Bacterial loads at injection site and in draining lymph node.

<p>Data are means of log₁₀ of cfu numbers recovered from 77 mice infected over six independent experiments. Bars = Standard Errors. Stars indicate that the data are significantly different between the two <i>Yersinia</i> species (p≤0.0001). The dashed line shows the detection limit (10 cfu). The cross symbol indicates that most <i>Y. pestis</i>-infected mice died between days 2 and 3.</p

Draining lymph node gross pathology.

<p>Macroscopical aspect of lymph nodes two days after inoculation of either saline, ∼5500 <i>Y. pseudotuberculosis</i> cfu or ∼5500 <i>Y. pestis</i> cfu. Lymph node from <i>Y. pseudotuberculosis</i>-infected mice is purulent whereas <i>Y. pestis</i>-infected lymph node is reddish and adherent to neighboring tissues. Bar = 2 mm.</p

Examples of the three histopathological types of the draining lymph nodes.

<p>Lymph nodes were taken 24 h (type 1) and 72 h (type 2 and 3) after inoculation of ∼4500 cfu of <i>Y. pseudotuberculosis</i> (types 1 and 2) or <i>Y. pestis</i> (type 3). Sections were stained by Hematoxylin-Eosin (HE), and by antibodies specific to <i>Y. pseudotuberculosis</i> or to <i>Y. pestis</i> (Bact), to PMNs and to B lymphocytes (BL). Immunostainings give a brownish color. Arrowheads on the HE-stained sections indicate the border of the inflammatory front. Bacteria (arrows) are present as tiny bacterial foci at the periphery (type 1), well delimited patches (type 2) or flame-like formations (type 3). The BL staining shows that the overall structure of the type 1, but not of the type 3, lymph node is preserved, while, in the type 2 lymph node, the inflammatory reaction forced B lymphocytes to the central part of the organ. Bar = 100 µm.</p

Criteria used to score sections of lymph nodes infected with <i>Y. pestis</i> or <i>Y. pseudotuberculosis</i>, and their discriminating indexes.

<p>Discriminating indexes are the test values in the right column. Only significant test values (i.e. >1.96 or <−1.96) are given. Positive and negative test-values are distinctive of, respectively, <i>Y. pestis</i> and <i>Y. pseudotuberculosis</i> infections.</p

Dendrogram of the draining lymph node histopathological profiles.

<p>Each label indicates (in order): infecting species (P for <i>Y. pestis</i>, T for <i>Y. pseudotuberculosis</i>), delay between mouse infection and lymph node collection (in days), amount of injected cfu. Top scale = % similarity</p

Illustrations of some of the criteria used for scoring.

<p>Panels A–E, G, H and J–L display HE stained sections, panels F and I show sections immunostained with <i>Y. pestis</i> specific antibodies. In the text below, the criteria are referred to according to the numbering in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0001688#pone-0001688-t001" target="_blank">Table 1</a>. A: Wedge shaped abscess (criterion 4) indicated by arrows. Within the abscess bacterial colonies are visible as pink patches. B: Peripheral layer of PMNs containing bacterial foci (criterion 9), with a blunt demarcation (arrows) from the lymph node tissue (criterion 11). Inset: higher magnification to show the characteristic horseshoe shaped nuclei of the PMNs, and a bacterial focus. C: Layer of PMNs bordering a peripheral band of bacteria, cell debris and PMNs (criterion 10). The inset shows the typical PMN morphology of the cells within the layer. Behind this layer, bacterial aggregates are seen as pink areas (arrowheads) containing purple dots that are, as seen as higher magnification (not shown here) PMNs and cell debris. D: Patch of densely packed bacteria, bordered by PMNs (criterion14). Packed bacteria form a pink 8-shaped area at the centre of the picture (star). E: Atypical bacterial patch (criterion 15). At the center of the picture an aggregate of bacterial rods, not as densely packed as the preceding one, is loosely surrounded by inflammatory cells. F: A large bacterial zone (criterion 17), stained brownish on the preparation. G: Isolated host cells within a bacterial zone (criterion 19). Isolated host cells and cell remnants are seen amid a sea of bacteria which gives a “ground glass” appearance to this part of the LN section. H, <i>left</i>: bacterial infiltration around host cells (criterion 20). A bacterial strand (arrow), that seems to originate from a nearby colony (star), passes between host cells. H, <i>right</i>: Free floating bacterium, indicated by an arrow (criterion 21). I: Zone of reduced tissular density (arrows) outside bacterial areas, which are brownish on this preparation (criterion 26). This image also shows flame-like inward bacterial projections (criterion 18). J: Area of reduced host cell density with a reticular pattern (criterion 27) and containing numerous pycnotic cells (criterion 32). K: Moth eaten appearance (criterion 33) of a lymph node with areas of contrasting tissular densities. L: Vascular congestion (criterion 40), showing bright red on this preparation. <i>Magnifications</i>: Panels A–C, F, I–L : bar = 200 µm. Insets of panels B and C: bar = 50 µm. Panels D, E, G and H: bar = 10 µm.</p

