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The object of the dissertation was the monitoring of the quantity of the yogurt culture microbes Lactobacillus delbrueckii subsp. bulgaricus and Streptococcus salivarius subsp. thermophilus in selected yogurts after the end of the mature process and the consideration of the observed values with the requirements of the legislation. The literary search mentions the fermented dairy products and their classification, the characterization of individual types of lactic fermentation microbes and also the pure milk cultures used for the production of soured dairy products are not left out. The experimental part deals with the evaluation of microbiological analysis and the acidity of selected yogurts according to the influence of the producer and the storage life. The observed results showed, that the legislative requirement for the quantity of live microbes has been kept not only during the prescribed best-before period, but also during the complete experiment, it means also on the 56th day of the storage.

The aim of the project is to investigate how a more viscous, gel like formulation can be made of BioGaia´s Prodentis Drops, which is a probiotic product for oral use. The two different strains of Lactobacillus reuteri that are used in the product, together called L. reuteri Prodentis, have been clinically proven to be effective in treatment of gingivitis and caries formation. The existing product is a highly liquid oil suspension that has been described as too runny and difficult to get into tooth pockets and between teeth. Therefore a gel formulation would be preferred. Pre-trials were excecuted to see what combinations and quantities of ingredients could work. Three different formulations using 3 %, 5 % and 7 % beeswax as thickening agent proceeded to another round of trials, as well as one formulation where the original oil was exchanged for hydrogenated rapeseed oil. In the beeswax formulations fumed silicon dioxide was being used as well. Three different analyses were executed, considering bacterial survival, viscosity and phase separation of gels. The bacterial survival proved to be acceptable in all samples even after 14 days of incubation in 37oC. The formulation with 7 % beeswax was the most viscous one, followed by 5 % beeswax, 3 % beeswax and the formulation with hydrogenated oil, respectively. Phase separation could be seen in the hydrogenated oil formulation already after seven days and even more so after 14 days. There were also signs of separation in the formulation with 3 % beeswax after 14 days. It was concluded that in further development of the Prodentis Drops it is recommendable to proceed with the 5 % beeswax formulation.

Campylobacter jejuni is the leading bacterial cause of gastrointestinal diarrheal disease in humans worldwide. This zoonotic pathogen has a complex epidemiology due to its presence in many different host organisms. The overall aim of this thesis was to explore the role of amoebae of the genus Acanthamoeba as an intermediate host and vector for survival and dissemination of C. jejuni. Earlier studies have shown that C. jejuni can enter, survive and replicate within Acanthamoebae spp. In this thesis, I have shown that C. jejuni actively invades Acanthamoeba polyphaga. Once inside, C. jejuni could survive within the amoebae by avoiding localization to degradative lysosomes. We also found that A. polyphaga could protect C. jejuni in acid environments with pH levels far below the range in which the bacterium normally survives. Furthermore, low pH triggered C. jejuni motility and invasion of A. polyphaga. In an applied study I found that A. polyphaga also could increase the survival of C. jejuni in milk and juice both at room temperature and at +4ºC, but not during heating to recommended pasteurization temperatures. In the last study we found that forty environmental C. jejuni isolates with low bacterial concentrations could be successfully enriched using the Acanthamoeba-Campylobacter coculture (ACC) method. Molecular genetic analysis using multilocus sequence typing (MLST) and sequencing of the flaA gene, showed no genetic changes during coculture. The results of this thesis have increased our knowledge on the mechanisms behind C. jejuni invasion and intracellular survival in amoebae of the genus Acanthamoeba. By protecting C. jejuni from acid environments, Acanthamoebae could serve as important reservoirs for C. jejuni e.g. during acid sanitation of chicken stables and possibly as vectors during passage through the stomach of host animals. Furthermore, Acanthamoeba spp. could serve as a vehicle and reservoir introducing and protecting C. jejuni in beverages such as milk and juice. Validation of the ACC method suggests that it is robust and could be used even in outbreak investigations where genetic fingerprints are compared between isolates. In conclusion, Acanthamoeba spp. are good candidates for being natural hosts and vectors of C. jejuni.