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Journal of Clinical Microbiology, December 1998, p. 3579-3584, Vol. 36, No. 12
Department of Pathology, Hershey Medical
Center, Hershey, Pennsylvania 17033,1 and
Department of Pathology, Case Western Reserve University,
Cleveland, Ohio 441062
Received 1 July 1998/Returned for modification 24 August
1998/Accepted 9 September 1998
The activities of levofloxacin and clarithromycin against 199 penicillin- and macrolide-susceptible and -resistant pneumococci were
tested by agar and microdilution methods in air and by disk diffusion
and E-test methods in air and CO2. For levofloxacin,
0095-1137/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Antipneumococcal Activities of Levofloxacin and
Clarithromycin as Determined by Agar Dilution, Microdilution,
E-Test, and Disk Diffusion Methodologies
99.0% of strains were susceptible at
2.0 µg/ml with zone
diameters of
17 mm, regardless of incubation in air or
CO2. Although zone sizes were smaller and E-test MICs were
higher for clarithromycin in CO2 than those in air,
category differences were minor, and susceptibility rates for
clarithromycin were similar to those obtained by agar and microdilution
in air (range, 76.9 to 80.9% by all methods). For clarithromycin,
adjustment of breakpoints based upon distribution of results resulted
in susceptibility rates which were similar by all methods (75.8 to
76.9% susceptible, 0 to 1.5% intermediate, 22.6 to 23.1% resistant).
Minor discrepancies were obtained with levofloxacin for one strain
(0.5%) by microdilution and two strains (1.0%) by disk diffusion in
CO2. For clarithromycin, minor discrepancies were found in
three strains (1.5%) by microdilution, seven strains (3.5%) by agar
dilution, four strains (2.0%) by E-test in air, six strains (3.0%) by
disk diffusion in air, and five strains (2.5%) by disk diffusion in
CO2. Major discrepancies occurred with levofloxacin in one
strain (0.5%) by microdilution but were not found with clarithromycin.
Very major discrepancies were not seen with levofloxacin, but occurred
with clarithromycin in five strains (2.5%) by microdilution, three
strains (1.5%) by agar dilution, two strains (1.0%) by E-test in air,
eight strains (4.0%) by disk diffusion in air, and one strain (0.5%)
by disk diffusion in CO2.
*
Corresponding author. Mailing address: Department of
Pathology, Hershey Medical Center, 500 University Dr., Hershey, PA
17033. Phone: (717) 531-5113. Fax: (717) 531-7953. E-mail:
pappelbaum{at}psghs.edu.
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