Doctors, what is the difference between gram positive cocci & gram negative bacilli?

Gram stain. The gram stain has been used for a long time to classify bacteria according to the chemistry of their cell walls (and hence whether they are gram positive or negative.) Cell shape and growth characteristic are also useful in grouping bacteria until more full speciation information becomes available. The gram stain is fast, reasonably reproducible by trained personnel and the groupings useful 4 rx.