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A SURFACE FILM METHOD OF EVALUATING QUATERNARY AMMONIUM COMPOUNDS
Author(s) -
WHITT EUNICE W.
Publication year - 1958
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.1365-2672.1958.tb00143.x
Subject(s) - agar , ammonium , strips , nutrient agar , suspension (topology) , chemistry , metal , chromatography , agar plate , materials science , bacteria , biology , metallurgy , composite material , organic chemistry , genetics , mathematics , homotopy , pure mathematics
SUMMARY: A suspension of bacteria was evenly spread on descaled stainless steel strips and air dried. The strips were put into the QAC solution and after the required period the bactericidal action was stopped by adding a neutralizing agent. The strips were covered with nutrient agar and incubated at 37° for 24 hr to enable the surviving organisms to grow into colonies. On removing the thin layers of agar from the strips the colonies were left adhering to the metal. They were stained with carbol fuchsin and counted using a dissecting microscope. Using the recommended strength of a QAC‐detergent solution (200 p/m QAC) and an exposure time of 2 min a mortality of at least 99·58% was obtained. The temperature of treatment had little effect on this, though in experiments with added organic matter or lower concentrations of QAC the temperature was important.