results were confirmed by the sequencing: a silent mutation in one target site 11 strains and mutation inside the sequences recognized by the probes codon 77, 81, or 86; 5 strains or the primers codon 91 or 95; 2 strains showing no increase in the MICs of FQs.
