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

Ortho-phthalaldehyde (OPA) was tested against a range of organisms includin g glutaraldehyde-1 resistant mycobacteria, Bacillus subtilis spores and coa t-defective spores. Glutaraldehyde (GTA) and peracetic acid (PAA) were test ed for comparative purposes. Both suspension and carrier tests were perform ed using a range of concentrations and exposure times. All three biocides w ere very effective (greater than or equal to 5 log reduction) against Esche richia coli, Staphylococcus aureus and Pseudomonas aeruginosa in suspension tests. OPA and GTA (PAA was not tested) were also very effective against S taph. aureus and Ps. aeruginosa in carrier tests. OPA showed good activity against the mycobacteria tested including the two GTA-resistant strains, bu t 0.5% w/v OPA was found not to be sporicidal. However, limited activity wa s found with higher concentrations and pH values. Coat-defective spores wer e more susceptible to OPA, suggesting that the coat may be responsible for this resistance. The findings of this study suggest that OPA is effective a gainst GTA-resistant mycobacteria and that it is a viable alternative to GT A for high level disinfection.