Detection of Linezolid-Resistant and Isolates from the Layer Operation System in Korea.

Linezolid (LNZ) is one of the most important antimicrobial agents against infections caused by gram-positive bacteria, including enterococci. In a layer operation system, antimicrobial resistance can be transferred to commercial layers via the fecal-oral route. This study investigated the presence and distribution of LNZ-resistant and in a layer operation system. Among 117 and 154 , 10 (8.5%) and 5 (3.2%) isolates showed resistance to LNZ and chloramphenicol, and they exhibited multidrug resistance against 5 or more classes of antimicrobial agents. Among the resistant isolates, 9 (90.0%) and 2 (20.0%) harbored and genes, respectively. The and genes were not detected in five LNZ-resistant . None of the 15 LNZ-resistant isolates harbored the gene, and no mutations were observed in the genes encoding domain V of 23S ribosomal RNA (rRNA) and ribosomal proteins L3 () and L4 (). Transferability was identified in three of the nine -positive LNZ-resistant isolates. The , , and genes were cotransferred with the gene in all -positive transconjugants. The results indicate that is well-distributed in , implying a greater level of transferability. Thus, enhanced surveillance efforts are needed to monitor the emergence and spread of in enterococci in layer operation system.