04/08/2025
𝐖𝐡𝐚𝐭’𝐬 𝐑𝐞𝐚𝐥𝐥𝐲 𝐈𝐧𝐬𝐢𝐝𝐞 𝐚 𝐁𝐢𝐨𝐥𝐨𝐠𝐢𝐜𝐚𝐥 𝐈𝐧𝐝𝐢𝐜𝐚𝐭𝐨𝐫?
Every sterilization cycle must be trusted.
But how do we know for sure that the process actually worked?
Enter the Biological Indicator (BI) - and at the heart of every BI is a powerful solution called the Growth Medium.
This small component plays a big role in confirming the effectiveness of your sterilization.
What is Growth Medium?
Growth medium is a nutrient-rich solution designed to help bacterial spores grow - but only if they survived sterilization.
It’s stored in a sealed glass ampoule inside the BI.
If any viable spores are present after the cycle, the medium enables their growth and reveals the result through a color change.
What does it contain?
A standard growth medium is scientifically balanced with:
• Nutrients – Food source to support bacterial growth
• Water – Essential for all life processes
• pH Indicator – Detects acid production from bacterial growth
• Buffer – Maintains a stable pH during incubation
What does the color change mean?
• Starts as purple
• If spores survive and grow, acid is released → color turns yellow
• If spores are killed, no growth → color remains purple
This change tells you everything:
• Purple = Sterilization passed
• Yellow = Sterilization failed
What are the nutrients inside?
Inside the ampoule, you’ll typically find:
• Tryptic Soy Broth (TSB) – A protein-rich base
• Glucose – Energy source for bacterial metabolism
• Salts and Buffers – Maintain ideal conditions
• Water – Supports microbial life and reaction processes
If spores survive, they consume the nutrients and trigger a visible change.
If the sterilization is effective, no growth occurs, and the medium remains unchanged.
Think of it as:
Bacteria food + water + color detection system
It’s a reliable scientific tool that gives you visual proof, not assumptions.
Final Tip:
Always follow the manufacturer’s instructions for incubation time and temperature.Different BIs have different requirements.
If you’re training staff, auditing processes, or educating students, this knowledge is essential.