Binding of azole antibiotics to Staphylococcus aureus flavohemoglobin increases intracellular oxidative stress.
In this work, we report that flavohemoglobin contributes to the azole susceptibility of Staphylococcus aureus. We first observed that deletion of the flavohemoglobin gene leads to an increase in the viability of imidazole-treated S. aureus cells and that reversion to the wild-type phenotype occurs upon expression of flavohemoglobin from a multicopy plasmid. Further spectroscopic analyses showed that miconazole, the most efficient azole antibiotic against S. aureus, ligates to heme of both oxidized and reduced flavohemoglobin. The binding of miconazole to oxidized flavohemoglobin, with an association constant of 1.7 x 10(6) M(-1), typical of a tight, specific binding equilibrium, results in augmentation of the superoxide production by the enzyme. These results are corroborated by in vivo studies showing that imidazole-treated S. aureus cells expressing flavohemoglobin contain a larger amount of reactive oxygen species. Moreover, it was observed that the survival of miconazole-treated S. aureus internalized by murine macrophages is higher for cells lacking flavohemoglobin. Altogether, the present data revealed that in S. aureus, flavohemoglobin enhances the antimicrobial activity of imidazoles via an increase of intracellular oxidative stress.
Nobre
Lígia S
LS
Instituto de Tecnologia Química e Biológica, Universidade Nova de Lisboa, Av. da República (EAN), 2780-157 Oeiras, Portugal.
Todorovic
Smilja
S
Tavares
Ana Filipa N
AF
Oldfield
Eric
E
Hildebrandt
Peter
P
Teixeira
Miguel
M
Saraiva
Lígia M
LM
D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001393:Azoles / Q000494:pharmacology*; D001426:Bacterial Proteins / Q000378:metabolism*; D006420:Hemeproteins / Q000378:metabolism*; D008264:Macrophages / Q000382:microbiology; D051379:Mice; D018384:Oxidative Stress / Q000187:drug effects*; D017382:Reactive Oxygen Species; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000378:metabolism*
D000900:Anti-Bacterial Agents; D001393:Azoles; D001426:Bacterial Proteins; D006420:Hemeproteins; D017382:Reactive Oxygen Species; C086193:flavohemoprotein, Bacteria