The laboratory investigation reflects the presence of an infection with neutrophilia and bandemia; and in severe cases, sepsis with multiorgan failure develops. The diagnosis is based on the blood culture results, but unfortunately it is correctly identified in less than a third of cases, likely due to lack of familiarity with the organism and its special growth media characteristics. C canimorsus, which is found in the neutrophil, has characteristic, filamentous, rod-shaped morphology. Also reported are fingerlike projections along the agar surface due the unique motility of the bacteria. The culture conditions are specific; with the organism growing optimally at temperatures of 35 to 37° in an anaerobic atmosphere with 5 to 10% CO2 or in an anaerobic atmosphere, and on Columbia agar with 5% sheep blood or standard chocolate agar. It does not grow on MacConkey agar. Fermentation of glucose, lactose, and maltose is often observed but not of raffinose. The major phenotypic characteristics of C canimorsus include positive test results for oxidase, catalase, arginine dihydrolase, and o-nitrophenyl-β-d-galactopyranoside and negative reactions for urease, nitrates, and indole.