Journal of Antimicrobial Chemotherapy, Vol 40, 179-187, Copyright © 1997 by The British Society for Antimicrobial Chemotherapy
AF Schmalreck, I Kottmann, A Reiser, U Ruffer, R Schlenk, E Vanca and A Wildfeuer
The in-vitro activity of azithromycin, clarithromycin, erythromycin,
josamycin, midekamycin, roxithromycin and clindamycin against 674 Gram-
negative and Gram-positive clinical isolates, including methicillin-
resistant Staphylococcus aureus, was determined by agar dilution,
microdilution and agar diffusion with Mueller-Hinton medium according to
the Deutsches Institut fur Normung (DIN) 58940 guidelines. The results
obtained by regression analysis and the error-rate-bounded method of
Metzler-DeHaan indicate that common interpretative criteria (breakpoints)
for test discs may be assigned to susceptible/resistant Gram-positive
strains for all antibiotics tested. The following tentative DIN values are
suggested for 15 microg macrolide discs: for susceptible Gram-positive and
Gram-negative strains, an inhibition zone diameter (IZD) of > or = 26 mm
at a corresponding MIC of < or = 2 mg/L; for resistant Gram-positive
strains, an IZD of < or = 21 mm; for resistant Gram-negative strains, an
IZD of < or = 19 mm at a corresponding MIC of > or = 8 mg/L. For
Haemophilus influenzae only, breakpoints for azithromycin are suggested
with IZDs of > or = 21 mm for susceptible and < or = 18 mm for
resistant.
ORIGINAL ARTICLES
Susceptibility testing of macrolide and lincosamide antibiotics according to DIN guidelines. Deutsches Institut fur Normung
Microbiology Laboratories Research & Development, Pfizer/Mack, H. Mack Nachf., Illertissen, Germany.
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