Effects of penicillin, streptomycin, and tetracycline on N. gonorrhoeae isolated in 1944 and in 1957.

N. gonorrhoeae is a species which was originally highly sensitive to penicillin (Cohn and Seijo, 1944; Frisch, 1944; Carpenter, Bahn, Ackerman, and Stokinger, 1945; Lankford, 1945; Meads, Ory, Wilcox, and Finland, 1945; Romansky, 1946; Kenedy and Alfoldy, 1947; Romansky and Robin, 1947; Hughes and Carpenter, 1948; Hawks and Greey, 1948; Cohn, Grunstein, Goldberg, and Crane, 1949; Mills, 1949; Storck, Rinderknecht, and Fries, 1949; Zierz and Eckert, 1949); however, by serial subcultivation on media containing increasing concentrations of penicillin (Bahn, Ackerman, and Carpenter, 1945; Carpenter and others, 1945; Miller and Bohnhoff, 1945; Mills, 1949), the sensitivity can be reduced. In accordance with earlier findings with many other micro-organisms, it is rather difficult to increase the in vitro resistance to penicillin compared with, for example, streptomycin (Miller and Bohnhoff, 1945, 1946). When the present investigations were started, only a few reports indicated the in vivo and in vitro existence of strains with a decreased sensitivity to penicillin (Franks, 1946; Duemling and Horton 1947). It was generally agreed, however, that very resistant strains did not occur (Dowling, 1954; Gartmann and Knapp, 1954; Marcuse and Hussels, 1954; Mark, 1954; Fischer, 1955; Del Love and Finland, 1955; Finland, 1955, 1958; Lodin, 1956a,b; World Health Organization, 1957a,b; Marchionini and Rockl, 1957). Some authors had reported a change in the distribution of the in vitro concentrations necessary for inhibition or killing of N. gonorrhoeae (Gocke, Wilcox, and Finland, 1950; Schreus and Schummer,