violaceum is positive for catalase, nitrate reductase, and arginine dihydrolase it grows on sheep blood, MacConkey, chocolate, and Mueller-Hinton agar and it produces a deep purple pigment (violacein) that can result in black-appearing colonies. violaceum is a long, gram-negative, slightly curved bacillus. Most of these organisms are microaerophilic, facultatively anaerobic, somewhat fastidious, gram-negative bacilli that can appear pleomorphic or coccobacillary in direct smears or smears prepared from culture. recovered from environmental sources have been proposed. violaceum, and also is placed in the family Neisseriaceae certain other Chromobacterium spp. The genus Chromobacterium currently contains only 1 species of human significance, C. haemolytica now are named Mannheimia haemolytica. gallinarum now are named Avibacterium gallinarum, and some formerly classified as P. bettyae, may be reclassified as members of the genus Actinobacillus or other genera in the family Pasteurallaceae. is undergoing revision based on DNA-DNA hybridization studies and ribosomal RNA sequence analysis, and several species, including P. 1,2,6–8 The classification of Pasteurella spp. are rarely if at all associated with human disease. canis, P dagmatis, and P stomatis are other species isolated from humans. multocida, the most important species of human significance, can be separated into the subspecies multocida, septica, and gallicida. The taxonomy of the genus is in flux currently P. are oxidase and catalase positive, reduce nitrates, and use glucose and a variety of other carbohydrates. The genus Pasteurella contains several species of clinical significance and belongs to the family Pasteurellaceae along with the genera Aggregatibacter, Actinobacillus, Haemophilus, and Mannheimia. corrodens originally was thought to be related to the strictly anaerobic bacterium Bacteroides ureolyticus (formerly Bacteroides corrodens) because of the characteristic “corroding” or “pitting” of the surface of blood or chocolate agar by some isolates, suggesting a preference for anaerobic growth. The organism is oxidase positive and ornithine decarboxylase positive and reduces nitrates to nitrites, but it does not produce catalase, urease, or indole. corrodens is a small, straight rod that can appear coccobacillary. corrodens, which belongs to the family Neisseriaceae along with the genera Neisseria and Kingella. The genus Eikenella contains only 1 species, E. violaceum is motile and less fastidious than the others. Guliz Erdem, Amy Leber, in Principles and Practice of Pediatric Infectious Diseases (Fifth Edition), 2018 MicrobiologyĮikenella, Pasteurella, and Chromobacterium species display both common and contrasting characteristics of laboratory properties, epidemiology, and clinical presentations.
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