Bacteriophage P3-CHA cure and prevent lung infections caused by a clinical <i>P. aeruginosa</i> strain.

<p>(<b>A–B</b>) Survival curves of mice infected with the CHA strain and treated or pre-treated with P3-CHA bacteriophage. (<b>A</b>) PBS (♦), 3×10⁶ (•) and 3×10⁷ (□) pfu of bacteriophage were given intranasally 2 h after bacteria (3×10⁶ cfu) were administered. This curative treatment appears to be dose dependent (P<0.0001 for both bacteriophage doses compared to PBS and P<0.01 between 3×10⁶ and 3×10⁷ bacteriophage doses). (<b>B</b>) Four days before infection with 3×10⁶ bacteria, mice were given either 3×10⁷ (•), or 3×10⁸ (□) pfu of P3-CHA or 3×10⁸ pfu of heat-inactivated P3-CHA solution (♦). These survival curves indicate that the preventative treatment is dose dependent (P<0.0005 and P<0.0001 for 3×10⁷ and 3×10⁸ bacteriophage doses respectively compared to heat-inactivated bacteriophage solution and P<0.0005 between 3×10⁷ and 3×10⁸ bacteriophage doses). (<b>C–D</b>) 20 h after infection with strain CHA, mice were euthanized and BAL fluids were assayed for bacteria (<b>C</b>) and bacteriophages (<b>D</b>). In the curative treatment protocols, mice were treated with PBS or bacteriophage 2 h post infection (phage 2 h pi). In the preventative treatment protocols, mice were intranasally administered bacteriophage solution (4d phage) or heat-inactivated bacteriophage solution (4d phage 80°C) four days before infection. (<b>C</b>) Bacterial counts were significantly lower in the BAL fluids from mice that had received either curative or preventative bacteriophage treatment than the respective control treatment (* P<0.05, and ** P<0.01). (<b>D</b>) Bacteriophage counts were significantly lower in the BAL fluids from mice that had received bacteriophage treatment than the non-infected animals (** P<0.01) or the non-infected animals pre-treated four days earlier with the bacteriophage P3-CHA (* P<0.05).</p

Characterization of PAK-P3 and P3-CHA bacteriophages.

<p>(<b>A</b>, <b>C</b>) Electron micrographs of PAK-P3 (<b>A</b>) and P3-CHA (<b>C</b>). Scale bar: 100 nm. (<b>B</b>) SDS-PAGE of PAK-P3 and P3-CHA proteins; only the most abundant proteins give visible signals (MW: molecular weight markers, the arrow points to the major capsid proteins). (<b>D</b>) Clustal alignment of the three major capsid proteins of PAK-P1, PAK-P3 and P3-CHA bacteriophages with their closest homologs in the database with known function (the major capsid protein of Felix 01 bacteriophage; NP_944891). Major capsid proteins of PAK-P3 and P3-CHA are 100% identical.</p

Persistence of P3-CHA bacteriophage in lungs of uninfected mice.

<p>Three groups of five mice were given 3×10⁸ pfu of bacteriophage P3-CHA, administered intranasally. The number of bacteriophages in BAL fluids was determined 1, 4 and 5 days post-administration (n = 5).</p

Survival curve of infected mice treated with bacteriophage PAK-P3 compared to P3-CHA.

<p>Mice were infected intranasally with 3×10⁶ cfu (CHA strain) and 2 h later were treated with either PBS (♦) or 3×10⁷ pfu of bacteriophage PAK-P3 (•), or 3×10⁷ pfu of bacteriophage P3-CHA (□) also administered intranasally (P<0.005 for both P3-CHA and PAK-P3 bacteriophage doses compared to PBS and P<0.05 between P3-CHA and PAK-P3 bacteriophage doses).</p