Method for Reducing the Population of at Least One Intestinal and/or Gastrointestinal Bacteria Species Comprising Bacteriophages, and Bacteriophages and the Use Thereof

A method for reducing the population of at least one intestinal and/or gastrointestinal species of bacteria, the method comprising the following steps:

• a) providing a biological sample containing bacteria of at least one intestinal and/or gastrointestinal species of bacteria, the intestinal and/or gastrointestinal species of bacteria directly or indirectly influencing a psychological, neurodegenerative and/or neurological illness and/or disorder of a host organism;
• and
• b) providing bacteriophages of at least one species of bacteriophages that are specific to the intestinal and/or gastrointestinal species of bacteria and that comprise at least one nucleic acid functionally associated with a promotor and/or a regulatory element, the nucleic acid being selected from the group comprising:
• i. a nucleic acid sequence coding for at least one antibacterial nucleic acid molecule;
• and
• ii. a nucleic acid sequence encoding a nucleic acid molecule that is identical to the nucleic acid molecule encoded by the nucleic acid sequences from i) by at least 50%;
• and
• iii. a nucleic acid sequence coding for at least one antibacterial polypeptide;
• and
• iv. a nucleic acid sequence encoding a polypeptide that is identical to the polypeptide encoded by the nucleic acid sequences from iii) by at least 50%;
• and
• v. a nucleic acid sequence for a fragment of a nucleic acid from i), ii), iii) or iv), the fragment encoding a nucleic acid molecule or a polypeptide;
• and
• c) contacting and incubating the biological sample with the bacteriophages, the incubation continuing until the population of the intestinal and/or gastrointestinal species of bacteria has been reduced by at least 70%.