CHARACTERISTICS OF ARTHROBACTER-CUMMINSII, THE MOST FREQUENTLY ENCOUNTERED ARTHROBACTER SPECIES IN HUMAN CLINICAL SPECIMENS

During a 2-year period, 10 strains of Arthrobacter cumminsii were isol ated in or received by a Swiss routine clinical bacteriology laborator y, and 5 further isolates were referred to a Swedish bacteriology refe rence center over a 5-year period, making A. cumminsii the most freque ntly encountered Arthrobacter species in these two laboratories. The p resent report outlines the clinical features of the 15 A. cumminsii st rains and presents an extended biochemical characterization of this mi croorganism. A. cumminsii exhibits a unique cellular fatty acid patter n with the consistent presence of C-14:0i and C-14:0 fatty acids as we ll as relatively large amounts of C-16:0i and C-16:0 fatty acids usual ly not seen in other Arthrobacter spp, Sodium dodecyl sulfate-polyacry lamide gel electrophoresis was found to be a useful tool for confirmat ion of the identification of A., cumminsii. The MICs of 39 antimicrobi al agents were determined, and it was demonstrated that aminoglycoside s and quinolones had only weak activities against A. cumminsii strains , in contrast to their activities against most other coryneform bacter ia. As a result of the extended characterization of A., cumminsii, an emended description of this species is presented. Due to the lack of A ., cumminsii in established identification systems, it is most likely that this species is underdiagnosed in many routine clinical bacteriol ogy laboratories.