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I have isolated a gram negative bacillus, oxidase negative, catalase negative, onpg positive, grows in CO2 and anaerobically, glucose positive, maltose positive, sucrose positive, trehalose positive, nitrate negative, esculin negative mannitol negative, ornithine negative, lysine negative, arginine negative, no growth on macconkey and non motile. What is it?
More information - vitek 2 identified this as Sphingomonas paucimobilus but it is esculin negative. Grows on blood agar and chocolate well at 48 hours. Isolated from the blood of a cancer patient.
Thank you
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You first have to determine if it is a fermenter or a non-fermenter. It could be a fastidious fermenter like one of the HACEK organisms. Haemophilus aphrophilus and Actinobacillus are both oxidase negative. Check the catalse, both these organisms are catalase negative as well. H. aphrophilus is ONPG positive so this is a possiblity. If you think it is a fastidious fermenter, try putting it on one of the Neisseria-Hemophilus test kits. If it is esculin negative then it is not Sphingomonas paucimobilis, plus S. paucimobilis produce yellow pigmented colonies. The only non-fermenters that are both oxidase-negative and non-motile belong to the Acinetobacter group but these all grow on MacConkey. My guess is that you are dealing with one of the fastidious fermenters. Consult a good textbook for further characteristics of the fastidious fermenters. We suggest Konemans color Atlas and Textbook of Diagnostic Microbiology, 6th ed.
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