Research Papers: Pathology:
Riemerella anatipestifer M949_0459 gene is responsible for the bacterial resistance to tigecycline
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Tao Li1, Min Shan1,2, Jing He1, Xiaolan Wang1, Shaohui Wang1, Mingxing Tian1, Jingjing Qi1, Tingrong Luo2, Yonghong Shi1, Chan Ding1 and Shengqing Yu1
1 Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, China
2 College of Animal Science and Technology, Guangxi University, Guangxi, China
Shengqing Yu, email:
Keywords: Riemerella anatipestifer, M949_0459 gene, MIC, tigecycline, resistance, Pathology Section
Received: May 16, 2017 Accepted: June 29, 2017 Published: July 27, 2017
Based on its important role in last-line therapeutics against multidrug-resistant bacteria, tigecycline has been increasingly important in treating infections. However, mounting reports on tigecycline-resistant bacterial strains isolated from different sources are of concern, and molecular mechanisms regarding tigecycline resistance are poorly understood. Riemerella anatipestifer is a Gram-negative, non-motile, non-spore-forming, rod-shaped bacterium, which causes fibrinous pericarditis, perihepatitis, and meningitis in infected ducks. We previously constructed a random transposon mutant library using Riemerella anatipestifer strain CH3, in present study, we described that Riemerella anatipestifer M949_0459 gene is responsible for the bacterial resistance to tigecycline. Using the minimum inhibitory concentration assay, a mutant strain showed significantly increased (about six-fold) tigecycline susceptibility. Subsequently, the knocked-down gene was identified as M949_0459, a putative flavin adenine dinucleotide-dependent oxidoreductase. To confirm the resistance function, M949_0459 gene was overexpressed in Escherichia coli strain BL21, and the minimum inhibitory concentration analysis showed that the gene product conferred resistance to tigecycline. Additionally, expression of the M949_0459 gene under treatment with tigecycline was measured with quantitative real-time PCR. Results showed that the mRNA expression of M949_0459 gene was elevated under tigecycline treatment with dose range of 1-10 mg/L, and peaked at 4 mg/L. Moreover, two kinds of efflux pump inhibitors, carbonyl cyanide m-chlorophenyl hydrazone and phenylalanine arginyl β-naphthylamide were tested, which showed no function on tigecycline resistance in the strain CH3. Our results may provide insights into molecular mechanisms for chemotherapy in combating Riemerella anatipestifer infections.
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