. Les actinomycètes. Actinomycetales. 238 Les actinomycètes, Tome I. 2 4 6 8 10 unités d'GRISEIN /ml Figure 90. Effet de la concentration d'antibiotiques sur le développement de la résistance par E. coli dans l'agar : O, Gri.sein seul ; un, Grisein  + strepto- mycin 1 mg/ml ; n  + 2 Grisein la streptomycine/xg/ml. (Reprodnced de : Reynolds, D. M. et Waks- homme. S. A. J. Bacteriol. 55 : 750, 1948). Les macrolides La première de ces antibiotiques (erythromy- cin) a été isolé l)o JVIcCkiire et al. (1952) d'une culture de "S'. enjthreus. C'est un composé de base, soluble dans l'eau, l'alcool et d'autres matières organiques s()lv(La GSTI. Il

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. The actinomycetes. Actinomycetales. 238 THE ACTINOMYCETES, Vol. I. 2 4 6 8 10 UNITS OF GRISEIN /ml Figure 90. Effect of antibiotic concentration on development of resistance by E. coli in agar media: O, Gri.sein alone; A, Grisein + strepto- mycin 1 Mg/ml; n Grisein + streptomycin 2/xg/ml. (Reprodnced from: Reynolds, D. M. and Waks- man. S. A. J. Bacteriol. 55: 750, 1948). The Macrolides The first of these antibiotics (erythromy- cin) was isolated l)y JVIcCkiire et al. (1952) from a culture of »S'. enjthreus. It is a basic compound, soluble in water, alcohol, and other organic s()lv(Mits. It has significant ac- tivity against gram-positive organisms and some of the more important gram-negati'e bacteria, such as the Neisseria, Ilemophibis, and Brucella groups; it is also active upon rickettsiae, the larger viruses, and some pro- tozoa. A number of other ervthromvciu-like com- pounds ha^•e been isolated and descril)ed un- der a variety of names, such as picromycin, magnam, ycin (carbomycin), oleandomycin, methymycin, and spiromycin. Novobiocin This antibiotic is produced by S. niveus and by S. spheroides. It has been isolated simultaneously in different laboratories and described under different names (strepto- nivicin, cathomycin, cardelmycin, vulcano- mycin, etc.). It is highly active against Staph, aureus, as well as against a variety of other gram-positive and some gram-negative bac- teria, but it causes allergic dermatitis. Streptovariciii This orange-red group of antibiotics, which contains at least five closely related components, was isolated from the culture of an organism described as S. spectabilis. It is active against various gram-positive, gram- negative, and especially acid-fast bacteria. The Polyenes Most of the previously listed antibiotics are active primarily on bacteria and have only a limited activity on true fungi. There are, however, a number of antibiotics pro- duced by actinomycetes that have a highly selective activity upon fungi. As poin

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