Psychrophilic Bacteria—A Review

Publisher Summary The chapter aims to show which storage temperatures are sufficiently low to prevent growth of food-poisoning organisms, fecal indicators, and psychrophiles in frozen and chilled foods. These three groups of organisms are treated separately. Growth of the first group creates a health hazard; the presence of the second usually indicates fecal contamination; and the psychrophiles are not considered to be health hazards, but they cause deterioration and spoilage of foods even at temperatures considerably below 0°C. Of these three groups, the food-poisoning organisms and the fecal indicators are mesophiles. Many species of psychrophilic bacteria, yeasts, and molds can cause deterioration and spoilage of food a t 0°C and below. All of these are considered in determining the maximum storage temperature that will prevent microbial growth and consequent deterioration of foods. The chapter presents a compilation of available data listing the minimum temperatures at which these three classes of organism have been observed to grow. It discusses the relationship between environmental factors and minimum growth temperatures. It also considers the question of why there is, for a given organism under given conditions, a minimum temperature below which no growth is observed even after prolonged incubation. Each microorganism has a temperature minimum below which growth cannot be detected even after prolonged incubation in the presence of the nutrients that support growth at higher temperatures. Thus, the chapter considers several factors that may limit growth as the temperature is reduced.

Minimum growth temperatures for food-poisoning, fecal-indicator, and psychrophilic microorganisms.

Vitalfärbung und Vitalfluorochromierung pflanzlicher Zellen und Gewebe

The validity of the coliform test as an “index to sanitation” is open to question. The presence of E. coli in pasteurized milk can mean so many things including survival of pasteurization, growth, ...

Escherichia coli as an index to sanitation

https://lib.dr.iastate.edu/cgi/viewcontent.cgi?article=3181&context=rtd

Quality of manufacturing-grade bulk-tank milk

The Effect of Temperature on Coliform Organisms in Milk and Cream

In describing a method of testing for the return of color in decolorized fuchsin for use in Endo Medium, French states that variations in hydrogen ion concentration fail to influence the appearance of color in this medium.Duplications of this test were made using alcoholic and aqueous solutions of fuchsin and both sodium sulfite and sodium bisulfite as decolorizing agents.In the decolorized alcoholic solutions of fuchsin the color failed to reappear when formalin was added, but a small amount of a weak solution of lactic acid caused the color to return.Alcoholic solutions of fuchsin failed to decolorize in sodium bisulfite solutions until a few drops of NaOH were added. The color, then, reappeared immediately.Solutions of peptones to which fuchsin had been added were substituted for the original fuchsin solution. Alcoholic and aqueous solutions of fuchsin were added to equal amounts of a 1% peptone solution. The peptone solutions varied in their hydrogen ion concentration and the results showed that those...

A Consideration of French's Test of Basic Fuchsin for Endo's Medium

A study was made of the extrinsic bacteriostatic value of different lots of two brands of several tri-phenyl methane dyes. Staphylococcus aureus Rosenbach and Bacterium communior Holland were chosen as the test organisms. The conclusions are as follows: (1) Recent lots of the two brands of each dye possess practically the same bacteriostatic value; (2) the ethyl group in brilliant green appears to be responsible for the marked inhibition of the colon organism by this dye; (3) the bacteriostatic action of a dye is influenced by the H-ion concentration and constituents of the medium and by the amount of the inoculum; (4) the therapeutic value of a dye cannot be judged by tests in vitro.

The Titration of Dyes for their Bacteriostatic Action

Bacteriologists have long recognized the need for a reliable test to detect the presence of colon organisms and to differentiate between the various species of that group. In 1904 Endo published a test which has been recognized ever since as a valuable and a desirable one. It has been widely used, especially in this country, for studying members of the colon group of bacteria. This medium contains an indicator in the fonn of decolorized basic fuchsin. When Bact. coli is grown on Endo agar it brings about a reaction which leads to a restoration of the color of the ftichsin in the colony while other bacteria have no such effect on decolorized fuchsin. This is an excellent and efficient method for detecting Bact. coli in contaminated materials, but it has certain disadvantages which have not, as yet, been entirely overcome. The method for making this medium is described by Endo as follows:

Color diffusion in endo agar.

The writer has made an investigation of various samples of basic fuchsin for use in the Endo medium for differentiating the bacteria of the colon-typhoid group. Various different concentrations of the fuchsin samples have been used in making the media. The conclusions are as follows:American made fuchsins differ markedly in their alcohol solubility properties. They contain materials which are very readily soluble in 95% alcohol, but which are precipitated by sodium sulphite.This precipitation may be prevented by increasing the dilution of the fuchsin in alcohol.In order to secure more dependable results in the use of decolorized basic fuchsin as an indicator in Endo Agar, it is advisable to test the fuchsin in different dilutions in alcohol in order to secure a completely decolorized solution. It is also advisable to carefully test those fuchsins which decolorize only in high dilutions with a known organism in Endo agar before relying on it as a satisfactory indicator for the presence of sewage organisms.

Elizabeth F. Genung

Papers

The Effect of Temperature on Coliform Organisms in Milk and Cream

A Consideration of French's Test of Basic Fuchsin for Endo's Medium

The Titration of Dyes for their Bacteriostatic Action

Color diffusion in endo agar.

Basic Fuchsin as an Indicator in Endo's Medium