Natural and Acquired Resistance of Escherichia coli to Neomycin

Abstract

-The extent of the corona of stars that surrounds the galactic system has been examined on the basis of current studies of galaxies and variable stars in the anticenter region of the Milky Way. The vari-ables of the cepheid family found in galactic latitudes of less than ten degrees can rarely be used to measure the extent of the Milky Way because the interstellar absorption is heavy; but on the borders of the Milky Way, where the galaxy counts indicate the degree of transparency, a considerable number of cluster type variables have shown that the coronal population extends to anticenter distances equal to the distance separating us from the center of the Milky Way. The distances from the center of the galaxy to a fourth of these outlying variable stars exceed fifteen kiloparsecs; similar distances were found previously for a few variables in the galactic polar caps. The greatest distance exceeds twenty kiloparsecs. The computed distances above and below the galactic plane (z in table 1) show that few if any of these cluster variables are members of the galactic discoid. 1 His mean value of s is 9.0 4± 0.6 kpc. 2 These PROCEEDINGS, 25, 423-428 (1939); Harvard Reprint 173. Introductory.-The problem of development of resistance of bacteria and other organisms to the action of bacteriostatic and bactericidal agents in general and to chemotherapeutic substances in particular has become in-creasingly serious with the extensive use of antibiotics in the treatment of infectious diseases of men and animals. Different compounds exhibit marked differences in the nature and speed of development of resistance, thus pointing to differences in their mode of action upon bacteria and other microorganisms. Some antibiotics, like streptomycin and more especially grisein, favor rapid development of resistance among sensitive organisms. Others, like penicillin, favor development of resistance among various bac-teria only upon continued use. Moreover, penicillin leads to the develop-ment of resistance only among certain bacteria and not at all or to a lesser degree among other organisms; the rate with which such resistance de-velops and the degree of resistance attained are not so great as for strep-tomycin. Aureomycin and terramycin do not allow the rapid develop-843