I am part of an IOE referance laboratory for salmonellosis and have been
serotyping for a number of years now. We have expanded our testing to
include phagetyping of S.enteriditis and more recently S.hadar and
S.typhimurium. The smaller typing schemes such as S.enteriditis (13
phages) and S.hadar (9 phages) can be easily done dropping one phage at a
time onto a bacterial lawn. The S.typhimurium scheme is a another matter
however! There are a minimum of 30 phages (maybe 34 in some cases) which
have to be dropped!
We have tried out various devices such as the Cathra replicating system
which uses metal pins that dip into a multi-well reservoir. Unfortunatly,
the pins must be flamed before applying phage to the next plate which
heats up the pins considerably by the end of the application session.
Also the pins touch the plate and disturbs the bacterial lawn which
causes difficulties interpreting negative reactions. This last problem
also arises using a bacterial loop device we aquired for big bucks.
I have seen a device in which a series of syringes are placed in a press
which slowly presses a drop out which hangs on the tip of the needle,
then the plate is gently lifted to touch the drops. This type of device
would be perfect but no one knows where this machine came from! A
thirty-six channel pipettor (arranged in a six by six pattern spaced
slightly wider than a 96 well plate so the drops don't spread into one
another on the plate) would be nice.
If anyone has any ideas, help me, I'm obsessed with this problem!
