| Summary: | 碩士 === 國立陽明大學 === 醫學生物技術研究所 === 92 === Abstract
We previously generated transposon insertion mutant which derived from a ceftriaxone(CRO)-resistant strain of Salmonella enterica serovar Typhimurium WT200. Mutant 6B7 and 8F9 are transporter genes yjeH and ydgF which truncated by transposon insertion, respectively, and both have 4-fold reduction of CRO resistance. To elucidate whether these two genes correlated with CRO resistance, we constructed the expression vectors pBAD-yjeH-DsRed and pBAD-ydgFE-DsRed which carry functional yjeH and ydgFE genes, respectively, for the complementation test. The ydgFE is composed of two genes ydgF and ydgE in the same operon. The MICs of mutant 6B7 strain with pBAD-yjeH-DsRed against CRO increased to the same level of WT200. This result indicated overexpression of YjeH can completely restore CRO resistance in 6B7 mutant strain. WT200 strain with or without pBAD-yjeH-DsRed were tested against CRO in the presence of CCCP, an energy uncoupler that has been shown to inhibit the action of efflux pumps. The MICs of WT200 strain with YjeH overexpression are higher than those of bacteria without YjeH overexpression. This is the additional evidence to suggest that YjeH transporter protein can confer CRO resistance in Salmonella typhimurium. Since YjeH is a putative transporter, which belongs to APA family, and was never reported to correlate with drug resistance. In this study, it is the first time to prove that the member of APA family is associated with drug resistance . Further studies are needed to prove whether CRO is the substrate of this transporter. We were also able to demonstrate ydgEF genes are correlated with CRO resistance in Salmonella typhimurium by the complementation test. Since YdgEF is a putative cation transporter which belongs to small drug resistance family of efflux pump system, we will perform more studies to prove how ydgEF can confer CRO resistance in the near future.
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