Open AccessInfluence of Subtherapeutic Levels of Oxytetracycline on Salmonella typhimurium in Swine, Calves, and Chickens
Author(s) -
D. G. Evangelisti,
Arthur R. English,
Arthur E. Girard,
John E. Lynch,
I. A. Solomons
Publication year - 1975
Publication title -
antimicrobial agents and chemotherapy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.07
H-Index - 259
eISSN - 1070-6283
pISSN - 0066-4804
DOI - 10.1128/aac.8.6.664
Subject(s) - oxytetracycline , biology , salmonella , feces , veterinary medicine , antibiotics , streptomycin , inoculation , population , incidence (geometry) , microbiology and biotechnology , broiler , zoology , bacteria , medicine , immunology , genetics , physics , environmental health , optics
Subtherapeutic levels of oxytetracycline in animal feeds have been evaluated to determine their influence on the relative quantity, prevalence, shedding, and antibiotic susceptibility ofSalmonella typhimurium in swine, calves, and chickens, when compared with nonmedicated controls. The medicated groups were fed rations containing oxytetracycline commencing 5 days prior to oral inoculation withS. typhimurium and continuing through a 28-day post-inoculation period. Colonization ofS. typhimurium occurred in all three animal species as evidenced by clinical signs of infection and/or colony counts in feces measured on seven separate occasions over the 28-day observation period. The accumulated data demonstrate that the subtherapeutic use of oxytetracycline did not bring about any increases in the quantity, prevalence, or shedding ofS. typhimurium in swine, calves, and chickens. In fact, the medication generally brought about a decrease in the percentage of animals carryingS. typhimurium during the study period. In contrast to results in swine and calves, there was a significant occurrence ofS. typhimurium resistance to oxytetracycline in chickens. Resistant colonies were isolated from chickens sporadically but never on more than two consecutive test periods. These isolates were also resistant to streptomycin, but not to the other six antibiotics tested. The population of resistantS. typhimurium isolated from medicated chickens was no larger than that of susceptibleS. typhimurium isolated from the nonmedicated animals. It is concluded that no evidence has been obtained which would relate the continuous low-level feeding of oxytetracycline for a 4-week period to an increased incidence of disease in animals or as a hazard to humans.