Cultivation Methods for Probiotic Enumeration

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The United States Pharmacopeia describes methods for quantifying the number of probiotics in a product. Choosing the right medium for a particular type of microorganism is extremely important. Testing the number of probiotics in medicinal products, dietary supplements, or foods for special medical purposes depends primarily on the composition of a given product (a preparation containing one, two, or more microorganisms) and its form. It is of great significance to study the quality of probiotic preparations by standardized methods.


The principle of this technique is that "when material containing bacteria is cultured, every living bacterium develops into a visible colony on nutrient agar". Thus, the number of colonies is the same as the number of organisms present in the sample. To obtain valid results, the original sample must be diluted so that the target bacteria grow between 30 and 300 colonies on average. Less than 30 colonies will make the account somewhat flawed, and more than 300 colonies will often lead to overlap and miscalculation.

Cultivation Methods at Creative Biolabs

Cultivation methods, such as plate counting, are the gold standard. Cell counts are usually performed by culture-dependent methods such as plate counts. These techniques reveal the number of living cells capable of replicating and generating colonies. The plate counting method is simple to operate, but it requires a long incubation time and the selection of an appropriate medium.

Evaluation of Cultivation Methods

Although plating directly on Petri dishes with agar medium is the most popular method, it has its limitations. The range of selective media available to identify and enumerate strains of probiotic interest is relatively limited. To overcome this, selective differential media have been developed, but the subjectivity of identification requires skilled personnel to obtain reliable results. In addition, they do not provide information about bacterial culture heterogeneity; that is, they do not detect cells in a viable but non-culturable (VBNC) state. It should also be noted that apart from the art and skill of the technician in cultivating the samples under the correct environmental conditions, a quick turnaround is not possible, as, at least 24-72 hours of growth in the incubator is necessary before colony counts can be performed.

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