A Disinfectant is a chemical agent that is used to reduce the number of viable microorganisms on pharmaceutical surfaces to an acceptable level. Disinfectants have a variety of properties that include spectrum of activity, mode of action, and effectiveness. Some are bacteriostatic, where the ability of the bacterial population to reproduce is halted. In this case, the disinfectant can cause selective and reversible changes to microbial cells by interacting with nucleic acids and inhibiting enzymes, or permeating into the cell wall. Once the disinfectant is removed from contact with bacterial cells, the surviving bacterial population can potentially grow. Other disinfectants are bactericidal in that they destroy bacterial cells and cause irreversible damage through different mechanisms that include structural damage to the cell, cell lysis, and autolysis, resulting in leakage or coagulation of cytoplasm. The destruction of bacterial and fungal spores is a property which a given disinfectant may or may not possess. This type of chemical agent is called a sporicide. A chemical agent does not have to be sporicidal in order to be classified as a ‘disinfectant’ or as a ‘biocide’. The bacteriostatic, bactericidal and sporicidal properties of a disinfectant is influenced by many variables.