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Table 2 EP gene expression analysis by RT-qPCR of representative S. aureus exposed to CIP or EtBr.

From: Exploring the contribution of efflux on the resistance to fluoroquinolones in clinical isolates of Staphylococcus aureus

  Overexpression levels* and no. of isolates** showing gene overexpression
  ½ CIP MIC ½ EtBr MIC
   EtBrCW- EtBrCW+   EtBrCW- EtBrCW+
Gene ATCC25923 isolates isolates ATCC25923 isolates isolates
   (n = 4) (n = 6)   (n = 4) (n = 6)
norA - - - 4.51 ± 0.77 - -
   0 0   0 0
norB 13.80 ± 6.50 5.43 ± 2.39 5.47 ± 0.19 7.07 ± 2.78 5.33 ± 0.73 -
   2 a, b 1 e   1 a 0
norC - - 4.92 ± 0.00 5.89 ± 0.71 4.99 ± 1.51 -
   0 1 e   1 a 0
mepA - - 8.59 ± 0.59 3.90 ± 0.13 5.94 ± 1.02 -
   0 1 f   1 a 0
mdeA - 4.97 ± 0.68 - 3.96 ± 2.10 - 4.15 ± 1.12
   1 c 0   0 1 d
smr n.a. n.a. - n.a. n.a. 7.66 ± 3.66
    0    1 f
  1. * Gene expression was measured in the presence of ciprofloxacin and EtBr relatively to the drug-free condition. The results are expressed in terms of the mean ± standard deviation of at least three independent assays performed with independently extracted RNAs and correspond to the range of values obtained for isolates showing overexpression of that gene. **The numbers in bold correspond to the number of isolates overexpressing that gene: a isolate SM2; b SM3; c SM5; dSM25; e SM50; f SM52. Overexpression was considered for values ≥4 [10]. (-): no overexpression was detected; n.a.: not applicable.