Active substances in biocidal products – Part II – Peroxides, biguanides

Peroxides

Hydrogen peroxide (H₂O₂) was first discovered in 1818 by the French chemist Louis Jacques Thénard, who obtained it by treating barium peroxide with nitric acid. This method was used from the end of the 19th century to the middle of the 20th century. Pure hydrogen peroxide was first obtained in 1894 (by vacuum distillation) by Richard Wolffenstein, nearly 80 years after its discovery.

It is used as a disinfectant, sterilant, and antiseptic. It is not sold in its pure state, being produced in the form of a 35–70% aqueous solution. Under normal conditions, hydrogen peroxide is stable when stored properly (e.g., in dark containers). Decomposition or loss of potency in small containers is less than 2% per year at ambient temperatures. However, stabilizers are used to prevent or slow down its decomposition: mineral acids to keep the solution acidic (maximum stability is at a pH of 3.5–4.5), complexing or chelating agents to inhibit metal-catalyzed decomposition, colloidal agents to neutralize small amounts of colloidal catalysts or to absorb impurities.

It acts on a broad microbial spectrum, having greater efficacy against gram-positive bacteria. A bactericidal and virucidal action has been demonstrated within one minute, and a mycobactericidal and fungicidal action within 5 minutes.

Hydrogen peroxide is used for the disinfection of hard surfaces, semi-critical and non-critical instruments, including flexible endoscopes, biprism tonometers, ventilators, fabrics, and even soft contact lenses (e.g., 3% for 2-3 hours).

Mechanism of action: it acts as an oxidant by producing hydroxyl free radicals that attack the lipids, proteins, and DNA of microbial agents.

Peracetic acid or peroxiacetic acid is considered a more powerful biocide than hydrogen peroxide, being sporicidal, bactericidal, virucidal, and fungicidal at low concentrations (0.3%). Peracetic acid inactivates gram-positive and gram-negative bacteria, fungi, and yeasts in ≤5 minutes at <100 ppm. In the presence of organic matter, 200-500 ppm are required. For viruses, the dosage range is wide (12–2250 ppm). In combination with hydrogen peroxide, it exhibits strong bactericidal activity (1.5 hours against MRSA and carbapenem-resistant E. coli). Peracetic acid 0.08% in combination with hydrogen peroxide 1.0% inactivates glutaraldehyde-resistant mycobacteria.

As it is not decomposed by peroxidases, unlike H₂O₂, it remains active in the presence of organic matter and is sporicidal even at low temperatures. It decomposes into oxygen, acetic acid, and hydrogen peroxide (acetic acid and hydrogen peroxide are further decomposed into water, carbon dioxide, and oxygen).

The stability of peracetic acid depends on the formulation. It is considered unstable, especially when diluted: a 1% solution loses half of its efficacy through hydrolysis in 6 days, while 40% peracetic acid loses 1%-2% of active ingredient per month.

It can corrode copper, brass, bronze, plain steel, and galvanized iron, but these effects can be reduced by adding additives and by modifying the pH.

It is used as a disinfectant for various hard surfaces, hemodialyzers, anesthesia and respiratory equipment, endoscopes, endotracheal tubes, and surgical and dental instruments.

Mechanism of action: it denatures proteins, disrupts cell wall permeability, and oxidizes sulfhydryl (-SH) and disulfide (S-S) bonds in proteins, enzymes, and other metabolites.

• Products in the Klintensiv portfolio containing peroxides include:
• Oxoklin
• Oxoklin powder
• Peroklin
• Peroklin Wipes
• Desogen aero
• Peroklin concentrated

Biguanides

Chlorhexidine has been used as an antiseptic since 1954 and is found in 3 forms: digluconate, acetate, and hydrochloride. It is a positively charged molecule that binds to negatively charged sites on the cell wall, thereby affecting cellular integrity.

It has a broad spectrum of action, without sporicidal efficacy, and with a residual effect of at least 48 hours after application to the skin. Its action is not influenced by the presence of biological fluids (e.g., blood).

It can be used for the hygienic or surgical disinfection of hands, as an antiseptic for mucous membranes and wounds (0.05%), as a disinfectant for surfaces (0.05%), and for instruments (0.1–0.5%). It is also used for the antiseptic treatment of burns and in combination with ethyl or isopropyl alcohol (0.5–1%), not being volatile like them.

Chlorhexidine 2% is recommended by the CDC (Centers for Disease Control and Prevention) as the first choice for catheter insertion site care, being highly effective in preventing local infections.

It is important to monitor for the appearance of mild allergic reactions (pruritus, edema) which can be followed by severe ones. Sometimes, allergic reactions to chlorhexidine can be severe (anaphylactic shock or cardiac arrest).

Mechanism of action: as a positively charged molecule that binds to negatively charged sites on the cell wall, it affects the cellular integrity of microbial agents.

• Products in the Klintensiv portfolio containing biguanides include:
• Klintensiv Davera Soap
• Klintensiv CHDG Soap
• Dezidiol spray
• Dezidiol Wipes
• Klintensiv Alchosafe

Conclusions

Bibliography

1. https://www.cdc.gov/infectioncontrol/guidelines/disinfection/references.html
2. https://www.aefa.es/wp-content/uploads/2014/04/Antiseptics-and-Disinfectants_Activity-action-and-resistance.pdf
3. Antiseptic Stewardship. Biocide Resistance and Clinical Implications – Günter Kampf