Identification of Pasteurella multocida and Pasteurella haemolytica by API 20E, Minitek, and Oxi/Ferm systems.

Fifty serotyped isolates each of Pasteurella multocida and Pasteurella haemolytica were tested on the API 20E strip (Analytab Products, Plainview, N.Y.), the Oxi/Ferm tube (Roche Diagnostics, Nutley, N.J.), and the Minitek system (BBL Microbiology Systems, Cockeysville, Md.). None of the rapid test systems reliable identified these organisms. With the API system, discrepancies between expected and actual results for the oxidase test and nitrate test frequently resulted in misidentification or no identification. The Minitek system misidentified 68% of the P. haemolytica isolates. The Minitek identification of Pasteurella depends on 100% positive xylose reactions, whereas only 56% of the P. haemolytica strains were positive for xylose fermentation. The Oxy/Ferm system, instead of giving a definitive identification, in most instances merely placed Pasteurella in a category of similar organisms.