CDC group DF-2 is the vernacular name given to a slow-growing gram-negative 
bacterium that causes septicemia and meningitis in humans. Infections frequently 
(one-third of cases) occur following dog bites or close contact with dogs or 
occasionally with cats. Splenectomy and alcoholism appear to be strong 
predisposing factors for DF-2 infection. In addition to 150 DF-2 strains 
received for identification, we received 9 DF-2-like strains; 6 were isolated 
from wound or eye infections, 3 of which were associated with dog bites and 1 of 
which was associated with a cat scratch, and 3 were isolated from dog mouths. 
The major characteristics of DF-2 include production of acid but no gas from 
lactose and maltose and usually D-glucose; positive reactions for oxidase, 
catalase, arginine dihydrolase, gliding motility, and 
o-nitrophenyl-beta-D-galactopyranoside; growth enhanced by serum and by 
incubation in a candle jar atmosphere; and negative reactions for sucrose, 
raffinose, inulin, melibiose, nitrate reduction, indole, and growth on MacConkey 
agar. DF-2-like strains had the same characteristics, except that acid was 
formed from sucrose, raffinose, inulin, and melibiose. By the hydroxyapatite 
method, DNAs from 12 DF-2 strains were 88% related in 60 degrees C reactions and 
84% related in 75 degrees C reactions. Related sequences contained 0.5 to 1.5% 
unpaired bases (divergence). Three DF-2-like strains were 73 to 80% related at 
60 degrees C (with 2.0 to 2.5% divergence) and 68 to 75% related at 75 degrees 
C. The relatedness of DF-2 and DF-2-like strains was 19 to 31% at 60 degrees 
Celsius and 13 to 19% at 75 degrees Celsius. The relatedness of DF-2 and 
DF-2-like strains to Capnocytophaga species was 4 to 7%. The DNA relatedness 
date indicate that eh DF-2 and the DF-2-like strains are separate, previously 
undescribed species. Both groups are phenotypically and genetically distinct 
from Capnocytophaga species, although they do share several characteristics with 
Capnocytophaga species, including cellular morphology, gliding motility, 
cellular fatty acid composition, enhancement of growth in a candle jar 
atmosphere, and G+C content. The new species differ from Capnocytophaga species 
by their positive oxidase and catalase reactions. We chose to avoid creating a 
new genus and proposed the names Capnocytophaga canimorsus sp. nov. for group 
DF-2 and C. cynodegmi sp. nov. for the DF-2-like strains.