In Vivo Selection of Streptococcus pneumoniae, Resistant to Quinolones, Including Sparfloxin

Twenty-one clinical isolates of Streptococcus pneumoniae showing reduced susceptibility or resistance to fluoroquinolones were characterized by serotype, antimicrobial susceptibility, and genetic analyses of the quinolone resistance-determining regions (QRDRs) of gyrA, gyrB, parC, and parE. Five strains were resistant to three or more classes of antimicrobial agents. In susceptibility profiles for gatifloxacin, gemifloxacin, levofloxacin, moxifloxacin, ofloxacin, sparfloxacin, and trovafloxacin, 14 isolates had intermediate- or high-level resistance to all fluoroquinolones tested except gemifloxacin (no breakpoints assigned). Fluoroquinolone resistance was not associated with serotype or with resistance to other antimicrobial agents. Mutations in the QRDRs of these isolates were more heterogeneous than those previously reported for mutants selected in vitro. Eight isolates had amino acid changes at sites other than ParC/S79 and GyrA/S81; several strains contained mutations in gyrB, parE, or both loci. Contributions to fluoroquinolone resistance by individual amino acid changes, including GyrB/E474K, ParE/E474K, and ParC/A63T, were confirmed by genetic transformation of S. pneumoniae R6. Mutations in gyrB were important for resistance to gatifloxacin but not moxifloxacin, and mutation of gyrA was associated with resistance to moxifloxacin but not gatifloxacin, suggesting differences in the drug-target interactions of the two 8-methoxyquinolones. The positions of amino acid changes within the four genes affected resistance more than did the total number of QRDR mutations. However, the effect of a specific mutation varied significantly depending on the agent tested. These data suggest that the heterogeneity of mutations will likely increase as pneumococci are exposed to novel fluoroquinolone structures, complicating the prediction of cross-resistance within this class of antimicrobial agents.

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confidence: 99%

Genetic Analyses of Mutations Contributing to Fluoroquinolone Resistance in Clinical Isolates of Streptococcus pneumoniae

Weigel¹,

Anderson²,

Facklam

et al. 2001

“…Not unexpectedly, however, it was possible to select mutants in vitro with decreased susceptibility and cross-resistance to other fluoroquinolones, including sparfloxacin (21,30,34). Strains of S. pneumoniae less susceptible to ofloxacin and ciprofloxacin were also isolated in vivo (3,29), and a trend toward increasing fluoroquinolone resistance in S. pneumoniae has been reported (10).…”

mentioning

confidence: 99%

High-level fluoroquinolone resistance in Streptococcus pneumoniae requires mutations in parC and gyrA

Janoir

Zeller

Kitzis

et al. 1996

219

The mechanism of high-level fluoroquinolone resistance was studied in strains of Streptococcus pneumoniae, either selected in vitro or isolated from clinical samples. By using DNA from these high-level-resistant strains, low-level-resistant transformants (MIC of pefloxacin, > or = 32 micrograms/ml; MIC of ciprofloxacin, 4 micrograms/ml; MIC of sparfloxacin, 0.50 micrograms/ml) were obtained at high frequencies (ca.10(-2)), while high-level-resistant transformants (MIC of pefloxacin, > or = 64 micrograms/ml; MIC of ciprofloxacin, 16 to 64 micrograms/ml; MIC of sparfloxacin, > or = 8 micrograms/ml) were obtained only at low frequencies (ca.10(-4)). This suggested that mutations in at least two unlinked genes were necessary to obtain high-level resistance. Low-level resistance was associated with ParC mutations (change from Ser to Tyr at position 79 [Ser79Tyr], Ser79Phe, or Asp83Gly). ParC mutations were associated, in high-level-resistant strains and transformants, with alterations in the quinolone resistance-determining region of GyrA (Ser84Tyr, Ser84Phe, and/or Glu88Lys). Low-level resistance was shown to be necessary for expression of the gyrA mutations. No mutation in the region corresponding to the quinolone resistance-determining region of GyrB and no alteration of drug accumulation were found.

“…Clinical failures due to fluoroquinolone-resistant organisms have occurred when either ciprofloxacin or ofloxacin was used to treat respiratory tract infections (4,27,28). Epidemiological studies have identified resistance in S. pneumoniae with mutated gyrase and topoisomerase IV genes (10,34,35), but efflux may also cause fluoroquinolone resistance (1, 6-8, 13, 14, 19, 30, 36, 37, 46).…”

mentioning

confidence: 99%

Global Transcriptome Analysis of the Responses of a Fluoroquinolone-Resistant Streptococcus pneumoniae Mutant and Its Parent to Ciprofloxacin

Marrer

Satoh

Johnson

et al. 2006

Streptococcus pneumoniae M22 is a multidrug-resistant mutant selected after exposure of capsulated wildtype S. pneumoniae NCTC 7465 (strain M4) to ciprofloxacin. DNA microarray analysis comparing the gene expression profiles of strain M22 with those of strain M4 showed that strain M22 constitutively expressed 22 genes at levels higher than those observed in strain M4 under all conditions studied. These included the genes encoding the enzymes involved in branched-chain amino acid biosynthesis and two genes (patA and patB) with sequences suggestive of ABC transporter proteins. Expression of the patA and patB genes was induced by ciprofloxacin in both strains, but in strain M4 it only reached the levels observed in strain M22 after long incubation with high concentrations of ciprofloxacin. The altered expression profile observed with strain M22 suggested that the mutation or mutations acquired during resistance selection bring the cell into a state in which the expression of critical genes is preemptively altered to correct for the potential effects of ciprofloxacin on gene expression in the parent strain.