Figure 5.

Staphylococcus aureus growth in l-lactate-rich cardiac tissue in the presence of host NO· requires Lqo. (A) Individual gluconeogenic carbon sources (e.g., 1.0% l-lactate or 1.0% tryptone) do not support NO· resistance in chemically defined medium as does 0.5% glucose. However, combining 0.1% l-lactate with 1.0% tryptone allows S. aureus to grow in the presence of NO·. NO· in the form of 10 mM DETA/NO was added once cells reach an OD₆₆₀ = 0.15 depicted here as t₀. (B) Myocardial abscesses in mice infected with WT S. aureus Newman 5 days post-inoculation. Left, hematoxylin and eosin staining of abscess reveal a central bacterial microcolony (black arrow) surrounded by infiltrating granulocytic cells. Center, immuno-histofluorescent staining of the same abscess with anti-iNOS monoclonal Ab reveals robust iNOS expression throughout the abscess. Tissue was counter-stained with DAPI to reveal host cell nuclei. Non-staining S. aureus microcolony is visible (white arrow). Right, identical immuno-histofluorescent staining of a similar abscess in an iNOS^−/− mouse as a negative control for anti-iNOS Ab. Tissue was also counter-stained with DAPI. (C) Metabolite data from murine tissues were determined using enzymatic methods previously described and normalized to total organ weight.