Investigation of the potential for mutational resistance to XF-73, retapamulin, mupirocin, fusidic acid, daptomycin, and vancomycin in methicillin-resistant Staphylococcus aureus isolates during a 55-passage study

Antimicrob Agents Chemother. 2011 Mar;55(3):1177-81. doi: 10.1128/AAC.01285-10. Epub 2010 Dec 13.

Abstract

XF-73 is a dicationic porphyrin drug with rapid Gram-positive antibacterial activity currently undergoing clinical trials for the nasal decolonization of Staphylococcus aureus, including methicillin-resistant Staphylococcus aureus (MRSA). In multistep (55-passage) resistance selection studies in the presence of subinhibitory concentrations of XF-73, retapamulin, mupirocin, fusidic acid, and vancomycin against four Network on Antimicrobial Resistance in Staphylococcus aureus MRSA strains, there was no >4-fold increase in the MIC for XF-73 after 55 passages. In contrast, there was an increase in the MICs for retapamulin (from 0.25 μg/ml to 4 to 8 μg/ml), for mupirocin (from 0.12 μg/ml to 16 to 512 μg/ml), for fusidic acid (from 0.12 μg/ml to 256 μg/ml), and for vancomycin (from 1 μg/ml to 8 μg/ml in two of the four strains tested). Further investigations using S. aureus NRS384 (USA300) and daptomycin demonstrated a 64-fold increase in the MIC after 55 passages (from 0.5 μg/ml to 32 μg/ml) with a >4-fold increase in the MIC obtained after only five passages. Sequencing analysis of selected isolates confirmed previously reported point mutations associated with daptomycin resistance. No cross-resistance to XF-73 was observed with the daptomycin-resistant strains, suggesting that whereas the two drugs act on the bacterial cell membrane, their specific site of action differs. XF-73 thus represents the first in a new class of antibacterial drugs, which (unlike the comparator antibiotics) after 55 passages exhibited a ≤4-fold increase in MIC against the strains tested. Antibacterial drugs with a low propensity for inducing bacterial resistance are much needed for the prevention and treatment of multidrug-resistant bacteria both within and outside the hospital setting.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Anti-Bacterial Agents / pharmacology*
  • Bridged Bicyclo Compounds, Heterocyclic / pharmacology*
  • Daptomycin / pharmacology*
  • Diterpenes
  • Fusidic Acid / pharmacology*
  • Methicillin-Resistant Staphylococcus aureus / drug effects*
  • Methicillin-Resistant Staphylococcus aureus / genetics
  • Microbial Sensitivity Tests
  • Molecular Structure
  • Mupirocin / pharmacology*
  • Polymerase Chain Reaction
  • Porphyrins / chemistry
  • Porphyrins / pharmacology*
  • Sequence Analysis, DNA
  • Vancomycin / pharmacology*

Substances

  • Anti-Bacterial Agents
  • Bridged Bicyclo Compounds, Heterocyclic
  • Diterpenes
  • Porphyrins
  • XF73 compound
  • retapamulin
  • Fusidic Acid
  • Vancomycin
  • Mupirocin
  • Daptomycin