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Tuyển tập các báo cáo nghiên cứu về bệnh thú y được đăng trên tạp chí y học General Psychiatry cung cấp cho các bạn kiến thức về ngành y đề tài: Regulation of the erm(C) Gene in Staphylococci from Reservoir with Different Usage of Macrolides. | Acta vet. scand. 2005 46 163-166. Brief Communication Regulation of the erm C Gene in Staphylococci from Reservoir with Different Usage of Macrolides By Lars B. Jensen and Frank. M. Aarestrup Danish Institute for Food and Veterinary Research Bulowsvej 27 DK-1790 Copenhagen V Denmark. A high prevalence of macrolide resistant isolates has been found among staphylococci isolated from animals 4 . The erm C gene is the most common gene encoding macrolide resistance in staphylococci 8 . It is well known that expression of the erm C gene is normally regulated by formation of hairpin structures upstream for the erm C gene 5 9 rendering the start codon of erm C gene non-accessible. Only 14- and 15-membered macrolides like erythromycin can induce expression of the gene and induce resistance while 16-membered macrolides cannot activate expression of erm C 7 . If deletions from 16 to 116 bp occur in the regulatory area expression of the erm C gene becomes constitutive 10 . Constitutive expressed erm C genes give resistance not only to 14-and 15-membered macrolides like erythromycin but also to 16-membered macrolides like spiramycin tylosin and streptogramin B 6 . Deletions are believed to be the result of high concentration of non-inducible macrolides like tylosin in the environment selecting for constitutive expression of the macrolide resistance. In the presence of macrolides like ty-losin this could give staphylococci with constitutive expressed erm C a selective advantage not only to sensitive staphylococci but also to staphylococci containing regulated erm C genes. In this article we have investigated the ratio of regulated and constitutive expressed erm C genes in human and animal reservoirs cattle and pigs with differences in uses of the 16-membered macrolide tylosin. Large amounts of the macrolide tylosin have been used for pig production in Denmark for growth promotion and therapy 1 . In 1996 68 350 kg of tylosin was used for growth promotion and 1 350 kg for therapy.
