Which of the following is NOT a rapid urease-positive genus of bacteria?

• A. Proteus
• B. Klebsiella
• C. Escherichia
• D. Helicobacter

Answer: (C)

Verified step by step guidance

1. Understand what 'rapid urease-positive' means: these bacteria produce the enzyme urease quickly, which hydrolyzes urea into ammonia and carbon dioxide, raising the pH and often detected by a color change in urease tests.
2. Recall that Proteus and Helicobacter are well-known for their rapid urease activity, which helps them survive in acidic environments like the stomach (Helicobacter) or urinary tract (Proteus).
3. Consider Klebsiella, which is also known to produce urease, although sometimes less rapidly than Proteus or Helicobacter, but still classified as urease-positive.
4. Evaluate Escherichia (such as E. coli), which generally does not produce urease rapidly or at all, making it urease-negative or very slow urease-positive compared to the others.
5. Conclude that among the listed genera, Escherichia is the one that is NOT rapid urease-positive, based on its typical enzymatic activity profile.