ANTIBIOTIC GROUPS 169 



previous two groups by their antibiotic spectra and by the use of resistant 

 bacterial strains. 



6. The viomycin group. These are basic polypeptides, which contain 

 guanidine or creatinine or both, and are active against the acid-fast bacteria. 



7. The tetracycline-chloramphenicol group. Members of this group are 

 active against gram-positive and gram-negative bacteria, rickettsiae, and 

 larger viruses but not against fungi and smaller viruses. They are relatively 

 nontoxic and can be readily absorbed from the digestive system. They are 

 neutral or amphoteric, soluble in organic substances and to a more limited 

 extent in water. 



8. The erythromycin-carbomycin group. These are active largely against 

 gram-positive bacteria, rickettsiae, and larger viruses, to only a limited 

 extent against gram-negative bacteria and mycobacteria, and not against 

 fungi and smaller viruses. They are basic compounds of limited toxicity. 



9. The antifungal group active also upon bacteria and actinomycetes. 

 They are pigmented and nonpigmented, soluble in organic solvents and to 

 only a limited extent in water. 



10. The antifungal group active only against fungi and not against bac- 

 teria and actinomycetes. Some of these substances are active primarily 

 against yeasts and yeast-like fungi, whereas others are also active against 

 filamentous fungi. They are soluble primarily in organic solvents; some are 

 also soluble in water. 



11. The anti-protozoan group. These substances are active selectively 

 against various protozoa, such as spirochetes, trichomonads, trypanosomes, 

 and amoebae. Some are also active against certain bacteria, notably cocci 

 and other gram-positive bacteria, or against yeasts. They are acidic or 

 basic compounds, varying in solubility and toxicity. 



12. The antiviral group. These substances are active against viruses and 

 phages and not against bacteria or fungi. They appear to be highly selective 

 in their action. Little is known concerning their nature, mode of action, 

 and utilization. 



These 12 groups comprise most of the known antibiotics of actinomycetes. 

 There is no doubt that with the increase of our knowledge, the isolation of 

 more substances, the chemical purification of many of those known at 

 present, and with greater therapeutic applications, new groups will be 

 added and those listed here considerably modified. 



These groups are believed to offer a working basis for identification of old 

 and new compounds. The first eight groups are active primarily against 

 bacteria and actinomycetes, but not at all or to only a limited extent (as 

 in the case of the streptothricin group) against fungi. The ninth and tenth 



