The Effect of Concentration of Dyes on Differentiation of Enteric Bacteria on Eosin-Methylene-Blue Agar

Abstract

Holt-Harris and Teague introduced eosin-methylene-blue as an indicator for differentiation of the colon from the typhoid-dysentery group of bacteria in 1916. Their medium consisted of 1 per cent Witte's peptone, 0.5 per cent beef-extract (Liebig's), sodium chloride, sucrose and lactose, solidified with 1 per cent agar. The reaction was adjusted to + 0.8 per cent normal acid. The medium was cleared with egg whites, filtered, and sterilized in the Arnold for 30 minutes at 100°C. on three successive days. They recommended, as an indipator, 2 ml. of a 2 per cent yellowish eosin and 2 ml. of a 0.5 per cent methylene blue per 100 ml. of the medium. The medium was very satisfactory for its purpose, but the details of preparation made it rather cumbersome and the necessitated change of peptones after the war, coupled with resultant differences in reaction of the medium adjusted on a total acidity scale, tended towards variable results in the hands of different investigators.Levine, in 1918, suggested a simplified medium in which Difco peptone was employed as a base, di-potassium phosphate (0.2 per cent) was utilized as a buffer, to automatically adjust the reaction of the medium to a desired point, and sterilization at 15 pounds for 15 minutes in the autoclave was substituted for the more cumbersome Arnold intermittent sterilizing process. To this basal medium was added 5 ml. of a 20 per cent sterile lactose solution, 2 ml. of 2 per cent yellowish eosin, and 2 ml. of a a per cent methylene blue per 100 ml. of melted basal medium. This medium was designed primarily for the purpose of differ-* If desired, all constituents may be added prior to sterilization.

An Evaluation of Factors Affecting the Survival of Escherichia coli in Sea Water1

“…agar (Levine, 1943) and Tergitol 7 agar (Chapman' 1947) favor growth of E. coli and facilitate its identification. The development of E. coli on selective as well as on nonselective agar media was examined.…”

“…Various selective media for the isolation and enumeration of coliform bacteria are available commercially. , La Lima, Honduras, C. A.agar (Levine, 1943) and Tergitol 7 agar (Chapman' 1947) favor growth of E. coli and facilitate its identification. The development of E. coli on selective as well as on nonselective agar media was examined.…”

A culture medium for screening 16S rRNA methylase-producing pan-aminoglycoside resistant Gram-negative bacteria

“…Based on our experience of development of several screening media, the optimal screening medium retained was based on the Eosine-Methylene-Blue (EMB) medium (product no. 70186; EMB Fluka, Saint-Louis, MO) that is selective for Gram negatives (Levine, 1943). This medium may also contribute to species identification by differentiating lactose fermenters (black colonies) from most of the nonfermenters (colorless or light lavender).…”

Genetic and Biophysical Study of R Plasmids Conferring Sulfonamide Resistance in Shigella Strains Isolated in 1952 and 1956

“…Luria broth supplemented with 2.5 x 10-3 M CaCl2, termed Z broth, was used for experiments with phage Plkc. Eosin methylene blue medium was prepared as described by Levine (29), except that lactose was omitted and 0.1% (wt/vol) glucose was added.…”