Figure 4

Transcript levels of the adeA and adeB genes in different strains of A. baumannii . AB1026, AB1027, and AB1028 are the baeR deletion mutant, baeR reconstitution, and wild-type with baeR overexpression strains, respectively. ABTcm is the baeR deletion mutant of ABtc, which was a laboratory-induced tigecycline-resistant strain. The relative expression of adeB, adeA1, and adeA2 was determined by qRT-PCR. (A) The expression levels of adeB, adeA1, and adeA2 in AB1028 were approximately 2.9-, 2.1-, and 3-fold higher, respectively, than those in ATCC 17978, while the deletion of baeR in the wild-type strain decreased the expression levels of these three pump genes by 68.3%, 67.3%, and 73.5%, respectively. The decreased expression of the pump genes can be partially restored by baeR reconstitution. (B) The expression levels of adeB, adeA1, and adeA2 in ABtcm were 51.5%, 42.7%, and 43.7% lower, respectively, than those in ABtc. 16S rRNA gene was used as a control. The results are displayed as the means ± SD from three independent experiments. *, P < 0.05; ***, P < 0.001. #, P < 0.05 between ABtc and ABtcm.