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Gewählte Master / Diploma Thesis:

Christina Lippitsch (2011): Direct Detection of Viable Bacteria in Selected Dairy Products.
Master / Diploma Thesis - Institut für Lebensmittelwissenschaften, BOKU-Universität für Bodenkultur, pp 103. UB BOKU obvsg

Data Source: ZID Abstracts
Bacteria in food are often subjected to adverse conditions, which may induce certain stress responses like entering into the ‘viable but nonculturable state’ (VBNC). Entering the VBNC state has different morphological and physiological consequences. However, the possibility of resuscitation as a matter of providing promoted growth conditions is common for all VBNC cells. Previous studies suggested that bacteria in the VBNC state retain their pathogenicity and additionally can show an increased antibiotic resistance due to reduced metabolic activity. Although VBNC bacteria still show metabolic activity and thus can be considered as viable, they may not be detected by the use of most culture-based methods. This lack of detection leads to false negative or underestimated results. PCR based, non-cultural methods, which are often used as an alternative, do not discriminate between DNA from live or dead cells and therefore can lead to false positive or overestimated results. One possibility to exclude free DNA or DNA from dead bacteria during detection is the combination of ethidium monoazide (EMA) treatment and quantitative real-time polymerase chain reaction (qPCR). Along with universal primers targeting the 16S rRNA gene of prokaryotes, this combined method gives a good estimation of the total load of viable bacteria in samples. With regard to legal upper limits (e.g., pathogens) and lower limits (e.g., probiotics) the need for methods capable of differentiating between live and dead microorganisms becomes evident. Hence, the aim of this thesis was to develop a culture-independent method, which is able to estimate the real total viable count of bacteria in commercially available, probiotic dairy products.

Beurteilende(r): Kneifel Wolfgang
1.Mitwirkender: Domig Konrad

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