ANTIMICROBIAL AND ANTITUMOR ACTIVITIES 



79 



ganisms. The tetracyclines and chloram- 

 phenicol are active against both gram-posi- 

 tive and gram-negative bacteria, including 

 the Clostridia and the brucellae. The last 

 two groups of antibiotics are also active 

 upon the rickettsiae and psittacosis-lymph- 

 ogranuloma group of intracellular parasitic 

 organisms, Init the first group is not. 



The phenomena of cross-resistance and 

 strain variation further characterize the 

 above three groups of antibiotics, as will be 

 discussed later (Chapter 10). The literature 

 on the various antibiotics is so extensive that 

 no attempt could be made to cover it in 

 even a limited way. Only a few pertinent 

 references can be presented here on the 

 antimicrobial activities of some of the anti- 

 biotics produced by actinomycetes, espe- 

 cially those that have been well recognized 

 and are of established therapeutic value. 



Finland and Haight (1953) isolated 500 

 strains of hemolytic, coagulase-positive cul- 

 tures of Staph, aureus from clinical material 

 and tested them for sensitivity to various 

 antibiotics (Table 28). They observed that 

 with an increase in the use of various anti- 

 biotics in clinical practice, there was a sig- 

 nificant increase in the proportion of bac- 

 terial strains resistant to the antibiotics, 

 notably to chlortetracycline and oxytetra- 

 cycline. Of the total strains tested, about 

 three fourths were resistant to penicillin, 

 one fourth to chlortetracycline, and one 

 third to oxy tetracycline. 



Potee et al. (1954) made a study of 119 

 strains of freshly isolated cultures of Pro- 

 teus. They comprised 86 strains of /-'/•. 

 mirahilis, 12 of Pr. vulgaris, 15 of Pr. m<>r- 

 ganii, and 6 of Pr. rettgeri. The sensitivity of 

 these strains to 10 antibiotics varied greatly, 

 depending on the species, as shown in 

 Tables 29 and 30. They were all found to 

 be invariably resistant to erythromycin, al- 

 though a few showed some sensitivity. Most 

 of the strains were resistant to streptomycin, 

 especially after the previous use of this 



Table 28 

 Distribution of 500 strains of Staph, aureus accord- 

 ing to grade of resistance to five antibiotics which 

 have been in common use (Finland and Haight, 

 1953) 



*S = sensitive; I = intermediate; R = re- 

 sistant. 



antibiotic. Many strains were relatively 

 sensitive to neomycin, which had not been 

 used previously in these particular cases. The 

 sensitivity to chloramphenicol and the tetra- 

 cyclines varied greatly among the species 

 and strains. In general, neomycin and chlor- 

 amphenicol were most active; streptomycin 

 came next; erythromycin and penicillin were 

 least active. Bacitracin and polymyxin 

 showed no activity. Almost all strains of all 

 species were inhibited by neomycin in con- 

 centrations of 25 to 100 Mg per ml. This 

 antibiotic was slightly more active in vitro 

 against most of the strains than were strep- 

 tomycin and chloramphenicol (Tables 29 and 

 30). When the above results were compared 

 to the findings obtained in 1949, no definite 

 increase in resistance of Proteus to penicillin 

 or to streptomycin was found; there was a 

 slight increase in resistance to chlorampheni- 



