Sterility refers to the complete absence of viable microorganisms, including bacteria, fungi, and spores, on a product or in a substance.
In the pharmaceutical industry, sterility is critical for products like injectables, ophthalmic solutions, and surgical instruments to prevent infections and ensure patient safety.
Sterility testing is a key process in quality control to confirm that a product meets the required sterility standards before it is released for use.
๐๐จ๐ฆ๐ฆ๐จ๐ง ๐๐ญ๐๐ซ๐ข๐ฅ๐ข๐ณ๐๐ญ๐ข๐จ๐ง ๐๐๐ญ๐ก๐จ๐๐ฌ
To eliminate microbial life, various physical and chemical processes are utilized:
- ๐๐๐๐ญ: The most common method. Autoclaving uses moist heat and pressure (typically 121ยฐC for 15โ20 minutes). Dry heat ovens are used for heat-stable powders or glassware.
- ๐ ๐ข๐ฅ๐ญ๐ซ๐๐ญ๐ข๐จ๐ง: Used for heat-sensitive liquids. Microorganisms are physically trapped using membrane filters with microscopic pore sizes (usually 0.22 ฮผm).
- ๐๐ซ๐ซ๐๐๐ข๐๐ญ๐ข๐จ๐ง: Uses gamma rays or electron beams to destroy microbial DNA without generating high heat.
- ๐๐ก๐๐ฆ๐ข๐๐๐ฅ ๐๐ญ๐๐ซ๐ข๐ฅ๐ข๐ณ๐๐ญ๐ข๐จ๐ง:Uses gases like ethylene oxide or hydrogen peroxide for delicate medical instruments that could be damaged by heat or moisture.
๐๐ญ๐๐ซ๐ข๐ฅ๐ข๐ญ๐ฒ ๐๐๐ฌ๐ญ๐ข๐ง๐
Because it is impossible to test every single item in a batch without destroying it, laboratories rely on sample testing to ensure compliance. Common testing techniques include:
- ๐๐๐ฆ๐๐ซ๐๐ง๐ ๐ ๐ข๐ฅ๐ญ๐ซ๐๐ญ๐ข๐จ๐ง: Passing a liquid sample through a sterile filter and placing the filter into a growth medium.
- ๐๐ข๐ซ๐๐๐ญ ๐๐ง๐จ๐๐ฎ๐ฅ๐๐ญ๐ข๐จ๐ง: Placing small portions of the product directly into nutrient broths, such as Fluid Thioglycollate Medium and Soybean-Casein Digest Medium.
Samples are typically incubated for up to 14 days. If the broth remains clear, the batch passes; if it becomes cloudy (turbid), it indicates microbial growth and batch failure.
๐๐ญ๐๐ซ๐ข๐ฅ๐ข๐ญ๐ฒ ๐๐ฌ๐ฌ๐ฎ๐ซ๐๐ง๐๐ ๐๐๐ฏ๐๐ฅ (๐๐๐)
In practice, achieving absolute “zero” microorganisms is nearly impossible to prove mathematically and is often too harsh for active ingredients. Therefore, microbiology and pharmaceutical industries use the Sterility Assurance Level (SAL) to define sterility practically.
*An item is considered sterile if the SAL is โค 10โปโถ.
*This means there is less than a 1-in-1-million probability of a single viable microorganism surviving in or on the product
