Disinfection Studies the Effects of Temperature and Hydrogen Ion Concentration Upon the Viability of Bact. Coli and Bact. Typhosum in Water

Abstract

Exposure to extremes of temperature and of hydrogen ion concentration produces an accelerated death rate of bacteria. These aTe typical conditions of ordinary disinfecting procedures. Temperatures and hydrogen ion concentrations in the zones between those which are favorable and those which are distinctly lethal may be expected to produce an adaptation in the organisms or a comparatively slow death rate, knowledge of which may reveal the conduct of bacteria under moderately unfavorable conditions in nature, and add to our understanding of certain phases of disinfection. The object of this study was to investigate the effects of variations in moderate temperature and moderate hydrogen ion concentrations upon the death rate in water and dilute buffer solutions. The experimental method imposed sub-lethal conditions upon the bacteria in contradistinction to the accelerated death induced by ordinary disinfecting procedures. It has been found in unbuffered media like distilled water or tap water that the death rates vary coincidently with apparently unimportant shifts in hydrogen ion concentration. When the pH factor is controlled by means of M/500 buffers, the death rates are stabilized so that comparisons become possible. The I Published by permission of the Surgeon General. Thesis submitted in partial fulfilment of the requirements for the degree of Doctor of Philosophy at Yale University.

Rapid Destruction of Bacteria in Commonly Used Diluents and Its Elimination

“…Not all types of bacteria die rapidly when placed in water or saline. The coli-aerogenes group and the morphologically and biochemically related Salmonella and Proteus groups can survive, in undiminished numbers, for many hours and even days in water (Cohen, 1922;Osborne, 1955, 1956). But as has been indicated, many bacteria, including aerobic sporeformers, pseudomonads, and other common inhabitants of foods die very rapidly, within minutes, when suspended in water or saline.…”

A Study of the Bactericidal Action of Ultra Violet Light

“…It is typical of these reactions, such as the killing of bacteria by disinfectants (12,13,14), the limitation of the duration of life of fruit flies by untoward conditions of environment (15), or the hemolysis of erythrocytes by specific antibodies, or by ultra violet light (16) that the middle portion of the experimental curve may be reproduced mathematically by the equation that also describes the course of monomolecular chemical reactions. The formula tempts one to speculate, by analogy, on the nature of the fundamental biological reactions involved.…”

The F. D. A. Test for Antiseptic Value of Liquor Antisepticus**Scientific Section, A. Ph. A., Portland meeting, 1936.

“…Others working with Staphylococcus aureus have experienced this day-to-day variation in the same culture, and Cohen (1922) found a probable error of 2 or 3 per cent under the most ideal conditions, and as high as 10 per cent in most of his work. Smyth (1934) published the results of his 'detailed experiments on factors influencing the phenol resistance of Staphylococcus aureus, and concluded that any small deviation, such as concentration of disinfectant and of cells, the temperature a t which the disinfection test is conducted, the age of the culture and even a 1' difference in the incubator temperature, will cause variations.…”