problems with immunolabeling

[pz5]

Greetings,
        I am currently having difficulties with poor labeling on S. aureus
and S. epi cells.  The antibodies have been tested by ELISA and the titers
are very high 1:50,000.  The cells are embedded in LR White and ultrathin
sectioned.  After labeling the cells are viewed by electron microscopy.  I
have tried several protocols, including using skim milk and BSA to block with
at different concentrations. Additionally the PAG binds nonspecifically to S.
aureus and thus IgG goat anti-mouse or anti-rabbit must be used as the
secondary antibody. I have tried these for a variety of concentrations and
times. The primary antibody has been used at a concentration of 1:20, in which
there is no labeling, to 1:5,  in which the labeling is small.  Thanks for your
help.  If you need additional info please e-mail.