Benzalkonium chloride (alkyl dimethyl benzyl ammonium chloride) is an organic compound that is used as an antiseptic.

Benzalkonium chloride is a mixture of alkylbenzyl dimethylammonium chlorides of various alkyl chain lengths. This product is a nitrogenous cationic surface-acting agent belonging to the quaternary ammonium group. The greatest bactericidal activity is associated with the C12-C14 alkyl derivatives.

It is one of the safest synthetic biocides known, and has a long history of efficacious use. Applications are extremely wide ranging, from disinfectant formulations as hand and face washes, mouthwashes, spermicidal creams, and in various other cleaners and sanitizers to microbial corrosion inhibition in the oilfield sector.

Benzalkonium chloride solutions are rapidly acting anti-infective agents with a moderately long duration of action. They are active against bacteria and some viruses, fungi, and protozoa that commonly thrive on human skin and nails. Bacterial spores are considered to be resistant. Solutions are bacteriostatic or bactericidal according to their concentration. Gram-positive bacteria are generally more susceptible than gram-negative.

The mechanism of bactericidal/microbicidal action of benzalkonium chloride is thought to be due to disruption of intermolecular interactions. This can cause dissociation of the cells’ membrane of microorganisms, which induces leakage of cell’s contents. Other biomolecular complexes within the bacterial cell can also undergo dissociation. Cell enzymes, which finely control a plethora of respiratory and metabolic cellular activities, are particularly susceptible to deactivation.

Antimicrobial activity of Benzalkonium chloride is not greatly affected by pH, but increases substantially at higher temperatures and prolonged exposure times. Formulation with Benzalkonium may be inactivated by certain organic compounds, including soap, and must not be mixed with anionic surfactants. Hard water salts can also reduce biocidal activity. Although newer formulations are more resistant to deactivation, as with any disinfectant, it is recommended that surfaces are rinsed well before disinfection.

Glossary:

• Biocide is a chemical substance capable of killing different forms of living organisms used in fields such as medicine, agriculture, forestry, and mosquito control.

• Disinfectants are antimicrobial agents that are applied to non-living objects to destroy microorganisms, the process of which is known as disinfection. Disinfectants should generally be distinguished from antibiotics that destroy microorganisms within the body, and from antiseptics, which destroy microorganisms on living tissue. Sanitisers are high level disinfectants that kill over 99.9% of a target microorganism in applicable situations. Not all disinfectants and sanitisers can sterilise (the complete elimination of all microorganisms), and those that can depend entirely on their mode of application. Bacterial endospores are most resistant to disinfectants, however some viruses and bacteria also posess some tolerance.

• Bacteriostatic and bactericidal. Bacteriocidal agents kill bacteria; bacteriostatic agents only slow their growth or reproduction. Bacteriostatic agents inhibit growth and reproduction of bacteria without killing them by: interfering with bacteria protein production, interfering with bacteria DNA production or interfering with bacteria cellular metabolism. Bactericidal agent is a substance that kills bacteria. Bactericides are disinfectants, antiseptics or antibiotics. Bacteriostatic agents. High concentrations of most bacteriostatic agents are also bacteriocidal, whereas low concentrations of bacteriocidal agents are only bacteriostatic.

• Bacteria (singular: bacterium) are microscopic, unicellular organisms. Bacteria are the causative agent of many infectious diseases.

  Gram-positive bacteria are classified as bacteria that retain a crystal violet dye during the Gram stain process. Gram-positive bacteria will appear blue or violet under a microscope, whereas Gram-negative bacteria will appear red or pink. The difference in classification is largely based on a difference in the bacteria's cell wall structure. Both Gram-positive and Gram-negative bacteria may have a membrane called an S-layer. In Gram-negative bacteria, the S-layer is directly attached to the outer membrane. In Gram-positive bacteria, the S-layer is attached to the peptidoglycan layer. Unique to Gram-positive bacteria is the presence of teichoic acids in the cell wall. Some particular teichoic acids, lipoteichoic acids, have a lipid component and can assist in anchoring peptidoglycan, as the lipid component is embedded in the membrane. One of the several unique characteristics of Gram-negative bacteria is the outer membrane. This outer membrane is responsible for protecting the bacteria from several antibiotics, dyes, and detergents which would normally damage the inner membrane or cell wall (peptidoglycan). The outer membrane provides these bacteria with resistance to lysozyme and penicillin. Fortunately, alternative medicinal treatments have been developed to combat the protective outer membrane of some pathogenic Gram-negative organisms.

