Table 2

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

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

-

2a, b

1e

1a

0


norC

-

-

4.92 ± 0.00

5.89 ± 0.71

4.99 ± 1.51

-

0

1e

1a

0


mepA

-

-

8.59 ± 0.59

3.90 ± 0.13

5.94 ± 1.02

-

0

1f

1a

0


mdeA

-

4.97 ± 0.68

-

3.96 ± 2.10

-

4.15 ± 1.12

1c

0

0

1d


smr

n.a.

n.a.

-

n.a.

n.a.

7.66 ± 3.66

0

1f


* 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.

Costa et al. BMC Microbiology 2011 11:241   doi:10.1186/1471-2180-11-241

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