Neutralization efficacy of Dey‐Engley medium in testing of contact lens disinfecting solutions

Abstract

A quantitative assay for the demonstration of neutralizer efficacy was developed to monitor contact lens disinfecting solutions. Adequate neutralization of disinfecting agents is essential to the accurate determination of disinfecting activity with time. This method employed the recovery of small numbers of micro-organisms from neutralizing medium containing a disinfectant. A statistical estimation of significance between treatments demonstrated that Dey-Engley medium (DE; Difco) was generally effective when tested as an agar growth medium with several bacterial test organisms. DE medium from another vendor was less effective, underscoring the need for laboratory quality control and monitoring. DE agar (Difco) adequately neutralized all solutions tested at a 1:20 dilution. The solutions included those containing Dymed (polyaminopropyl biguanide, 0.00005%), chlorhexidine (0.005%), Polyquad (0.001%), chlorhexidine (0.005%) and thimerosal (BP, 0.001%), thimerosal (BP, 0.002%) and Tris(2-hydroxyethyl) tallow ammonium chloride (0.013%), and a solution preserved with 115 ppm benzalkonium chloride (BAK). A modification of this medium was developed which retained virtually all of the neutralizing efficacy for the solutions tested while allowing the use of automated testing procedures.

Comparative lethality kinetic curves and predictive models of F‐value for Listeria monocytogenes using different sanitizers

“…Some works in the literature reports a nonlinear death rate for different microorganisms exposed to different disinfectants (Campbell and Dimmick 1966;Turners 1983;Sutton et al 1991), corroborating the results obtained in the present work.…”

Miraflow, Soft Contact Lens Cleaner

“…The residual active ingredients of MPSs, that is, polyhexamethylene biguanide (PHMB), in the samples were neutralized by adding an equal volume of Dey-Engley neutralizing broth (Sigma, St Louis, MO). 6,15,25,26 The neutralized sample was serially diluted and cultured in PYG, and the number of surviving organisms was determined as described. The decrease in the number of organisms in each test solution was determined by subtraction from the number of cysts before inoculation.…”

The Use of Preservatives in Cosmetic Products and Their Efficiency Testing

“…Bazı antimikrobiyal maddelere karşı kullanılan nötralize edici ajanlar (16) . (8,33) . Bazı antimikrobiyal maddelere karşı kullanılan nötralize edici ajanlar Tablo 2'de gösterilmiştir (16) .…”