A few Gram-positive bacteria are intrinsically resistant to vancomycin: ''[[Leuconostoc]]'' and ''[[Pediococcus]]'' species, but these organisms rarely cause diseases in humans [REF].
One mechanism of resistance to vancomycin involves the alteration to the terminal amino acid residues of the NAM/NAG-peptide subunits, under normal conditions, <small>D</small>-alanyl-<small>D</small>-alanine, to which vancomycin binds.