📌 Definition The Multiple Tube Method (also called the Most Probable Number – MPN method) is a statistical method used to estimate the number of coliform bacteria in water by observing growth patterns in serial dilutions. 🧪 Principle (Core Concept) Coliforms (e.g., Escherichia coli) ferment lactose → acid + gas Gas is detected in Durham tubes Number of positive tubes → statistical estimation (MPN) 👉 Important: MPN is not a direct count, but a probability-based estimate 🧪

Definition Assessment of microbial quality using indicator organisms rather than direct pathogen detection Why not detect pathogens directly? Low numbers: Pathogens are often present in very small quantities in samples, making direct detection difficult without prior concentration. Intermittent presence: Pathogens may not be consistently present in every sample at all times, leading to false-negative results if sampling misses them. Wide variety: Numerous different patho