title: Synergistic sporicidal effect of ethanol on a combination of orthophthalaldehyde and didecyldimethylammonium chloride.
abstract: The objective of this study was to evaluate the potential synergistic effect of ethanol on a combination of orthophthalaldehyde (OPA) and didecyldimethylammonium chloride (DDAC) against the spores of Bacillus subtilis var. Niger. The quantitative carrier test for sporicidal testing of high-level disinfectants according to the guideline of China (Technical Standard for Disinfection 2002) was used as method. Considerable synergistic effect was observed after a 30-min treatment at 20°C. There was an augment in mean log reduction as the concentration of DDAC was increased ranging from 0·2 to 3 g l(-1) in combination with 6 g l(-1) OPA. Ten and 20% ethanol in combination with 6 g l(-1) OPA and 2 g l(-1) DDAC caused more than a 3-log reduction while either 6 g l(-1) OPA, 2 g l(-1) DDAC and 20% ethanol alone or a combination of two of the three agents produced less than a 1-log reduction. Further, 40-min exposure time of combination of OPA, DDAC and 20% ethanol led to greater than a 5-log reduction in spores, and no spore growth was observed following 60- and 90-min exposures.
  
  
  CONCLUSIONS
  Orthophthalaldehyde (OPA) is very effective at concentrations far lower than its recommended in-use concentration of 0·5% (w/v) and is equally effective against both the gram-negative and gram-positive bacteria. However, it shows lower activity against spores. The synergistic sporicidal effect exhibited by ethanol on a combination of OPA and DDAC can be considered to enhance sporicidal activity for using in situations of sterilization, to reduce in-use concentration of OPA used alone, which may minimize its side effect. OPA may be a more satisfactory and the first-choice agent to replace glutaraldehyde (GTA) as a high-level disinfectant for medical devices.
authors.affiliation: Evaluation and Research Center for Disinfection, Institute of Disease Control and Prevention, Academy of Military Medical Sciences, Beijing, China.
authors.forename: G
authors.initials: G
authors.lastname: Yuan
authors.forename: Q
authors.initials: Q
authors.lastname: Wei
authors.forename: J
authors.initials: J
authors.lastname: Tie
authors.forename: C
authors.initials: C
authors.lastname: Wang
authors.forename: L
authors.initials: L
authors.lastname: Rao
authors.forename: W
authors.initials: W
authors.lastname: Zhang
mesh_terms: D001412:Bacillus subtilis / Q000187:drug effects* / Q000502:physiology; D004202:Disinfectants / Q000494:pharmacology*; D004203:Disinfection; D004357:Drug Synergism; D000431:Ethanol / Q000494:pharmacology*; D008826:Microbial Sensitivity Tests; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology*; D013171:Spores, Bacterial / Q000187:drug effects; D009764:o-Phthalaldehyde / Q000494:pharmacology*
chemical_list: D004202:Disinfectants; D000644:Quaternary Ammonium Compounds; D000431:Ethanol; D009764:o-Phthalaldehyde; C027118:didecyldimethylammonium
keywords: high-level disinfectant; orthophthalaldehyde; sporicidal activity; synergistic effect