Research article
Immunization protected well nourished mice but not undernourished ones from lung injury in Methicillin-resistant Staphylococcus aureus (MRSA) infection
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* Corresponding author: Alexandrina Sartori sartori@ibb.unesp.br
Department of Microbiology and Immunology, Institute of Biosciencies, São Paulo State University (UNESP), Botucatu, Brazil, Distrito de Rubião Junior s/n, CEP: 18.618-000
BMC Microbiology 2009, 9:240 doi:10.1186/1471-2180-9-240
Published: 23 November 2009Abstract
Background
Staphylococcus aureus methicillin-resistant (MRSA) has been frequently isolated from endotracheal and lung puncture aspirates in malnourished children with pneumonia. In this work we evaluated the susceptibility of undernourished BALB/c mice and its ability to mount a protective immunity against MRSA with emphasis on the lung involvement.
Results
BALB/c mice submitted to a 20% dietary restriction during 20 days presented a significant decrease in body weight, lymphocyte number and also atrophy in thymus and intestinal epithelium. Determination of bacterial load by the number of colony forming units (CFU) indicated a similar susceptibility whereas the findings of Gram stain clearly suggested a higher amount of bacteria in the lungs of normal mice than in the undernourished ones. Immunization reduced bacterial growth in the lungs of normal mice but not in the undernourished ones. Histopathological analysis showed that inflammation appeared in the lungs from normal mice only after infection and that immunization prevented this pulmonary inflammatory process. On the other hand, undernourished mice presented lung inflammation even before infection. In addition, the degree of this inflammatory process did not change with infection or previous immunization.
Conclusion
Our results indicated that lung injury during MRSA infection is prevented by previous immunization in well nourished but not in undernourished mice.