Sterility Test – When the Product Renders the Medium Turbid: Root Cause, Investigation, and Preventive Actions
Sterility testing is one of the most critical microbiological quality control procedures in the pharmaceutical industry. It ensures that sterile products—such as injectables, ophthalmic solutions, and biological preparations—are free from viable microorganisms. However, sometimes during testing, the sterility test medium becomes turbid even in the absence of microbial contamination. This condition, often described as “product renders the medium turbid” , can lead to false-positive results and unnecessary investigations if not correctly identified and justified. Understanding Turbidity in Sterility Test Medium The sterility test medium—such as Fluid Thioglycollate Medium (FTM) and Soybean Casein Digest Medium (SCDM) —is normally clear and transparent before incubation. Turbidity in the medium is typically interpreted as microbial growth, which signifies contamination. However, certain product formulations can cause the medium to appear turbid even when sterile, due to c...
