Coliform definition check: Which of the following genera are included among the lactose-fermenting, Gram-negative coliform bacilli used as indicators of fecal contamination in water and food microbiology?

Introduction / Context:
Coliforms are a practical indicator group in environmental and food microbiology. They are Gram-negative, non-spore-forming rods that ferment lactose with acid and gas within 48 hours at appropriate temperatures. Recognizing the principal genera classified as coliforms is essential for interpreting water quality tests and hygiene monitoring.

Given Data / Assumptions:

• Genera considered: Escherichia, Klebsiella, Enterobacter.
• Coliform criteria focus on lactose fermentation and specific biochemical traits.
• We are using conventional microbiological definitions used in applied testing.

Concept / Approach:
Escherichia (especially E. coli), Klebsiella, and Enterobacter are classic coliform genera. E. coli is the best indicator of fecal contamination (thermotolerant coliform), while Klebsiella and Enterobacter may also originate from environmental sources but still fall under the broader coliform umbrella.

Step-by-Step Solution:
Identify the core coliform traits: lactose fermentation, Gram-negative rod, oxidase negative.Map the listed genera to these traits.All three genera meet the coliform definition.Select the inclusive option.

Verification / Alternative check:
Multiple standard methods (MPN, membrane filtration with selective/differential media) enumerate these genera as coliforms in water testing guidelines.

Why Other Options Are Wrong:
Picking any single genus would exclude other valid coliforms; the question seeks completeness.

Common Pitfalls:
Confusing total coliforms with fecal (thermotolerant) coliforms; E. coli is the most specific fecal indicator.

Final Answer:
All of these