What is the medial significance of identifying a bacterial pathogen as G + or G-?

The relevance is the thickness of the cell wall.

Explanation:

Gram-positives have a more simple wall with a thick coat of peptidoglycan which will differ in the pathogenic action as well as the antibiotic effect. Gram-negatives, on the other hand, have a much complex wall with an outer and inner wall and a thin intermediate layer of peptidoglycan.