UTILIZATION OF ANTIBIOTICS 



117 



forms are produced with difficulty, and even 

 more rarely in clinical use. 



Group 2 includes organisms that often 

 respond only slowly to therapy with anti- 

 biotics. In some cases, such as pulmonary 

 tuberculosis or staphylococcal osteomyelitis, 

 patients may impro\^e and yet retain the 

 organisms and infection for years, never 

 becoming entirely well. Resistant forms are 

 also often encountered. 



Group 3 includes organisms causing bru- 

 cellosis, t^^phoid, and some rickettsial in- 

 fections. The organism isolated during re- 

 currence remains sensitive to the antibiotic 

 originally used, and the infection will re- 

 spond to another course of therapy. 



Antibiotic resistance is particularly serious 

 in the case of staphylococci, tubercle bacilli, 

 and certain gram-negati\'e forms, such as 

 Proteus, Psoidomonas, and the coliform 

 organisms. Staph^dococcal infections due to 

 resistant strains are said to constitute the 

 most serious clinical prol)lem of antil)iotic 

 resistance. The solution of the problem of the 

 emergence of antibiotic-resistant staphylo- 

 cocci has received much attention (Dunlop, 

 1960). Combination therapy with two anti- 

 biotics has been recommended, provided the 

 organism is sensitive to each antibiotic 

 alone. Unfortunately, there is no evidence 

 that the incidence of resistant strains 

 is always reduced by combined therapy. 

 Lepper et al. (1956) used novobiocin plus 

 spiramycin in a routine manner for 6 

 months. A gradual increase in the incidence 

 of staphylococcus resistance to each anti- 

 biotic occurred despite this combination 

 therapy (see also Kass, 1955, and Velu, 

 1958). The preventive use of antibiotics must 

 also be mentioned (By waters, 1960; Taylor, 

 1960). 



Animal Diseases 



On a par with the revolution that took 

 place in the treatment of infectious diseases 

 in man as a result of the introduction of 

 antibiotics, one must consider the remark- 



able role played by these agents in the treat- 

 ment of infectious diseases in animals. 

 Brucellosis and mastitis in cattle and numer- 

 ous infectious diseases of dogs, cats, poultry, 

 and other domesticated animals can now be 

 controlled by antibiotics. 



Animal Nutrition 



In addition to their use for the control of 

 infectious diseases, antibiotics have also 

 been employed extensively in the mitrition 

 of nonherbivorous animals, such as poultry 

 and swine. This effect is particularly marked 

 in animals deprived of iS-carotene and vita- 

 min A (Guerrant, 1960). For further details, 

 see Jukes (1955) and Goldberg (1959). 



Among the uses of antibiotics that invf)lve 

 both animal feeding and disease control, one 

 might mention the control of silkworm dis- 

 eases by the soaking of mulberry leaves in 

 antibiotic solutions. The use of streptomycin 

 and tetracyclines resulted not only in the 

 almost complete suppression of bacterial in- 

 fections in silkworms, but also resulted in 

 a higher finality silk (Afrikian, 1960). 



Food Pre-servation 



In recent years, certain antibiotics, nota- 

 bly the tetracyclines, which are readily de- 

 stroyed on boiling, have been used exten- 

 sively in the preservation of fish and poultry 

 products (Carey, 1958). 



Laboratory Uses 



Numerous laboratory processes have bene- 

 fited greatly from the utilization of anti- 

 biotics. One might mention their use in the 

 preparation of selective culture media for 

 the isolation of (1) gram-negative bacteria, 

 (2) anaerobic bacteria, (3) fungi, (4) proto- 

 zoa, and (5) viruses. They are used in genet- 

 ics for the isolation of special nongrowing 

 variants which depend upon specific growth 

 factors. They are used for preservation of 

 cattle semen and virus preparations. Finally, 

 their use in tissue cultures and in the produc- 



