Quantitative Microbiology Testing: E. coli Enumeration using Fluorogenic Indicator Kit
📌 The demonstration focuses on quantitative microbiological testing for E. coli count in food using a ready-to-use media kit based on binary detection technology utilizing a fluorogenic indicator.
🔬 The kit's working principle involves the growth of *E. coli* after inoculation into wells containing a medium that changes color and fluoresces under UV light due to the enzymatic reaction of $\beta$-glucuronidase.
📊 The final *E. coli* count is determined by using a conversion table provided by the manufacturer based on the number of positive wells after incubation.

Sample Preparation and Media Handling
🧴 The testing procedure requires preparing materials according to the National Drug and Food Testing Development Center analysis method number 35 of 2019 for *E. coli* enumeration.
🧪 Sample preparation involves cleaning the packaging with 70% alcohol, compositing 25 grams of the sample (except fresh fruit) aseptically into a sterile stomacher bag, and homogenizing it with 225 mL of Peptone Saline Solution (PSS).
💧 Before use, the reconstituted media must be tapped on the palm to ensure complete dissolution of the powder, followed by mixing 1 mL of the diluted sample into the media before aliquoting into the wells.

Incubation and Result Interpretation
🌡️ After incubation, wells showing a color change from blue to pink accompanied by fluorescence under a 366 nm UV light at a distance of 15 to 30 cm (6 to 12 inches) indicate the presence of *E. coli*.
🧫 The entire mixture must be poured evenly across the middle of the wells, ensuring no bubbles are present in any hole, and excess liquid is poured off.
📈 The final *E. coli* count is calculated by referring to the conversion table corresponding to the number of positive wells, as detailed in Method Number 35 of 2019.

Key Points & Insights
➡️ Adhere strictly to the approved standard method (National Drug and Food Testing Development Center number 35 of 2019) for accurate *E. coli* quantification.
➡️ The presence of fluorescence under UV light (366 nm), along with the pink color change, is the critical indicator confirming *E. coli* presence due to $\beta$-glucuronidase activity.
➡️ Proper aseptic technique during sample compositing (25g sample in 225 mL PSS) and media handling is crucial for reliable quantitative results.

📸 Video summarized with SummaryTube.com on Dec 01, 2025, 03:23 UTC