2002
Ocular Microbiology and Immunology Group, Abstract 3
OMIG
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Susceptibility
of Ocular Isolates to Gatifloxacin and Older Fluoroquinolones
Monica Monica, MD1; Harold Jensen, PhD2; The Allergan Gatifloxacin
Study Group2
1Private Practice, New Orleans, LA; 2Allergan
Purpose:
To determine susceptibility of ocular isolates to the 4th generation
fluoroquinolone, gatifloxacin, and to the 3rd generation fluoroquinolones,
levofloxacin and ciprofloxacin.
Methods:
Conjunctival swabs were taken from patients with bacterial conjunctivitis
in a clinical trial of gatifloxacin, prior to any antibacterial
therapy. MICs for individual isolates from the swabs were classified
using NCCLS susceptibility breakpoints.
Results:
All Gram-positive ocular isolates (n=170) were susceptible to gatifloxacin,
except for a single strain of Staphylococcus haemolyticus which
displayed intermediate resistance. In contrast, 1.8% and 8.8% of
Gram-positives were resistant in an intermediate range, and 2.9%
and 7.6% were fully resistant, to levofloxacin and ciprofloxacin,
respectively. All isolates of Staphylococcus epidermidis (n=38),
a species frequently encountered in ocular infections, were susceptible
to gatifloxacin. However, 10.5% and 15.8% of S. epidermidis ocular
isolates were resistant to levofloxacin and ciprofloxacin respectively,
and another 5.3% showed intermediate resistance to levofloxacin.
The MIC90 for S. epidermidis ocular isolates was 2.0 µg/ml
for gatifloxacin compared to 8.0 and 32.0 µg/ml for levofloxacin
and ciprofloxacin, respectively. For Streptococcus pneumoniae (n=30),
the MIC90 was 0.25 µg/ml for gatifloxacin, compared to 1.0
µg/ml for levofloxacin and ciprofloxacin. All of the Gram-negative
isolates (n=65) were susceptible to all 3 antibacterials.
Conclusions:
Substantial percentages of Gram-positive species isolated from bacterial
conjunctivitis patients were resistant or partially resistant to
levofloxacin and ciprofloxacin, however, the same strains were susceptible
to the 4th generation fluoroquinolone, gatifloxacin. Compared to
older fluoroquinolones, gatifloxacin displays clearly improved activity
against Gram-positive ocular isolates in vitro.
This research
was supported by funding from Allergan Inc.
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