Phage typing of
with a new
Pia Rasmussen, Mette Dines Cantor, and
Chr. Hansen A/S,
, Bøge Allé 10
12, 2970 Hørsholm, Den
Infection with bacteriophages
still a major pro
blem during dairy fermentations making the
development of new starter cultures belonging to different lytic groups a challenge for the
To be able to test a high number of lactococcal strains we have developed a high throughput
phage typing method based on a
microtiter plate system.
romo cresol purple and
romo cresol green
as pH indicators.
of the indicator added milk
in the microtiter plates was estimated using image analysis of digital picture recorded by flat
The phage typing
was made by pipetting 44 phages from mainly different lytic groups
into the micr
s with the help of a liquid handling robot.
strains from Chr. Hansen
culture collection were added (two strains per plate)
with the automised system.
of the strains were attacked by one or
more of the test phage
leaving 482 (86%) strains
The system delivers in parallel acidification data which can be used to preselect strains with a
certain acidification rate.
Subtracting slow and medium acidifying strains from the non
, 72 (13%)
strains remained with good acidification properties in
addition to the phage resistance.
The poster discusses also the distribution of the
sensitivity of the single test strains regarding
the three main phage species c2,
, and P335.