MICROBES man's MIGHTY MIDGETS 47 



broad-spectrum drugs has been their capacity to remove effectively the bac- 

 terial flora from the intestinal tracts of patients undergoing treatment. In 

 consequence, the yeasts, species of Candida, which are generally present in 

 small numbers, may flourish in the absence of competing microorganisms, thus 

 giving rise to a secondary disease, monilasis, of serious proportion. Nystatin 

 offers promise in the alleviation of this condition and in other disease proc- 

 esses caused by pathogenic fungi. 



In addition to penicillin and the actinomycetous antibiotics, there are a 

 few drugs of this class produced by bacteria. None of these have wide appli- 

 cations, and they are not manufactured on a large scale, but they possess 

 invaluable therapeutic properties. The oldest of these, tyrothrycin, pro- 

 duced by Bacillus brevis and discovered by DuBos, is widely used in the 

 preparation of medicated bandages and in troches and sprays for respiratory 

 infections. The second, bacitracin, produced by B. lichenijormis, is also used 

 in medicinals for topical application and is commonly employed as a pre- 

 operative drug. It is an effective medicant in amebiasis. The third, poly- 

 myxin, produced by B. polymyxa, is especially useful in combating infec- 

 tions of the blue-pus type caused by Pseudomonas aeruginosus. Like neo- 

 mycin, it is often used in combination with other antibiotics. The total sales 

 of any one of these minor antibiotics is not great, but in the aggregate, to- 

 gether with three or four others unmentioned here, they amounted to ap- 

 proximately $20 million in 1955. 



Following the discovery that vitamin Bj:- stimulated the growth of chickens 

 and other meat animals, it was found that minute amounts of aureomycin, 

 and subsequently penicillin and other antibiotics, would produce a marked 

 growth stimulation in chickens, turkeys, pigs, and many other animals. The 

 net result of this has been to provide an additional market for antibiotics 

 which, on a weight basis, approaches for some of these the quantities used as 

 drugs. Whereas all the antibiotics exhibit this property in some measure, 

 those which have proved most useful as feed supplements are penicillin, 

 aureomycin, and bacitracin. It is not necessary that the antibiotics be highly 

 purified for use as feed supplements, although this is commonly done to 

 enhance product stability and to obviate the necessity of dual manufactur- 

 ing processes. For the year 1954 the value of antibiotics used for feed sup- 

 plementation alone exceeded $25 million. 



Two additional uses for antibiotics of enlarging proportions are their 

 application in the control of certain plant diseases and for extending the 

 marketable life of meats and other perishable foods. Of the antibiotics used 

 against plant diseases at the present time, streptomycin leads the field by a 

 wide margin, whereas aureomycin is the principal antibiotic currently em- 

 ployed for food preservation. This latter iypt of application includes the 

 storage of fish in ice containing low concentrations of the antibiotic, and also 

 a recently approved process whereby eviscerated poultry is dipped in a bath 



