This inflammatory FK506 supplier reaction clearly subsided if the animals were immunized before infection (figure 3e). However, undernourished mice presented a distinct lung involvement. They already presented a pulmonary disseminated inflammatory process before infection with S. aureus. This reaction was characterized by septal thickening and a clear mononuclear cell infiltration (figure 3b). Interestingly, the intensity and the quality of this inflammatory

reaction were not altered by infection preceded or not by immunization with killed S. aureus, as documented at figure 3d and 3f, respectively. Figure 3 Effect of dietary restriction and immunization on lung histology. BALB/c mice were submitted to dietary restriction (20%), immunized with the formolized bacteria and infected with S. aureus (5 × 108 CFU/0.5 ml). Lung sections were obtained 24 hours later, stained with H&E and analysed with a Leica microscope. Lung samples from normal (a), undernourished (b), well nourished and infected (c), undernourished and infected (d), well nourished immunized and infected (e), undernourished immunized and infected (f). Bacterial density

evaluated by Gram stain Staining of lung sections Ro 61-8048 research buy by Gram showed absence of the typical Gram positive cocci in non infected mice (figure 4a and 4b), independently of their nutritional status. A great amount of cocci was, as expected, present in infected well nourished mice Bay 11-7085 (figure 4c). Immunization of these animals before infection visibly reduced the amount of these bacteria in lung parenchyma (figure 4e). Lung evaluation in undernourished mice indicated two striking differences. Comparing to well

nourished group, the undernourished one presented a clear reduction in the amount of cocci in the lungs (figure 4d). In addition, previous immunization of these animals did not reduce lung colonization by the bacteria (figure 4f). Figure 4 Effect of dietary restriction and immunization on lung bacterial load. BALB/c mice were submitted to dietary restriction (20%), immunized with the formolized bacteria and infected with S. aureus (5 × 108 CFU/0.5 ml). Lung sections were obtained 24 hours later, stained with Gram and analysed with a Nikon microscope. Lung samples from normal (a), undernourished (b), well nourished and infected (c), undernourished and infected (d), well nourished immunized and infected (e), undernourished immunized and infected (f). Arrows indicate bacteria location. check details Discussion Protein energy malnutrition (PEM) is the most common type of undernutrition. It leads to secondary immunodeficiency and consequently increased susceptibility to infectious agents, including to S. aureus [13–15]. In this context, this work was done to establish a murine experimental model of PEM and to evaluate the effect of malnutrition on both, susceptibility and ability to mount a protective immunity against a methicillin-resistant S. aureus (MRSA).