Gram-negative bacteria
Polyguanidines are another class of antimicrobial polymers containing nitrogen. This class of antimicrobial polymers is nontoxic and exhibits high water solubility. Polyguanidines display broad-spectrum antimicrobial activity and initially interact with microbes using electrostatic forces. Greater activity against gram-positive bacteria has been seen with polyguanidines than against gram-negative bacteria. The reason for the difference in activity is likened to the different structures of gram-positive and gram-negative bacteria. Gram-negative bacteria have a thinner peptidoglycan layer than gram-positive bacteria. In addition, gram-negative bacteria have an outer lipid membrane, which gram-positive bacteria do not. High molecular weight polymers are able to penetrate gram-positive bacteria.