Assessment of lung damage in DBA/2 lung following infection with <i>S. maltophilia</i>.

<p>Lung damage was macroscopically and histologically assessed in DBA/2 mice (n = 18) on days 1, 3, and 7 p.e. to <i>S. maltophilia</i> (Sm111 CF strain, red line; C39 environmental strain, green line), or PBS only (control; black line). A–C) Macroscopic examination. A) Photographs of control and infected mouse lungs are representative for lung damage observed at each time point (days 1, 3, and 7 p.e.) in 8 mice per group. C) Lung damage was assessed by using “four-point scoring system” <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0088769#pone.0088769-Johansen1" target="_blank">[24]</a>, and results are shown as median values. B–D) Histological assessment. B) Lung sections were stained with hematoxylin-eosin and ten fields/lung were observed at low (10×), and high (63×) magnification. For each group, only one representative microscopic field was reported. Since there were no significant differences in the degree of inflammation at any of the time point when evaluating the left and the right lung separately, the data were pooled and considered representative for both lungs. Mean percentage of tissue area characterized by the presence of neutrophilic infiltrate: 60% (Sm111-infected mice) vs 20% (C39-infected mice) (p<0.001, chi-square test.). D) Lung damage was quantified by using the “five-point scoring system” <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0088769#pone.0088769-Dubin1" target="_blank">[25]</a>, and results are shown as median histopatological index. *** p<0.001, ** p<0.01, * p<0.05 vs ctrl; °° p<0.01, ° p<0.05 Sm111 vs C39; Kruskall-Wallis followed by Dunn's multiple comparison <i>post-hoc</i> test.