  The Gram-positive forms include many well-known genera such as Bacillus, Listeria, Staphylococcus, Streptococcus, Enterococcus, and Clostridium. It has also been expanded to include the Mollicutes, bacteria like Mycoplasma that lack cell walls and so cannot be stained by Gram, but are derived from such forms. The actinobacteria are another major group of Gram-positive bacteria; the Deinococcus-Thermus bacteria also have Gram-positive stains, although they are structurally similar to Gram-negative bacteria.

  Many species of Gram-negative bacteria are pathogenic, meaning they can cause disease in a host organism. This pathogenic capability is usually associated with certain components of Gram-negative cell walls, in particular the lipopolysaccharide (also known as LPS or endotoxin) layer.

  The proteobacteria are a major group of Gram-negative bacteria, including Escherichia coli, Salmonella, and other Enterobacteriaceae, Pseudomonas, Moraxella, Helicobacter, Stenotrophomonas, Bdellovibrio, acetic acid bacteria, Legionella and many others. Other notable groups of Gram-negative bacteria include the cyanobacteria, spirochaetes, green sulfur and green non-sulfur bacteria. Medically relevant Gram-negative cocci include three organisms, which cause a sexually transmitted disease (Neisseria gonorrhoeae), a meningitis (Neisseria meningitidis), and respiratory symptoms (Moraxella catarrhalis). Medically relevant Gram-negative bacilli include a multitude of species. Some of them primarily cause respiratory problems (Hemophilus influenzae, Klebsiella pneumoniae, Legionella pneumophila, Pseudomonas aeruginosa), primarily urinary problems (Escherichia coli, Proteus mirabilis, Enterobacter cloacae, Serratia marcescens), and primarily gastrointestinal problems (Helicobacter pylori, Salmonella enteritidis, Salmonella typhi). Nosocomial gram negative bacteria include Acinetobacter baumanii, which cause bacteremia, secondary meningitis, and ventilator-associated pneumonia in intensive care units of hospital establishments. Bacterial species Pseudomonas and Staphylococcus are known cause of nail and skin infections.

• Virus (Latin, poison) is a microscopic particle that can infect the cells of a biological organism. At the most basic level, viruses consist of genetic material contained within a protective protein coat called a capsid; the existence of both genetic material and protein distinguishes them from other virus-like particles such as prions and viroids. They infect a wide variety of organisms: both eukaryotes (animals, fungi and plants) and prokaryotes (bacteria). A virus that infects bacteria is known as a bacteriophage, often shortened to phage.

• Fungi (singular fungus) are a kingdom of eukaryotic organisms. They are heterotrophic and digest their food externally, absorbing nutrient molecules into their cells. Yeasts, molds, and mushrooms are examples of fungi. Fungi (Trichophyton, Microsporum and Epidermophyton), molds (Scytalidium, Scopulariopsis and Aspergillus) and yeasts (Candida) cause the majority of the nail infections cases worldwide.

• Protozoa (in Greek proto = first and zoa = animals) are single-celled eukaryotes (organisms whose cells have nuclei) that commonly show characteristics usually associated with animals, most notably mobility and heterotrophy. They are often grouped in the kingdom Protista together with the plant-like algae and fungus-like water molds and slime molds. In some newer schemes, however, most algae are classified in the kingdoms Plantae and Chromista, and in such cases the remaining forms may be classified as a kingdom Protozoa. The name is misleading, since they are not animals.

• Spore is a reproductive structure that is adapted for dispersion and surviving for extended periods of time in unfavorable conditions. Spores form part of the life cycles of many plants, algae, fungi and some protozoans. Spores are usually haploid and unicellular and are produced by meiosis in the sporophyte. Once conditions are favorable, the spore can develop into a new organism using mitotic division, producing a multicellular gametophyte, which will eventually go on to produce gametes. Two gametes fuse to create a new sporophyte. This cycle is known as alternation of generations. Haploid spores produced by mitosis (known as mitospores) are used by many fungi for asexual reproduction.

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