Germicidal quaternaries (Multi-San, Medi Quat 4 and Sanitrol MB) carry a positive charge. Surfaces of microorganisms (algae, bacteria, fungi, and viruses) carry a negative charge. When a germicidal quaternary is applied, the positively-charged quaternary attaches itself to the negative sites on the organism’s cell surface. This results in the disruption of the organism’s cell surface which eventually kills the organism.
A sterilant kills all bacteria and spores on environmental surfaces. Quaternaries are not sterilants since they are not effective against spores.