Ortho-phthalaldehyde: a possible alternative to glutaraldehyde for high level disinfection

Area of Science:

• Microbiology
• Infectious Diseases
• Disinfection and Sterilization

Background:

• High-level disinfection is crucial for preventing healthcare-associated infections.
• Glutaraldehyde (GTA) resistance in mycobacteria presents a significant challenge.
• Ortho-phthalaldehyde (OPA) is an alternative disinfectant with a different chemical mechanism.

Purpose of the Study:

• To evaluate the efficacy of ortho-phthalaldehyde (OPA) against a range of microorganisms, including glutaraldehyde-resistant mycobacteria.
• To compare OPA's performance with glutaraldehyde (GTA) and peracetic acid (PAA).
• To assess OPA's activity against bacterial spores, including coat-defective strains.

Main Methods:

• Suspension and carrier tests were conducted using various concentrations and exposure times.
• Organisms tested included Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa, glutaraldehyde-resistant mycobacteria, and Bacillus subtilis spores.
• Comparative analysis with glutaraldehyde (GTA) and peracetic acid (PAA) was performed.

Main Results:

• OPA, GTA, and PAA demonstrated high efficacy (> or = 5 log reduction) against E. coli, S. aureus, and P. aeruginosa in suspension tests.
• OPA and GTA showed excellent activity against S. aureus and P. aeruginosa in carrier tests.
• OPA exhibited significant activity against GTA-resistant mycobacteria, but 0.5% OPA was not sporicidal; higher concentrations and pH showed limited sporicidal activity.
• Coat-defective spores were more susceptible to OPA, indicating the spore coat may confer resistance.

Conclusions:

• Ortho-phthalaldehyde (OPA) is effective against glutaraldehyde-resistant mycobacteria.
• OPA is a potential alternative to glutaraldehyde for high-level disinfection.
• Further research is needed to optimize OPA's sporicidal activity and understand resistance mechanisms.