Erythromycin antibiotic assay

Emmance at MSN.com Emmance at MSN.com
Mon Nov 17 23:52:57 EST 1997


Hi everyone,

I need help with a puzzling situation. Has anyone heard of analysts not
being able to perform 'Erythromycin antibiotic assay' for some unknown
reasons? I am currently facing with this dilemma. After training in
erythromycin assay, and after running the test four times successfully, I
started having problems with my correlation coefficient which has a
specification of 0.98 or better. My  correlation coefficient back in July
ranged between 0.80 to 0.97. I have taken all necessary measures to
control/eliminate errors. I have tarred the flasks and weighed out the
concentrations. I have changed the buffers, used new lot of organism
(Micrococcus luteus) and new media. I have placed the concentrations one
after the other, and moved them to a completely separate area after use
to avoid mix up. In addition, I have kept the 1.00- microgram
concentration to my left while the others are on my right. The problem
remains. The zone size for the 0.80 or the 1.25-microgram concentration
is equivalent to the 1.00. After several investigations, we concluded
that the problem was caused using cold buffer. I did an experiment using
cold and ambient buffers to prove this theory. The correlation
coefficient for the cold buffer was 0.973, and 0.998 for the warm buffer
(ambient). I figured then that my problem was resolved. I ran the test
one time successfully and then the same problem started happening again
(twice). The investigations conducted by my manager and myself just
cannot show what exactly I am doing wrong, altough we feel that the
problem is analyst related. Other analysts have been able to run the test
without any such problems.

My manager's conclusion was that he had heard of analysts not being able
to run the test for no factual/logical reasons. Altough I feel there is a
logical reason behind all this, I have no other choice but to accept this
conclusion until I can prove differently.

Please help!

thank you

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