TABLE 2.

Multipassage resistance selection results

StrainAntibacterialInitial MIC (μg/ml)Passage at which resistancea emergesFinal MIC (μg/ml) at passage 55
S. aureus NRS123 (USA400; MRSA)XF-730.5No resistance1
Vancomycin1No resistance4
Retapamulin0.2538
Fusidic acid0.125256
Mupirocin0.12732
S. aureus NRS382 (USA100; MRSA)XF-730.25No resistance1
Vancomycin132 (35b)8
Retapamulin0.259 (13b)8
Fusidic acid0.122256
Mupirocin0.12216
S. aureus NRS384 (USA300; MRSA)XF-730.25No resistance0.5
Vancomycin120 (46b)8
Daptomycin0.5532
Retapamulin0.2516 (19b)4
Fusidic acid0.122256
Mupirocin0.122512
S. aureus NRS387 (USA800; MRSA)XF-730.25No resistance0.5
Vancomycin1No resistance4
Retapamulin0.25158
Fusidic acid0.121256
Mupirocin0.122256
  • a Resistance is defined as >4-fold increase in original MIC (4, 7, 21).

  • b Passage number at which three successive elevated MICs were first obtained.