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Yu-Ting Wang, Division of Research and Analysis, Food and Drug Administration, Ministry of Health and Welfare, Taipei, Taiwan
Jyue-Wei Chuang, Division of Research and Analysis, Food and Drug Administration, Ministry of Health and Welfare, Taipei, Taiwan
Ming-Sian Wu, Division of Research and Analysis, Food and Drug Administration, Ministry of Health and Welfare, Taipei, Taiwan
Min-Cheng Wang, Division of Research and Analysis, Food and Drug Administration, Ministry of Health and Welfare, Taipei, Taiwan
Yu-Cheng Yang, Division of Research and Analysis, Food and Drug Administration, Ministry of Health and Welfare, Taipei, Taiwan
Jun-Jie Yang, Division of Research and Analysis, Food and Drug Administration, Ministry of Health and Welfare, Taipei, Taiwan
Shih-Ting Chiou, Division of Research and Analysis, Food and Drug Administration, Ministry of Health and Welfare, Taipei, Taiwan
Chun-Hsien Li, Division of Research and Analysis, Food and Drug Administration, Ministry of Health and Welfare, Taipei, Taiwan
Che-Yang Lin, Division of Research and Analysis, Food and Drug Administration, Ministry of Health and Welfare, Taipei, Taiwan
Shou-Chieh Huang, Division of Research and Analysis, Food and Drug Administration, Ministry of Health and Welfare, Taipei, Taiwan
Su-Hsiang Tseng, Division of Research and Analysis, Food and Drug Administration, Ministry of Health and Welfare, Taipei, Taiwan
Der-Yuan Wang, Division of Research and Analysis, Food and Drug Administration, Ministry of Health and Welfare, Taipei, TaiwanFollow

Keywords

D-Gluconic acid, Oxacillin, Peptone from soymeal, 2, 3, 5-Triphenyltetrazolium chloride

Abstract

Limosilactobacillus reuteri is a probiotic bacterium known for its numerous beneficial effects on human health and is commonly utilized in various dietary supplements. Previously, we encountered difficulties in isolating L. reuteri from retail dietary supplements containing complex probiotic compositions by using non-selective media such as de Man, Rogosa, and Sharpe (MRS) agar. Our findings reveal that MRS agar using D-gluconic acid as the carbon source and peptone from soymeal as the nitrogen source provid a growth advantage for L. reuteri. Furthermore, all the tested L. reuteri strains exhibit higher resistance to oxacillin compared to non-L. reuteri strains and the recovery of L. reuteri is significantly higher than that of non-L. reuteri strains on modified MRS agar (MRS-GSOT agar) supplemented with either 4 or 10 μg/ mL oxacillin. Results of spiking tests indicate that MRS-GSOT agar with 10 μg/mL oxacillin could selectively inhibit the growth of species other than L. reuteri in single culture or mixed bacterial broth within food matrices. However, the recovery of L. reuteri is relatively low when subjected to the spiking tests of various ratios of the non- L. reuteri. Testing results of 15 retail dietary supplements also showed that MRS-GSOT agar could efficiently isolate L. reuteri from retail dietary supplements with complex compositions of probiotic bacteria. In addition, we observe that L. reuteri exhibits two different colony morphologies on MRS-GSOT agar with 10 μg/mL oxacillin, yet they shared a common feature: a noticeable metallic (golden) sheen on the colony surface when the plate is slightly tilted, which can be used to distinguish the them from those of non-L. reuteri species, such as Lactiplantibacillus plantarum subsp. plantarum, Levilactobacillus brevis, and Bifidobacterium longum subsp. longum. In conclusion, we have developed MRS-GSOT agar containing D-gluconic acid, peptone from soymeal, oxacillin, and 2,3,5-triphenyltetrazolium chloride for efficient isolation of L. reuteri from dietary supplements.

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Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License
This work is licensed under a Creative Commons Attribution-Noncommercial-No Derivative Works 4.0 License.

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