Table 4.

Overexpression of marA and soxS in clinical fluoroquiolone-resistant E. coli strains with identical mutations in the regions determining quinolone resistance in gyrA and parC 

StrainaOfloxacin MIC (μg/ml)Cyclohexane tolerancebMutation inc:Overexpression ofmarAOverexpression of soxS
gyrA at amino acid:parC at amino acid:
Ser83Asp87Ser80Glu84
E58LeuAsnLys
E10d 64LeuAsnLys
NH18LeuGlyIle
HO1732+LeuGlyIle+
HO128LeuAsnIle
HO13d 32LeuAsnIle
E732+LeuAsnIle
HO9932+LeuAsnIle+
E364+LeuAsnIle+
E1964+LeuAsnIle+
E2264+LeuAsnIle+
  • a The strains, including HO strains, are genotypically unrelated (32), and they are all bloodstream isolates except for NH1, which is a urinary tract isolate.

  • b Cyclohexane tolerance of strains was tested on LB agar overlaid by the organic solvent and grown for 24 h at 30°C (33).

  • c See reference 10.

  • d Increased fluoroquinolone resistance not associated with cyclohexane tolerance.