These authors suggest simplification of the technic by reducing the lactose content by addition of gentian violet, also Pasteurization in place of autoclaving. The announced value of gentian violet for preliminary enrichment of colon cultures is sustained, with cleaner plates and readier identification of colonies. Gentian violet has also advantages in ensuring keeping qualities in the broth.THE lactose broth prescribed by the acidity was produced was not reached committee of the American Public even after prolonged a u t o c 1 a v i n g. Health Association (1917) contains Chamot and Sherwood2 advocated the 0.3%b beef extract, 0.5%o peptone, and use of media of special composition, 1%o lactose. It is adjusted to neutral omitting the usual addition of beef exreaction with phenolphthalein and steri-tract and increasing the percentage of lized in the autoclav at 15 pounds for 15 peptone. It was their conclusion that minutes. "Any type of fermentation beef extract stimulated growth of Bact.tube may be used provided it holds at communis, but not in proportion to the least four times as much medium as the trouble and labor involved. Salter3amount of water to be tested." (The showed that Bact. communis in peptone later directions of the committee (1920), water (without sugars) reached the issued since the completion of the work maximum rate of growth more quickly herein described, reduce the amount of in concentrated peptone water; a 2%o lactose to 0.5%o.) peptone solution appeared to be superiorThe modifications suggested in this to broth with 0.3%o beef extract and paper are: elimination of beef extract, 0.5%o peptone. Bronfenbrenner and reduction of the per cent of lactose, Schlesinger4 concluded that in lactose sterilization without autoclaving, and re-broth the amount of gas produced induction of the volume of broth used in creased directly with the concentration fermentation tests on 10 cc. portions of of buffer. water tested. Concerning lactose Theobald Smith3Beef extract *occasions certain diffi-stated that a concentration of 1%o gluculties in the preparation of neutral cose or lactose would be a decided detribroth. It undergoes progressive hydrol-ment to Bact. coli and soon lead to its ysis with successive heatings. Anthony destruction. He advocated addition of a and Eckrothl found that beef extract minimum essential concentration of adjusted to neutrality and thereafter sugar (glucose) of 0.1% to bouillon. subjected to sterilization in the autoclav Berman and Rettger3 found that Bact. was slightly hydrolyzed; with meat in-coli failed to attack peptone appreciably fusions the point at which no further in the presence of utilizable sugars, and 203 l
Attempts to bring cultures isolated from routine water samples in the laboratory of the Illinois State Water Survey within the tentative classification of the committee of the American Public Health Association (1917) reveal certain inadequacies of the scheme, some of which have been previously noted in the literature without emphasis. ANOMALOUS METHYL RED-VOGES-PROSKAUER REACTIONS Correlation of the methyl red reaction with the Voges-Proskauer reaction has been adjudged almost complete for low ratio organisms; but for high ratio types, a very considerable number of exceptions have been noted. Berrier, McCrady and Lafreniere (1916), applying these tests to 450 organisms isolated from feces, city sewage and grains, found the Voges-Proskauer and methyl red tests to agree completely with the generally accepted standard tests for Bact. coli organismns when applied to 197 strains from human feces, except in one instance. Applied to grain and sewage cultures tfe correlation was found in 80 per cent of the cases. Levine (1916) cites a small group of organisms isolated from soil, resembling Bact. aerogenes with respect to gas formation from various carbohydrates, etc., which did not give the Voges-Proskauer reaction and were neutral to methyl red after three days' incubation at body temperature. Some did not give the Voges-Proskauer reaction and were not alkaline to methyl red until the fifth or seventh day of incubation. These resemble closely a form described by MacConkey, who records the Voges-Proskauer reaction as positive or negative.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.