Microbiological analysis of water — choosing an evaluation method Because it works with many media types and permits a resuscitation step for stressed cells, which technique has become a common, often preferred method for assessing the microbiological quality of water?

Introduction / Context:
Drinking-water and recreational-water testing must recover low numbers of injured or stressed bacteria while enabling identification on selective media. The method chosen influences sensitivity, specificity, processing time, and the ability to confirm organisms like coliforms and E. coli.

Given Data / Assumptions:

• We need a method compatible with varied culture media.
• The method should allow a short resuscitation step to recover chlorine-stressed or otherwise injured bacteria.
• Routine water labs often process large volumes for low targets.

Concept / Approach:
Membrane filtration (MF) concentrates organisms by vacuum onto a 0.45 μm membrane, which is then placed on non-selective or selective/differential agar. A brief non-selective resuscitation step can improve recovery of stressed cells before exposure to selective agents. MF supports numerous media (for example, mEndo for total coliforms, mTEC for E. coli, mFC for thermotolerant coliforms) and is widely standardized.

Step-by-Step Solution:
Identify the method matching all clues: MF handles many media and enables resuscitation.Contrast with MPN: valuable but less flexible for plate-based differentiation and may be less efficient for very large volumes.Exclude Winogradsky (an enrichment model, not a regulatory testing method) and stand-alone MUG or direct counts, which lack comprehensive culture confirmation.Choose membrane filtration.

Verification / Alternative check:
Standard methods (for example, APHA Standard Methods) detail MF as a preferred approach for total coliforms/E. coli in many regulatory settings.

Why Other Options Are Wrong:
MPN is common but does not inherently include a plate-based resuscitation step; Winogradsky is educational; MUG alone is a biochemical screen; direct counts detect both viable and non-viable cells.

Common Pitfalls:
Believing MPN is always superior; in many cases MF offers better precision and differentiation when sample clarity and volume allow.

Final Answer:
Membrane filtration with culture on selective/differential media.