HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Radisson, J. J. Articles by Swenson, M. J. Search for Related Content PubMed Articles by Radisson, J. J. Articles by Swenson, M. J.

The Mode of Action of Antibiotics in the Nutrition of the Dairy Calf. II. Effect of Aureomycin¹ Administered Orally to Young Dairy Calves on the Sensitivity of Intestinal Bacteria to Phagocytosis^,2

Departments of Dairy Husbandry, Bacteriology, and Veterinary Medicine Kansas Agricultural Experiment Station, Manhattan

ABSTRACT

In a preceding study, Radisson et al. (34) showed that standard bacteriological techniques alone are inadequate for determining the mode of action of certain antibiotics on the intestinal flora of young dairy calves. Also, evidence was presented that the ingestion of certain antibiotics may cause changes in the physiology of the bacteria of the intestinal tract. The most striking and consistent physiologic change is the increase in the resistance of intestinal bacteria to certain antibiotics following feeding of low levels of these antibiotics. Drug-fastness of the intestinal microorganisms has been reported by others (4, 9, 10, 11, 18, 35, 39). Such an increase in resistance of bacteria to antibiotics has been considered one of the dangers of feeding antibiotics for a long period of time. However, antibiotic-resistant organisms generally have a slower rate of metabolism and less virulence than do sensitive strains of these same organisms (33). Also, sensitive organisms have been reported to decrease in virulence after exposure to antibiotics in vitro and in vivo (7, 8, 13, 17).

¹ The trademark of American Cyanamid Co., Pearl River, N. Y., for the antibiotic chlortetracycline is Aureomycin.

² Contribution No. 242, Department of Dairy Husbandry, No. 310, Department of Bacteriology, and No. 151, Department of Veterinary Medicine, Kansas Agricultural Experiment Station, Manhattan. Supported in part by a grant from American Cyanamid Co.

Portion of a dissertation presented by the senior author as partial fulfillment of the requirements for the degree of Doctor of Philosophy in Animal Nutrition at Kansas State College.

³ Present address: c/o Duquesne S. A., Montfort (Eure), Prance.