Microbial contamination and spoilage are assessed by the following methods:

Physical and Chemical Changes: Microbial contamination and spoilage in various pharmaceutical formulations can be identified by the physical and chemical changes (like change in viscosity, pH, emulsion stability, and loss of surface activity) occurring in it. Amount of oxygen consumed by the available product indicates the degree of oxidative attack and microbial growth.

Sterility Test: It is essential that materials subjected for sterility testing should not be contaminated by the operator or the environment during the testing process. Thus, it is essential to conduct a sterility test by competent and experienced personnel in an adequately clean room with laminar flow cabinet facilities. Sterile preparations (like injectables and ophthalmic preparations) should undergo sterility testing.

Assessment of Viable Microorganisms in Non-Sterile Products: Viable microorganisms in non-sterile products are tested for detection of pathogens and total viable counts.

Estimation of Pyrogens: An agent causing rise in temperature when injected into a patient is known as pyrogen. The lipopolysaccharides and lipoproteins which are chief constituents of the cell wall of gram-negative bacteria are called endotoxins.

These endotoxins are commonly known as pyrogens. Pyrogens are detected by two main procedures:

In BP pyrogen test, pyrogens are injected in laboratory rabbits and their body temperature is monitored for a specific period of time.

In Limulus Amoebocyte Lysate test (LAL), the pyrogen-containing sample causes gel formation in the lysis product of amoebocyte cells of the giant horseshoe carb (Limulus polyphemus).