Decreasing oxytetracycline resistance in Enterobacteriaceae in veterinary and health conditions after exchange of this substance in animal nutrition

: The national strategy for the use of chemotherapeutics under which there is a distinction between therapeutics and growth promoters for all uses (human medicine, veterinary medicine, animal nutrition) has resulted in a distinct reduction of the selection pressure and a decrease of the OTC resistance among Enterobacteriaceae in the eastern German Lander (formerly GDR) due to a reduction of OTC feeding after 1981 and the final prohibition in 1983. In the following years Enterobacteriaceae were investigated as infectious pathogens for humans and animals using antibiograms. On the one hand, the OTC resistance of porcine and bovine E. coli strains decreased only by 27% and 17%, respectively, during the 1980 to 1988 period, on the other, the OTC resistance of bovine S. typhimurium dropped by 65%, porcine S. typhimurium by 50%, bovine S. dublin by 50%, porcine S. choleraesuis by 30% to a resistance level of about 13% (1989) demonstrating a reduced pressure of resistance. At the same time, OTC resistance became diminished from 50% and 70%, respectively, to 30% also in Enterobacteriaceae (E. coli, Klebsiella) and enterococci isolated from urine and wound infections of patients in the non-agricultural population although therapeutic habits had remained unchanged. The results shown point to a spreading of resistance plasmids which has to be expected far beyond the field of OTC use, for example after the use of antibacterial growth promoters in livestock farming. Control measures should be introduced.