TABLE 4.

Influence of plasmid-expressed PA5471 on norfloxacin resistance in P. aeruginosa

StrainRelevant propertyMIC (μg/ml) of norfloxacina
−Mg2++Mg2+
YM34(pUCP20T)bMexXY+0.252
YM34(pYM010)MexXY+ PA5471++c0.58
YM44(pUCP20T)MexXY0.120.25
YM44(pYM010)MexXY PA5471++c0.120.25
  • a Norfloxacin MICs were determined in the presence and absence of 5 mM MgCl2. Mg2+ enhances MexXY-mediated antimicrobial resistance, possibly by enhancing the activity of this efflux system (28).

  • b Lacks MexAB-OprM, MexCD-OprJ, and MexEF-OprN.

  • c PA5471 was overexpressed from plasmid pYM010.