[Results from a German interlaboratory test to establish the broth microdilution method for the determination of the minimum inhibitory concentration of bacteria from animals].
In accordance with NCCLS guideline M31-A2, the DVG working group "antimicrobial resistance" developed a standard operating procedure (SOP) for the determination of the minimal inhibitory concentration (MIC) of antimicrobial agents by broth microdilution. This SOP was evaluated for its fitness for use in a national interlaboratory test. A total of 32 participating laboratories tested five strains (including two internationally accepted reference strains and three field strains representing in total three different bacterial species) three times at a one week interval each, using uniform microtitre plates. In 31 of the 32 laboratories more than 80% of MIC determinations performed yielded values in the expected range. In total 94.0% of the results were reproducible, with a lesser deviation of 4.0% from the expected values for laboratories performing MIC determination as a matter of routine (46.9%), compared to 7.9% for laboratories without such routine (53.1%). Comparing the consistency of results on the basis of the tested strains, a higher reproducibility of the results was observed for reference strains (96.1%) than for field strains (92.6%). In particular results obtained for the Streptococcus uberis field strain were afflicted with a higher error ratio (98 deviations from the expected values). Among the tested antimicrobial agents, a higher variability of results was recorded only for gentamicin with 16.7% divergent MIC determinations (mean value 6.0%). The high reproducibility of the results confirmed by this interlaboratory study underlines the robustness of the developed SOP as well as broth microdilutions as the method of choice for MIC determina tion.
Wallmann
Jürgen
J
Bundesamt für Verbraucherschutz und Lebensmittelsicherheit, Berlin. juergen.wallmann@bvl.bund.de
Böttner
Alexander
A
Hafez
H Mohamed
HM
Kehrenberg
Corinna
C
Kietzmann
Manfred
M
Klarmann
Dieter
D
Klein
Günter
G
Krabisch
Peter
P
Kühn
Tilman
T
Luhofer
Gabriele
G
Richter
Angelika
A
Schwarz
Stefan
S
Sigge
Claudia
C
Traeder
Wolfgang
W
Waldmann
Karl-Heinz
KH
Werckenthin
Christiane
C
Zschiesche
Eva
E
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology* / Q000627:therapeutic use; D001419:Bacteria / Q000187:drug effects* / Q000254:growth & development; D001424:Bacterial Infections / Q000188:drug therapy / Q000382:microbiology / Q000662:veterinary*; D019411:Clinical Laboratory Techniques / Q000592:standards*; D024881:Drug Resistance, Bacterial; D005858:Germany; D008826:Microbial Sensitivity Tests / Q000592:standards / Q000662:veterinary*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D000900:Anti-Bacterial Agents