Microbial Limits Testing is Used to determine whether a non-sterile pharmaceutical product complies with an established specification for microbial quality. This is an important series of Tests designed to limit the likelihood of any adverse incident occurring as a result of a high degree of microorganisms being present in a non-sterile item. By placing limits on the numbers of bacteria present in the product under test you inherently decrease the probability of this occurring. The harmonised test methods and specifications used to ensure the microbial quality of pharmaceuticals are described in the British Pharmacopoeia, European Pharmacopoeia, Japanese Pharmacopoeia and US Pharmacopoeia.
The bioburden testing described in these four pharmacopoeias is performed in two parts and is intended to perform the qualitative and quantitative determinations of particular viable microorganisms within pharmaceutical products. These parts consist of the Microbial Enumeration Test which is a quantitative enumeration of mesophilic bacteria and fungi yeasts, moulds that grow under aerobic conditions and the Tests for Specified Microorganisms which test for the presence of Escherichia coli, Salmonella species, Pseudomonas aeruginosa, Staphylococcus aureus, Candida albicans, Clostridium species, and Bile-tolerant Gram-negative bacteria.
Once the microorganisms Have been extracted into solution, there are a couple of methods of culturing the microbes that could be used. The most common technique is membrane filter in which the solution of germs is filtered through a sterile filter paper and the filter paper is moved on a suitable agar plate and incubate. Another method is pouring plate method by which a small percentage 1 mL of the extract is mixed with molten agar medium and incubate under appropriate conditions. The alternative of growth media and incubation conditions will be based on the sort of germs to be enumerated. For aerobic bioburden, both bacteria and fungi molds and yeast colonies are enumerated while for anaerobic bioburden, anaerobic bacteria colony counts are determined. The media and incubation condition and period are outlined below.
