Principle component analysis based on growth condition from Saur2A GeneChip mRNA hybridization data.

<p>Mean centering and scaling was used to transform the resulting eigenvectors into indices of explained variability. The axis scale indicates fraction of the total variance explained by the individual principle component plotted on that axis. Each point on the graph is labeled with its particular growth condition. Panel A: Principle component 1 vs. principle component 2. Panel B: Principle component 2 vs. principle component 3.</p

Changes in the <em>Staphylococcus aureus</em> Transcriptome during Early Adaptation to the Lung

<div><p><em>Staphylococcus aureus</em> is a common inhabitant of the human nasopharynx. It is also a cause of life-threatening illness, producing a potent array of virulence factors that enable survival in normally sterile sites. The transformation of <em>S. aureus</em> from commensal to pathogen is poorly understood. We analyzed <em>S. aureus</em> gene expression during adaptation to the lung using a mouse model of <em>S. aureus</em> pneumonia. Bacteria were isolated by bronchoalveolar lavage after residence in vivo for up to 6 hours. <em>S. aureus</em> in vivo RNA transcription was compared by microarray to that of shake flask grown stationary phase and early exponential phase cells. Compared to in vitro conditions, the in vivo transcriptome was dramatically altered within 30 minutes. Expression of central metabolic pathways changed significantly in response to the lung environment. Gluconeogenesis (<em>fbs</em>, <em>pckA</em>) was down regulated, as was TCA cycle and fermentation pathway gene expression. Genes associated with amino acid synthesis, RNA translation and nitrate respiration were upregulated, indicative of a highly active metabolic state during the first 6 hours in the lung. Virulence factors regulated by <em>agr</em> were down regulated in vivo and in early exponential phase compared to stationary phase cells. Over time in vivo, expression of <em>ahpCF</em>, involved in H₂O₂ scavenging, and <em>uspA</em>, which encodes a universal stress regulator, increased. Transcription of leukotoxic α and β-type phenol-soluble modulins <em>psmα1-4</em> and <em>psmβ1-2</em> increased 13 and 8-fold respectively; <em>hld</em> mRNA, encoding δ-hemolysin, was increased 9-fold. These were the only toxins to be significantly upregulated in vivo. These data provide the first complete survey of the <em>S. aureus</em> transcriptome response to the mammalian airway. The results present intriguing contrasts with previous work in other in vitro and in vivo models and provide novel insights into the adaptive and temporal response of <em>S. aureus</em> early in the pathogenesis of pneumonia.</p> </div

Matrix of significant changes in gene expression between conditions.

<p>Gene qualifiers on the microarray were considered significantly different between growth conditions if they were assigned a p<0.05 by ANOVA and also exhibited a fold change difference of greater than or equal to 2.</p

Gene tree with corresponding heat map of genes belonging to COG group J (translation).

<p>Genes were organized by average linkage clustering with distances determined by their pair-wise Pearson correlation coefficients. The scale on the left indicates transcriptional activity; classification into ribosomal protein synthesis compared to tRNAs, tRNA synthesis translation & elongation factors is depicted by brackets on the right. Columns in the heat map are labeled at the top with their corresponding growth conditions. Glycine tRNA <i>glyS</i> which had highest expression in stationary phase and translation factor <i>tuf</i> which was highly expressed under all conditions are labeled on the figure.</p

Expression of virulence regulators.

<p>Schema of the <i>S. aureus</i> virulence regulatory network based on the current understanding of the interrelationships between regulators. Transcriptional changes seen in strain JP1 during adaptation to the mouse airway are shown for each gene. Green and red lines indicate positive and negative regulation, respectively, between interacting regulators. The color scale on the left indicates transcriptional activity for each gene; a key for the gene expression by growth condition is shown on the bottom center of the figure. Transcriptional units are shown as dashed lines above or below the operons originating at their respective promoters. Where operons have multiple promoters, the regulator acting at the specific promoter is diagrammed. Osmotic pressure is indicated by the symbol π. The RNAII and III transcripts are shown as dashed lines above their respective operons.</p

Expression of <i>S. aureus</i> virulence factors in strain JP1 during growth in laboratory media and the mouse airway.

<p>The color scale on the right indicates transcriptional activity for each gene and corresponds to the key for growth conditions at the bottom right of the figure. Transcriptional units are shown as dashed lines above their respective operons.</p

Alterations in transcription grouped according to CVI CMR main role categories.

<p>Genes with changes in transcription after 30′ in vivo (compared to cells from stationary phase or growth in fresh LB) were categorized by their main role as assigned by the Craig J. Vintner Comprehensive Microbial Resource. A 2-fold or greater difference in transcription and significance p<0.05 ANOVA was required for inclusion.</p

<i>S. aureus</i> mixed acid fermentation pathways and the transcriptional activities of the respective genes under in vitro and in vivo growth conditions.

<p>Upregulated genes are labeled in red whereas down regulated genes are labeled in green. The size of the label indicates the degree of change between conditions as indicated by the key in the upper right hand corner. Panel A: Stationary phase cells vs. 30′ in the mouse airway. Panel B: Cells grown 30′ in fresh LB vs. 30′ in the mouse airway. Panel C: Stationary phase cells vs. cells grown 30′ in fresh LB.</p

Pyelonephritis/urosepsis.

<p>HICs, high-income countries.</p

Serious and Life-Threatening Pregnancy-Related Infections: Opportunities to Reduce the Global Burden

Serious and Life-Threatening Pregnancy-Related Infections: Opportunities to Reduce the Global Burde