How do scientists ensure that autoclaved materials were actually sterilized?

• A. By measuring the temperature of the autoclave chamber after the cycle
• B. By using biological indicators such as Bacillus spores to confirm the destruction of all microorganisms
• C. By visually inspecting the materials for any signs of contamination
• D. By checking for changes in the color of the autoclave tape only

Answer: (B)

Verified step by step guidance

1. Understand that sterilization is the complete destruction of all microorganisms, including resistant spores, which is critical in microbiology to prevent contamination.
2. Recognize that simply measuring the temperature of the autoclave chamber or visually inspecting materials is not sufficient to confirm sterilization because these methods do not directly verify microbial death.
3. Learn that biological indicators contain highly resistant bacterial spores, such as those from Bacillus species, which serve as a test to confirm sterilization effectiveness.
4. Know that after an autoclave cycle, these biological indicators are incubated to check for any surviving spores; no growth indicates successful sterilization.
5. Understand that chemical indicators like autoclave tape only show that certain conditions (like temperature) were met, but do not confirm microbial death, so biological indicators provide the most reliable confirmation.