Mukhida Sahjid, Chavan Shazia, Pandya Vishal, Pandya Jaydev
Department of Microbiology, GMERS Medical College, Junagadh, Gujarat, India.
Department of Microbiology, Dr. D. Y. Patil Medical College, Hospital and Research Centre, Dr. D. Y. Patil Vidyapeeth, Pimpri, Pune, Maharashtra, India.
J Family Med Prim Care. 2025 May;14(5):1833-1842. doi: 10.4103/jfmpc.jfmpc_1626_24. Epub 2025 May 31.
To ensure quality control, microbiology laboratories should maintain a variety of bacterial and fungal strains. Once cultivated, these organisms can survive on the media as long as nutrients are available. Skim milk, a common freeze-drying protectant, can be used as a freezing solution for bacteria at low temperatures. The aim of this study was to prepare and validate a skim milk solution for bacterial strain storage.
A 10% skim milk solution was prepared and stored into 2-3 ml aliquots in sterile plastic vials. Subcultured organisms were inoculated into vials and stored at -20°C in a deep freezer. We checked the quality of the bacterial strains at regular intervals: 7 days, 15 days, 1 month, 2 months, and 3 months. Each time, a subculture was performed from the same vial to check the characteristics of the bacterial strain. All characteristics were recorded in the study Performa until the study's completion.
A total of 15 strains, including Gram-positive cocci, Gram-negative bacilli, and yeast strains, were included in the study. At all subculture times, organisms grew properly and exhibited similar colony characteristics. No changes were observed in the subculture from the first to the last inoculation of the bacterial organisms. Biochemical tests were conducted every time a subculture was performed to check for variations in properties, which were found to be consistent over time.
The skim milk solution offers an effective method for storing, maintaining, and reviving bacterial strains, for up to 3 months. This approach significantly reduces the labor-intensive work associated with regular subculture methods used for storing or reviving bacterial strains.
为确保质量控制，微生物实验室应保存多种细菌和真菌菌株。一旦培养出来，只要有营养物质，这些微生物就能在培养基上存活。脱脂乳是一种常见的冻干保护剂，可作为细菌低温冷冻保存液。本研究的目的是制备并验证用于保存菌株的脱脂乳溶液。
制备10%的脱脂乳溶液，并分装到2 - 3毫升无菌塑料小瓶中。将传代培养的微生物接种到小瓶中，存放在-20°C的低温冰箱中。我们定期（7天、15天、1个月、2个月和3个月）检查菌株质量。每次都从同一小瓶中进行传代培养，以检查菌株的特性。在研究完成前，所有特性都记录在研究表格中。
本研究共纳入15株菌株，包括革兰氏阳性球菌、革兰氏阴性杆菌和酵母菌株。在所有传代培养时间点，微生物生长良好，菌落特征相似。从首次接种到最后一次接种细菌，传代培养过程中未观察到变化。每次传代培养时都进行生化试验，以检查特性变化，发现其随时间保持一致。
脱脂乳溶液为保存、维持和复苏菌株提供了一种有效的方法，长达3个月。这种方法显著减少了与用于保存或复苏菌株的常规传代培养方法相关的劳动强度大的工作。
