Standardization of the Methylene Blue Reduction Test by the Use of Methylene Blue Thiocyanate.
SINCE the first use of methylene blue reduction as an indicator of bacteriological quality in milk, fluid milk supplies on this continent have undergone notable improvement. Moreover, during this period it has been shown that the inaccuracies in the test increase with increasing reduction times.6' 8, 9 An effort to minimize these inaccuracies is, therefore, worth while. Because of the extensive use of this test in milk control activities, it becomes necessary to duplicate frequently the standard tablets of methylene blue certified by the Commission on Standardization of Biological Stains and recognized by the American Public Health Association in Standard Methods of Milk Analysis.' This duplication involves not only the creation of standards but also the purification or, at least, the determination of purity of the dye. Clark, Cohen, and Gibbs 2 review the difficulty, if not the impossibility, either of purification or of determination of purity of methylene blue chloride, the methylene blue salt used in these tablets.
Potentiometric Studies with Resazurin and Methylene Blue in Milk
Summary Resazurin reduces to the pink stage in approximately three-fourths of the time required for methylene blue to decolorize. Potentiometric studies indicate that this shortening of reduction time is mainly attributable to the change in shape of the time-potential curve when resazurin is present. Hourly inversion of tubes during incubation generally shortens the reduction time of good milks considerably. The incorporation of oxygen by this practice has little or no effect upon the time-potential curve during the early stages, and only transient effect later.
Le vert janus en face du bleu de méthylène dans l'essai à la réductase selon Barthel
-[6a] Cf. Marshall's « Microbiology» (London, 1919), p. 417. [7] Z. f. Immunitatsforsch. ù. -exp. Therap., 29, 343-8 (1920). [8] SPERJ-,ICH. Gentr. Bakt. Parasitenle. II, 34, 405-30 (1912) . . [9] Jour. l\licrobiol. Petrograd, 3, 77-8, 273-90 (1916): [10] HOL~I and SHERMAN. J. Bact., 7, 465-70, 583-8 (1922) ; Proc. Soc. Exp. Bio!. and Med., 21, .311 _(1924). . [Il] Abs. Bact., 3, 5, (1919). [12] JYIichigan A gr. Stat. Rept. (1915), p. 209. [12~] CLAYTON. Margarine (London, 1920, p. 127. FISCHER et GRUENERT. Zeits. Nahr. Genussm., 22, 553 (1911). [13] StorrsAgric. Exp.Stat. Bull. 79 (1914), 387-94. [14] BOKORNY. Gentr. Bakt. Parasitenk, II abt., 35, 118·97. PETERSEN. Arch. Hyg. 37, 171 (1900). [15] J. Dairy Sci., i, 114-26 (1917). [16] Gentr. Bakt., II Abt., 22, 32 (1909). [17] U. S. Bur. Anim. Incl. Bull, 84 (1906), p. 17. [18] The Butter Industry, p. 340. [19] Oentr. Bakt. II Abt., 22, 22 32 (1909). [20] MaHLER, WASHBURN et ROGERS. U. S. Dept, Agric., Bur. Anim. Ind., Annual Rept. (1909), pp. 179-85. HEWLETT. Manual of Bacteriology (London, 1921) pp. 409 et 749. [21] U. S. Dept. Agric., Bur. Anim. Ind., Circ. 153 p. 38. [22] The Butter Industry, p. 343. [23] Science, 42, 319(1915). [23a] Mykologie der Milch, (1911), p. 210. [24] The Butter Industry, p. 334. [25] J. Dairy Sci., 3, 77-106(1920). [26] The Butter Industry, p. 519. [27] J. Dairy Sci., 3, 103 (1920). [28] Trams. Farad. Soc., 16, Appendix 22-6 (1921).