Simultaneous Occurrence of Yeast (Mold) and Bacteria


Hello, I was working on a sample (flour) and I observed the PCA (Plate Count Agar) plates to be 0 and a high number of yeasts on the SDA (Sabouraud Dextrose Agar) plates. Is this microbiologically possible, to have yeast and mold present in a sample, while there is an absence of bacteria

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Anonymous 2023-02-22T09:50:56+00:00 1 Answer 17 views 0

Answer ( 1 )


    Yes, it is microbiologically possible to have a sample that contains both yeasts and molds, while at the same time being devoid of bacteria. The absence of bacterial growth on the Plate Count Agar (PCA) plates suggests that the sample does not contain viable bacteria at the time of testing, while the presence of yeasts on the Sabouraud Dextrose Agar (SDA) plates indicates that viable yeast cells are present in the sample.

    Yeast and molds are two different types of fungi, and they can coexist in the same environment. While both yeasts and molds are capable of degrading carbohydrates and other nutrients, yeasts are generally better adapted to survive in low-moisture environments, such as the dry conditions found in flour. In contrast, molds thrive in higher-moisture environments and can produce visible spores that can be easily detected on agar plates.

    It’s worth noting that while the absence of bacterial growth on PCA plates may be indicative of a lack of viable bacteria in the sample, it’s possible that the bacteria in the sample are present in very low numbers, or that they require different nutrients or environmental conditions to grow compared to the bacteria that are typically detected using PCA. Therefore, it’s important to use multiple culture media to detect a broad range of microorganisms in a sample.

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