Specificity of the neutralizers as the cause of errors in evaluating disinfectant efficacy: an assessment of triclosan

Abstract

Significance and Impact of the Study: The choice of an adequate neutralizing agent is essential for obtaining precise results in the evaluation of disinfectants using the dilution-neutralization method. In this study, we show that the neutralization of triclosan and some of its commercial solutions is not a simple task, requiring complex neutralizers. Moreover, the action of the neutralizer is shown to depend on the micro-organism tested. Specificity in view of the disinfectant and the micro-organism calls for performing the neutralizing assay in each particular case of application of the dilution-neutralization method. We also demonstrate that some of the neutralizers described for triclosan in previous studies are not sufficiently effective. AbstractOne of the most commonly used methods for assessing disinfectants in vitro is the dilution-neutralization test. Although it is known that using an effective neutralizer is essential for obtaining reliable results, in the case of disinfectants like triclosan, whose neutralization is more complicated, an adequate neutralizer is not always used. Here, we compare the efficacy of different neutralizers described previously, and others that have been modified, against several antiseptic formulations of triclosan. The strains of reference used were Pseudomonas aeruginosa, Enterococcus faecium, Staphylococcus aureus and Escherichia coli. The solutions of antiseptic were triclosan 2% aqueous solution, and three alcoholic solutions containing 2, 0Á068 and 0Á5% triclosan, respectively. In the dilution-neutralization test, six neutralizers with different degrees of complexity were assayed. Our results show that the antiseptic solutions studied are effective against the strains of reference, with the exception of triclosan 2% aqueous solution against Ps. aeruginosa. Most neutralizers proved ineffective, depending on the antiseptic solution and the bacterial species, particularly in the case of Staph. aureus. These findings confirm a need to test every neutralizer specifically for each disinfectant, at the maximum concentration used, and for every specific bacterial strain.

Phenotypic Resistance to Disinfectants and Antibiotics in Methicillin‐Resistant Staphylococcus aureus Strains Isolated from Pigs

“…In this method, the phase of neutralization is crucial for detaining the antiseptic action. The use of an adequate neutralizer is therefore essential, and it has been demonstrated that the neutralizer should always be tested, as there exists specificity with regard to the antiseptic and bacterial strain (Espigares et al., ; Fernández‐Crehuet et al., ). Other authors have carried out studies indicating the need to use specific neutralizers.…”

“…The disinfectants and antiseptics studied were as follows (at recommended concentration): glutaraldehyde, 20 mg/mL (2%); peracetic acid, 16.2 mg/mL (1.62%); chlorhexidine, 5 mg/mL (0.5%); benzalkonium chloride, 2.5 mg/mL (0.25%); povidone iodine, 25 mg/mL (2.5%); and silver nitrate, 100 mg/mL (10%). All the assays were carried out according to the norm UNE‐EN 1040:2006, as described previously (Espigares et al., ; Fernández‐Crehuet et al., ) adapting the volumes for use in a microtitre plate with 96 wells. All tests were carried out in triplicate, starting with homogeneous suspensions of 1–3 × 10 8 cfu/mL.…”

Efficacy of copper and silver as residual disinfectants in drinking water

“…[38] This validation test is necessary to perform to ensure that the neutralizing broth completely inhibits the action of the antimicrobials so that the duration of the time exposures are accurate. [39][40] Assay for Surviving Bacteria Bacterial samples were serially diluted in 0.01 M phosphate buffer and the surviving bacteria were enumerated in duplicate using the spread plate method on the following agar media: E. coli,…”

Antimicrobial Properties of a Biocide Based on Quaternary Ammonium Compounds plus Polyhexamethylene Guanidine and Possible Methods for Its Deactivation

“…One of the most efficient and profitable means of the inactivation biocidal compounds is the use of agents that neutralize their activity [23,24]. It was pro-posed in a number of patents to use for this purpose a deactivation solution containing Tween-80, saponin, histidine, and cysteine at concentrations of 5-50% (vol) [25,26].…”