Reliability of the E-test method for detection of colistin resistance in clinical isolates of Acinetobacter baumannii.
We compared the E-test to the broth microdilution method for testing the susceptibility of 115 clinical isolates of Acinetobacter baumannii to colistin. Twenty-two (19.1%) strains were resistant to colistin and 93 (80.8%) strains were susceptible according to the reference broth microdilution method. A categorical agreement of 98.2% was found, with only two (1.7%) very major errors. Agreement within 1 twofold dilution between the E-test and the broth microdilution was 16.5%. Complete agreement was found for the strains for which MICs fell within the range of 0.25 to 1 microg of colistin/ml. However, there was poor concordance, particularly in extreme dilutions with higher MICs by the E-test method.
Arroyo
L A
LA
Clinical Microbiology, University Hospitals Vírgen del Rocío, Seville, Spain. larroyo@us.es
García-Curiel
A
A
Pachón-Ibañez
M E
ME
Llanos
A C
AC
Ruiz
M
M
Pachón
J
J
Aznar
J
J
D000151:Acinetobacter Infections / Q000382:microbiology*; D040981:Acinetobacter baumannii / Q000187:drug effects*; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D003091:Colistin / Q000494:pharmacology*; D024881:Drug Resistance, Bacterial; D006801:Humans; D008826:Microbial Sensitivity Tests / Q000379:methods
D000900:Anti-Bacterial Agents; D003091:Colistin