Activity of the new fluoroquinolone trovafloxacin (CP-99,219) against DNA gyrase and topoisomerase IV mutants of Streptococcus pneumoniae selected in vitro

Abstract

The MICs of trovafloxacin, ciprofloxacin, ofloxacin, and sparfloxacin at which 90% of isolates are inhibited for 55 isolates of pneumococci were 0.125, 1, 4, and 0.5 microgram/ml, respectively. Resistant mutants of two susceptible isolates were selected in a stepwise fashion on agar containing ciprofloxacin at 2 to 10 times the MIC. While no mutants were obtained at the highest concentration tested, mutants were obtained at four times the MIC of ciprofloxacin (4 micrograms/ml) at a frequency of 1.0 x 10(-9). Ciprofloxacin MICs for these first-step mutants ranged from 4 to 8 micrograms/ml, whereas trovafloxacin MICs were 0.25 to 0.5 microgram/ml. Amplification of the quinolone resistance-determining region of the grlA (parC; topoisomerase IV) and gyrA (DNA gyrase) genes of the parents and mutants revealed that changes of the serine at position 80 (Ser80) to Phe or Tyr (Staphylococcus aureus coordinates) in GrlA were associated with resistance to ciprofloxacin. Second-step mutants of these isolates were selected by plating the isolates on medium containing ciprofloxacin at 32 micrograms/ml. Mutants for which ciprofloxacin MICs were 32 to 256 micrograms/ml and trovafloxacin MICs were 4 to 16 micrograms/ml were obtained at a frequency of 1.0 x 10(-9). Second-step mutants also had a change in GyrA corresponding to a substitution in Ser84 to Tyr or Phe or in Glu88 to Lys. Trovafloxacin protected from infection mice whose lungs were inoculated with lethal doses of either the parent strain or the first-step mutant. These results indicate that resistance to fluoroquinolones in S. pneumoniae occurs in vitro at a low frequency, involving sequential mutations in topoisomerase IV and DNA gyrase. Trovafloxacin MICs for wild-type and first-step mutants are within clinically achievable levels in the blood and lungs of humans.

Type II Topoisomerases as Targets for Quinolone Antibacterials Turning Dr. Jekyll into Mr. Hyde

“…With hindsight, it is it is easy to understand why this approach was unsuccessful. Recent evidence indicates that DNA gyrase is not the primary cytotoxic target for most quinolones in Grampositive species; rather, it is topoisomerase IV [1,3,4,15,17,18,22,83,84]. This change in target probably reflects the increased sensitivity of Grampositive topoisomerase IV to quinolone-based compounds coupled with the fact that DNA gyrase found in these bacteria are considerably less sensitive to these drugs than their Gram-negative counterparts [3,22,77,78,82,85,86].…”

“…Quinolones are targeted to the prokaryotic type II topoisomerases, DNA gyrase and topoisomerase IV [2,4,7,[9][10][11][12][13][14][15][16][17][18][19][20][21][22]. The founding member of this drug family, nalidixic acid (Fig.…”

Class-dependent relevance of tissue distribution in the interpretation of anti-infective pharmacokinetic/pharmacodynamic indices

“…The fluoroquinolones prevent DNA replication by inhibiting type II topoisomerases, also called DNA gyrase, and topoisomerase IV [48,49] and may also affect bacterial membranes [50]. Like the aminoglycosides, the fluoroquinolones display concentrationdependent killing [7] and both the AUC 0-24 /MIC and C max /MIC ratios are correlated with efficacy.…”

Fluoroquinolones Inhibit PreferentiallyStreptococcus pneumoniaeDNA Topoisomerase IV Than DNA Gyrase Native Proteins

“…However, the new FQs, such as trovafloxacin D83. 11,16,22,27,36 ParE changes were found at D43531. Highand clinafloxacin, have greater in vitro activity against strepto-level Cpr strains had point mutations affecting both QRDRs of cocci32 and some of them are actually indicated for the treat-ParC and GyrA (S81, E85) 11,16,22,24,27,36 or ParE and GyrA.31 ment of pneumococcal infections.…”