Browsing by Subject "puhdistus- ja desinfiointiaineet"

Listeria monocytogenes is a gram-positive, non-sporeforming, rod-shaped bacterium, a human and animal pathogen and a food-borne pathogen/agent. Listeriosis, caused by L. monocytogenes, can be a serious disease and even cause death. L. monocytogenes is a major risk factor for the microbiological quality of foodstuffs, and a pathogen especially for those in risk groups. The aim of this study was to investigate sporadic and persistent strains of L. monocytogenes, isolated in a milk-production environment, and their growth in acidic and alkaline environments, as well as in environments containing the detergents Basix and Cidmax, and to investigate eventual differences between these strains. The features and occurrence of L. monocytogenes, its capability to resist stress and listeriosis are discussed in the literature part of this thesis. In this study it was found that bacteria were able to grow in the environments tested, in the concentrations used. No statistically significant differences between the strains were discovered. All investigated L. monocytogenes strains grew in pH 5.6, pH 9.0 and in liquids containing the detergents Cidmax and Basix. In acidic conditions, the majority of the strains grew similarly to reference strain EGD-e. Strain E3 started its exponential growth faster than the other strains. In acidic conditions strain D3 had the highest growth rate (30.06). The strains that grew the most weakly in acidic conditions were B3 and reference strain ATCC 19115. In alkaline conditions and in Cidmax-BHI liquid, the most of L. monocytogenes strains grow similarly to reference strain EGD-e. Strains E3 and D3 grew faster than other strains in alkaline conditions and Cidmax-BHI liquid and strains B3 and ATCC 19115 grew slower than the other strains. In Basix-BHI liquid, the strains of L. monocytogenes grew mainly similarly to each other, and these strains grew a little faster than reference strain EGD-e. Compared to the other strains, strain E3 grew the fastest and strains B3 and ATCC 19115 grew slower than the other strains. In this study, differences in stress tolerance between L. monocytogenes strains were found. In future, the results of this study may be utilized in genomic association research where geno- and phenotypes are compared to each other. This could produce new information on the development of stress tolerance of L. monocytogenes strains with different genomes and phenotypes.