Abstract: The present invention relates to a kit suitable for detection and quantification of phage DNA from a lactic acid bacteria infecting phage in a dairy sample. The invention provides a quantitative polymerase chain reaction (qPCR) kit for detection and quantification of phage DNA to from a lactic acid bacteria infecting phage in a dairy sample, said kit comprising a first primer pair and wherein said first primer pair has a robustness of a delta Cq lower than 1.0 cycle when tested in a temperature range of 55.0-70.0, preferably 55.0-68.0, more preferably 58.6-65.6 degrees Celsius and wherein said first primer pair is directed to a lactic acid bacteria infecting phage which is a lactococcal phage from the subgroup 9362, c2 or P335 or a streptococcal phage from the subgroup pac.

Abstract: The present invention relates to a method for obtaining a bacteriophage insensitive mutant of a lactic acid bacterium parent strain suitable for food and feed fermentation. Further, the present invention relates to a method for the construction of a bacteriophage insensitive lactic acid bacterium whereby the phage resistance is conferred by a mechanism other than CRISPR. A preferred lactic acid bacterium is Streptococcus thermophilus.

Abstract: The present invention provides a method for the construction of a bacteriophage-insensitive mutant of a Streptococcus thermophilus parent strain whereby the bacteriophage insensitivity is not based on the CRISPR resistance mechanism but based on another mechanism. The method provides a protocol by which this can be achieved by inactivating one or more of the CRISPR systems present in a given strain. The invention also provides the bacteriophage-insensitive mutants as well as their use in a process for making a dairy product.

Abstract: The present invention provides a method for the construction of a bacteriophage-insensitive mutant of a Streptococcus thermophilus parent strain whereby the bacteriophage insensitivity is not based on the CRISPR resistance mechanism but based on another mechanism. The method provides a protocol by which this can be achieved by inactivating one or more of the CRISPR systems present in a given strain. The invention also provides the bacteriophage-insensitive mutants as well as their use in a process for making a dairy product.