Description of Human-Derived Centers for Disease Control Coryneform Group 2 Bacteria as Actinomyces bernardiae sp. nov.

Abstract

Biochemical, chemotaxonomic, and molecular methods were used to establish the precise taxonomic position of the Centers for Disease Control (CDC) coryneform group 2 bacteria. The results of a comparative 16s rRNA sequence analysis demonstrated that the CDC coryneform group 2 bacteria constitute a distinct species within the genus Actinomyces. Actinomyces pyogenes was found to be the closest genealogical relative of the CDC coryneform group 2 bacteria, although these taxa were readily distinguished from each other and other Actinomyces spp. by using phenotypic criteria. On the basis of our findings we propose the name Actinomyces bernardiae sp. nov. for the CDC coryneform group 2 bacteria. The type strain is DSM 9152 (CCUG 33419).Within the last few years, clinical microbiologists have become more aware of asporogenous, gram-positive rods as these bacteria have been encountered more frequently in clinical specimens. The taxonomic position of an individual strain, however, is often unclear (8,27). In 1987, workers at the Special Bacteriology Reference Laboratory at the Centers for Disease Control and Prevention (CDC) designated some coryneform bacteria that were referred to this laboratory CDC coryneform group 2 bacteria (19). This taxon was established on the basis of morphological, biochemical, and chemical properties that separated its members from all previously described gram-positive rods (19). The initial 11 isolates belonging to CDC coryneform group 2 came from various clinical sources (e.g., blood, wounds, or the urinary tract). To our knowledge, no other report on CDC coryneform group 2 bacteria has appeared since the primary description of this taxon. As the precise taxonomic position of CDC coryneform group 2 was unclear, we conducted the study described below; in this study we used biochemical, chemotaxonomic, and molecular methods. MATERIALS AND METHODSBacterial strains. The origins of the strains which we used and their clinical sources are shown in Table 1. These strains were obtained from the National Laboratory for Bacteriology, Laboratory Center for Disease Control, Ottawa, Canada, from the Special Bacteriology Reference Laboratory, CDC, Atlanta, Ga., and from the Department of Medical Microbiology, University of Zurich, Zurich, Switzerland.Morphological and biochemical characteristics. Strains were grown aerobically at 37°C in an atmosphere containing 5% C02 on Columbia agar supplemented with 5% sheep blood (all media were obtained from Becton Dickinson Microbiology Systems, Cockeysville, Md., unless indicated otherwise). The same medium was used to assess growth in a strictly anaerobic atmosphere (10). The methods used for biochemical profiling have been described previously (9).Commercial API ZYM (enzymatic profiling) and API 50CH (carbohydrate fermentation) systems (both obtained from API bioMtrieux, Marcy l'Etoile, France) were used according to the instructions provided by the manufacturer. Antimicrobial agent susceptibility testing. The MICs of eight antimicrobial agents (ciprofloxacin, c...

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