Which group of tests best identifies Morganella and Proteus genera?

• A. Motility, urease, and phenylalanine deaminase
• B. Malonate, glucose fermentation, and deoxyribonuclease (DNase)
• C. Indole, oxidase, MR, and VP
• D. Indole, citrate, and urease

Answer: (A)

The identification of Morganella and Proteus genera is effectively accomplished through testing for motility, urease, and phenylalanine deaminase.

Motility is a crucial characteristic as both genera are known to be motile, allowing for differentiation from non-motile organisms. Urease production is significant because both Morganella and Proteus species are urease-positive, meaning they can hydrolyze urea to ammonia, leading to an increase in pH and a change in the medium's color. Phenylalanine deaminase activity is also an important marker; the ability to deaminate phenylalanine is a distinctive trait that helps to differentiate these genera, particularly Proteus, from others that do not possess this ability.

The other groups of tests mentioned include different biochemical reactions that are more suited for other genera within the Enterobacteriaceae family or do not specifically highlight the characteristics unique to Morganella and Proteus. Therefore, the combination of motility, urease activity, and phenylalanine deaminase testing provides a reliable method for identifying these two genera effectively.