The aim of the study was to determine if
immunomodulation of host defense with recombinant murine
granulocyte colony-stimulating factor (
G-CSF) improves the efficacy of
trovafloxacin or
moxifloxacin in
abscesses containing Bacillus fragilis ATCC 23745 and different Escherichia coli strains varying in virulence. Treatment of mice inoculated with 10(7) CFU B. fragilis and 10(5) CFU low-virulence E. coli with either
trovafloxacin (150 mg/kg/day every 24 hours, days 3 to 7) or
moxifloxacin (96 mg/kg/day every 12 hours, days 3 to 7), significantly reduced the number of B. fragilis to 6.9 +/- 0.35 and 5.8 +/- 0.10 and that of E. coli to 4.9 +/- 0.09 and 4.2 +/- 0.07 log CFU/
abscess for
trovafloxacin and
moxifloxacin, respectively, compared to controls (B. fragilis 8.7 and E. coli 7.4 log CFU/
abscess) on day 8. Also,
moxifloxacin was more potent than
trovafloxacin. Addition of
G-CSF prophylaxis (1 mug once on day -1) or
therapy (1 mug/day on days 3 to 7) to
fluoroquinolone treatment did not improve the efficacy of
fluoroquinolone therapy alone. The effect of
moxifloxacin with or without
G-CSF prophylaxis on
abscesses with a virulent hemolytic E. coli strain was also studied. In
moxifloxacin-treated mice, 75% survived
infection compared to 10% of controls. Combining
moxifloxacin with
G-CSF prophylaxis significantly decreased survival (30%) compared to
moxifloxacin alone. In addition,
G-CSF prophylaxis resulted in a threefold (E. coli) to 100-fold (B. fragilis) increased outgrowth in the
abscesses of surviving mice. In conclusion, the addition of
G-CSF to a
fluoroquinolone is not advisable since, depending on the virulence of the E. coli strains, this might detrimentally influence the outcome of
therapy.