A Rapid Microcolony Analysis for the Count of Viable Bacteria in Solid Commercial Products

• Published in: Chōnai saikingaku zasshi Vol. 28; no. 4; pp. 165 - 172
• Main Authors: MAEDA, Ayako, OZAKI, Toru, SHIMAKAWA, Masaki, OHNO, Hiroshi, YAMAMURA, Hideki
• Format: Journal Article
• Language: Japanese; English
• Published: Tokyo The Intestinal Microbiology Society 01.01.2014; Japan Science and Technology Agency
• Subjects: Bacteria; Bifidobacterium; Microcolony analysis; Plate count analysis; Rapid detection; Solid commercial products; Viable bacteria number
• DOI: 10.11209/jim.28.165
• ISSN: 1343-0882

It takes one to several days to determine the number of viable microbial cells by plate count analysis. Microcolony analysis is based on plate count analysis, and is used to detect the early stage of colony formation by staining with a fluorescent dye and observation under a fluorescence microscope. Using this method, it is possible to measure the number of bacteria with growth ability in a short time. As this analysis collects bacteria by filtration, it is used to measure the number of viable bacteria in liquid samples rather than solid samples containing insoluble materials. We usually use the plate count analysis to count the number of viable bacteria in solid commercial products such as pharmaceuticals and quasi drugs. However, a more rapid, accurate and simple technique is required. In this study, we investigated the feasibility of microcolony analysis for the quantification of viable bacteria in solid products, and obtained the following results. 1. SYTO®9 is an optical fluorescent dye which can be used to prevent the staining of nonspecific insoluble excipients in products. 2. When the samples were centrifuged for 5 min at 150×g, the insoluble excipients were mostly removed. Therefore, it became possible to prevent the collapse of the shape of microcolonies. 3. The number of viable bacteria was accurately estimated when the microcolonies were counted in over 10 microscopic fields with 5×objective. Under these measurement conditions, we demonstrated that microcolony analysis can determine more rapidly and accurately than plate count analysis the number of viable bacteria in a Bifidobacterium solid product as well as several commercial products. In conclusion, we have demonstrated that modified microcolony analysis can be used as an alternative analysis to plate count analysis.