Western blot alternatives
I think that enzyme-linked immunosorbent assay (or ELISA) is the best way to do so, given you have an antibody against the protein to coat the sample wells with... You could use mice to create polyclonal antibodies against your protein by injecting the protein and collecting the serum and purifying it...as long as there isn't similar proteins to the bacterial one in the sample you are testing for...but to diagnose an infection you could use something like q-PCR assuming you can get the bacterial DNA from the sample (you could use typical bacterial DNA extraction techniques).

For more on ELISA go here. Here is a good animation on ELISA:
http://highered.mheducation.com/sites/0072556781/student_view0/chapter33/animation_quiz_1.html