i)mediante la tecnica de dilucion en agar. Todas las bacterias analizadas fueron sensibles a tiamulina (CM i ≤0,1 µg/ml) y lincomicina (CMI 1 µg/ml) y resistentes a tilosina (CMI 5 µg/ml). Palabras clave: Brachyspira, ponedoras comerciales, CM i, dilucion en agar, tiamulina, tilosina, lincomicina. AntiMiCroBiAl SUSCePtiBilitY teSt in Brachyspira pilosicoli StrAinS iSolAted FroM CoMMerCiAl lAYerS FArMS in ColoMBiA ABStrACt intestinal spirochaetes of the genus Brachyspira cause important diseases in swine and poul - try. an increasing problem in the presentation of resistant strains to the antimicrobial drugs usually used to treat the intestinal spirochaetosis in swine has been evidenced and this could be applicable to the isolations from poultry. There are very few reports of in vitro antimicro - bial susceptibility of Brachyspira spp. isolated from birds. in this study the antimicrobial susceptibility of twelve Brachyspira pilosicoli isolates obtain from commercial layers was evaluated against tiamulin, tylosin and lincomycin establishing the Minimum inhibitory Con - centration (MC) by agar dilution technique. all bacteria analyzed were sensitive to tiamulin (MIC ≤0,1µg/ml), and lincomycin (MIC 1µg/ml) and resistant to tylosin (MIC 5µg/ml).