Characteristics and biotypes of Pasteurella multocida isolated from humans.

Fifty-two isolates of Pasteurella (48 strains of Pasteurella multocida and 4 strains of atypical Pasteurella) were identified by conventional and commercial test systems. All strains fermented glucose, sucrose, and fructose in purple broth base (Difco Laboratories) with bromocresol purple as indicator, although the atypical Pasteurella produced fermentation reactions that were barely perceptible. Eleven different biotypes were identified by fermentation reactions in maltose, mannitol, xylose, sorbitol, and trehalose media. There was a correlation of biotypes to cat bites, with 61% of cat bite isolates falling into biotype A and B. A correlation of biotype and dog bite isolates was not seen. The choice of medium used for fermentation tests was critical as evidenced by the inability of the organisms to grow in a second commercially purchased preparation of purple broth base. The reliability of commercial test systems in identifying Pasteurella was 81% for Oxi/Ferm (Roche Diagnostics, Div. Hoffmann-La Roche, Inc., Nutley, N.J.), 68% for API (Analytab Products, Plainview, N.Y.), and 11% for Minitek (BBL Microbiology Systems, Cockeysville, MD.).