Abstract
Conclusions
Organisms made resistant in vitro to either tetracycline or oxytetracycline by repeated subcultures in these antibiotics developed essentially complete cross-resistance to each other and to chlortetracycline. No cross-resistance or increases in sensitivity to penicillin, streptomycin, bacitracin, polymyxin, neomycin or erythromycin developed as a result of the increases in resistance to the tetracyclines. Three strains of coliform-resistance to chloramphenicol following subcultures in either tetracycline ro oxytetracycline, but similar cross-resistance was not observed in 5gram-positive coccal strains.
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