AUTHOR=Zhu De-Kang , Luo Hong-Yan , Liu Ma-Feng , Zhao Xin-Xin , Jia Ren-Yong , Chen Shun , Sun Kun-Feng , Yang Qiao , Wu Ying , Chen Xiao-Yue , Cheng An-Chun , Wang Ming-Shu 

TITLE=Various Profiles of tet Genes Addition to tet(X) in Riemerella anatipestifer Isolates From Ducks in China

JOURNAL=Frontiers in Microbiology

VOLUME=9

YEAR=2018

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2018.00585

DOI=10.3389/fmicb.2018.00585

ISSN=1664-302X

ABSTRACT=<p>To investigate tetracycline resistance and resistant genotype in <italic>Riemerella anatipestifer</italic>, the tetracycline susceptibility of 212 <italic>R. anatipestifer</italic> isolates from China between 2011 and 2017 was tested. The results showed that 192 of 212 (90.6%) <italic>R. anatipestifer</italic> isolates exhibited resistance to tetracycline (the MICs ranged from 4 to 256 μg/ml). The results of PCR detection showed that, 170 of 212 (80.2%) <italic>R. anatipestifer</italic> isolates possessed the <italic>tet</italic>(X) gene. Other genes, including <italic>tet</italic>(A), <italic>tet</italic>(M), <italic>tet</italic>(Q), <italic>tet</italic>(O), <italic>tet</italic>(B), and <italic>tet</italic>(O/W/32/O), were found at frequencies of 20.8, 4.7, 1.4, 0.9, 0.9, and 0.5%, respectively. However, <italic>tet</italic>(C), <italic>tet</italic>(E), <italic>tet</italic>(G), <italic>tet</italic>(K), and <italic>tet</italic>(W) were not detected in any isolate. In these <italic>tet</italic> gene positive strains, 31 (14.6%), 2 (0.9%), 5 (2.4%), 1 (0.5%), 3 (1.4%) were detected containing <italic>tet</italic>(A)/<italic>tet</italic>(X), <italic>tet</italic>(M)/<italic>tet</italic>(O), <italic>tet</italic>(M)/<italic>tet</italic>(X), <italic>tet</italic>(O)/<italic>tet</italic>(X), and <italic>tet</italic>(Q)/<italic>tet</italic>(X) simultaneously, respectively. One isolates, R131, unexpectedly contained three <italic>tet</italic> genes, i.e., <italic>tet</italic>(M), <italic>tet</italic>(O), and <italic>tet</italic>(X). Sequence analysis of the <italic>tet</italic> gene ORFs cloned from <italic>R. anatipestifer</italic> isolates confirmed that <italic>tet</italic>(A), <italic>tet</italic>(B), <italic>tet</italic>(M), <italic>tet</italic>(O), <italic>tet</italic>(Q) and an unusual mosaic <italic>tet</italic> gene <italic>tet</italic>(O/W/32/O) were present in <italic>R. anatipestifer</italic>. The MIC results of <italic>R. anatipestifer</italic> ATCC 11845 transconjugants carrying <italic>tet</italic>(A), <italic>tet</italic>(B), <italic>tet</italic>(M), <italic>tet</italic>(O), <italic>tet</italic>(O/W/32/O), <italic>tet</italic>(Q), and <italic>tet</italic>(X) genes exhibited tetracycline resistance with MIC values ranging from 4 to 64 μg/ml. Additionally, the <italic>tet</italic>(X) gene could transfer into susceptible strain via natural transformation (transformation frequencies of ~10<sup>−6</sup>). In conclusion, the <italic>tet</italic>(A), <italic>tet</italic>(B), <italic>tet</italic>(M), <italic>tet</italic>(O), <italic>tet</italic>(O/W/32/O), <italic>tet</italic>(Q), and <italic>tet</italic>(X) genes were found and conferred tetracycline resistance in <italic>R. anatipestifer</italic> isolates. Moreover, the <italic>tet</italic>(X) is the main mechanism of tetracycline resistance in <italic>R. anatipestifer</italic> isolates. To our knowledge, this is the first report of <italic>tet</italic>(A), <italic>tet</italic>(B), <italic>tet</italic>(M), <italic>tet</italic>(O), <italic>tet</italic>(Q), and mosaic gene <italic>tet</italic>(O/W/32/O) in <italic>R. anatipestifer</italic>.</p>