I'KODrC'noN ol' ANTIIUOTirS 



229 



(■ill show similar ant il)i()ti(' spectra and can, 

 I hci'cldrc, l)c ^limped l()jj;ct licr, 'Tlicy arc all 

 i)asic antibiotics, soluble in water and acli\c 

 against gram-posit i\(\ ,tirani-ne,nati\-e, and 

 acid-fast l)acteria; they are not acti\-e upon 

 \Mrusos. They show marked dilTerences, how- 

 e\"er: Streptothricin is ad \\v on a lai'.i;;c nuin- 

 Iht of fungi anil inactixe on />. <■( r( iis. Strep- 

 tomycin is active on only xciy few fungi, 

 mostly phycomycetes, and on B. cereus. Ne- 

 omycin is not active on fungi, but is active on 

 B. cercus. These three antibiotics vary in the 

 degree of their actixity on individual bac- 

 terial species and strains; they also differ 

 in their toxicity to animals. These antibiotics 

 each represent a group oi- a complex of 

 closely related chemical substances, the in- 

 di\idual components showing differences 

 in their antimicrobial activities, which are 

 largely quantitative in nature. 



The same relationships and differences are 

 found in the tetracychne group of antibiotics. 



Some antibiotics are characterized by very 



Table 62 



Comparative atitibiotic spectra uf streptomycin 



and streptothricin 



On basis of crude, ash-free drj^ material 



Organism 



B. subtilis 



B . mycoides 



B. cereus 



B. megaterium . . . 

 Staph, aureus. . . . 



Sar. lutea 



M. phlei 



M. tuberculosis . . 



Ph. pruni 



E. coli 



Serr. marcescens. 

 Aer. aerogenes. . . 



Pr. vulgaris 



Ps. fluorescens . . 

 Ps. aeruginosa . . . 

 CI. butylicum . . . . 



narrow antimicrobial spectra: \'ioinycin is 

 actixc cliicdy against .1/. sHKynidlis and cer- 

 tain other m>('ol)actei'ia. Other antibiotics 

 ha\-e wide spectra, sucii as chloi'amphenicol 

 and the tetracyclines, which are acti\'e not 

 only ui)()n gram-p()siti\'e and gram-negative 

 bacteria, but also upon ricketlsiac and the 

 lai'ger \iruses. 



The development of resistan(u> among sen- 

 sit i\-e bacteria against specific antibiotics and 

 the problems of cross-resistance among the 

 ditTerent antibiotics can also be utilized for 

 the purpose of classifying and identifying 

 antibiotics. 



Production of Antibiotics 



For the production of antibiotics, complex 

 organic media, containing j^east extract, soy- 

 bean meal, meat extract, or similar materials, 

 are usually required. Synthetic media can 

 also be used. O'Brien et al. (1952) demon- 

 strated that as good yields of streptomycin 

 can be obtained on a proper synthetic me- 

 dium as on a complex soybean meal-glucose 

 medium. Such a synthetic mediiun consists 

 of glucose, glycine, sodium acetate, magnes- 

 ium sulfate, potassium phosphate, and traces 

 of iron, zinc, copper, calcium, and manga- 

 nese. The acetate can be replaced by gluta- 

 mate or succinate. 



For maximum yields, however, specific 

 media and specific conditions must be de- 

 veloped, not only for each antibiotic, but for 

 each strain of each organism producing a 

 given antibiotic. 



Classification of Antibiotics 



Various systems have been proposed for 

 the classification of antibiotics of actinomy- 

 cetes. Kurosawa suggested the combination 

 of the ability of different organisms to utilize 

 specific carbohydrates and to form antibiot- 

 ics as a basis for the classification of actino- 

 mycetes. Six groups of actinomycetes were 

 thus recognized: 



L Those organisms that are rhamnose- and 



