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Neutralization efficacy of Dey‐Engley medium in testing of contact lens disinfecting solutions
Author(s) -
Sutton S. V. W.,
Wrzosek T.,
Proud D. W.
Publication year - 1991
Publication title -
journal of applied bacteriology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.889
H-Index - 156
eISSN - 1365-2672
pISSN - 0021-8847
DOI - 10.1111/j.1365-2672.1991.tb02948.x
Subject(s) - benzalkonium chloride , contact lens , thimerosal , disinfectant , chemistry , cetrimide , chromatography , chlorhexidine , microbiology and biotechnology , medicine , biology , dentistry , organic chemistry , dermatology , ophthalmology
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 TM (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.