Title : Lack of correlation between in vitro and in vivo assays when assessing colonization characteristics Of potentially probiotic bacteria
Abstract:
The survival and colonization stability of probiotic bacteria within the gastrointestinal tract of a host are important to ensure that the host receives constant benefits from the probiotic bacteria. Probiotics strains have generally been preselected based on a series of in vitro assays, such as tests of ability to adhere to cultured host cells, ability to withstand the low pH of the stomach and bile acids in the intestines. This study aimed to compare the performance of potential probiotics isolates in vitro and in vivo. Lactic acid bacteria were isolated from chicken guts and 67 strains from 24 species were examined in vitro, using resistance to acid and bile, and adherence to tissue culture cells assays. A chicken trial was carried out to assess their colonization and persistence characteristics in vivo. The birds were orally dosed with a mixture of LAB isolates. They were euthanised four weeks after the administration and caecal content was collected to analyse the presence of the input probiotic strains. The results showed that there was no clear correlation between in vivo colonization and persistence of isolates and their resistance to acid and bile, or adherence to tissue culture cells. Therefore the in vitro screening steps for probiotic strain selection should be considered carefully, as they may be a very poor indicator of a strains ability to survive passage through the harsh environment of the gastrointestinal tract and subsequent activity within the gut.
