The Estimation of Bactericidal Activity from Extinction Time Data

Abstract

Summary A new method for the determination of extinction time data is described. The method has been employed for the disinfection of Bact. coli by aqueous solutions of phenol over a range of concentrations and death times ranging from 2 to over 100 minutes. The use of extensive replication, short sampling intervals, and constant sample volumes withdrawn immediately after inoculation of the bactericide are among the chief features of the technique. Estimates of the mean extinction time obtained from the data are of reproducibility within limits sufficiently close to invalidate other extinction time methods, and are of comparable value with those obtained by the use of any other techniques. 5 The method has been satisfactorily applied to systems containing water-insoluble phenols solubilised in solutions of soaps (Berry and Bean9) where clumping of the test organisms might completely invalidate other methods of estimation of bactericidal activity.