Enterobacteriaceae profile: Which combined statement best describes the typical biochemical capabilities of Enterobacteriaceae?

Introduction / Context:At the bench, a quick biochemical profile helps place an unknown Gram-negative rod within Enterobacteriaceae versus other families. A reliable quartet of reactions characterizes most members and guides further identification.

Given Data / Assumptions:

• Core reactions under consideration: catalase, oxidase, glucose fermentation, nitrate reduction.
• Family-level generalization (allowing for rare exceptions) is intended.
• Testing is performed under standard conditions.

Concept / Approach:Enterobacteriaceae are facultative anaerobes that generally produce catalase, lack cytochrome c oxidase (oxidase-negative), ferment glucose (acid with or without gas), and reduce nitrate to nitrite via nitrate reductase. These features, taken together, help distinguish them from oxidase-positive non-fermenters (e.g., Pseudomonas) or from organisms that do not reduce nitrate.

Step-by-Step Solution: Consider catalase: usually positive in Enterobacteriaceae. Consider oxidase: characteristically negative, separating from many non-enteric rods. Consider glucose: fermentation is typical across the family. Consider nitrate: reduction to nitrite is commonly observed. Select the option that includes all four correct properties together.

Verification / Alternative check:Textbook identification matrices list this quartet as the starting point for Enterobacteriaceae workups before proceeding to IMViC, TSI slants, urease, and decarboxylases.

Why Other Options Are Wrong:

• Options with oxidase-positive or non-fermenter profiles describe non-enteric Gram-negative organisms.
• Claims of catalase negativity or absence of nitrate reduction do not fit the family profile.
• Restricting to lactose fermentation ignores non-lactose-fermenting enterics (e.g., Salmonella, Shigella).

Common Pitfalls:Equating lactose fermentation with family membership; lactose is variable, whereas glucose fermentation and oxidase negativity are more reliable family markers.

Final Answer:Catalase-positive, oxidase-negative, ferment glucose, reduce nitrate to nitrite.