Journal de pathologie clinique et expérimentale

Abstrait

Mice Infection by Methicillin-Resistant Staphylococcus Aureus from Different Colonization Sites in Humans Resulting in Difusion to Multiple Organs

Silva-Santana G, Lenzi-Almeida KC, Fernandes-Santos C, Couto DS, Paes-De-Almeida EC and Aguiar-Alves F

Staphylococcus aureus is an infectious agent which can replicate in the blood, colonizing multiple organs and causing often infections which can lead to sepsis fatal. Studies show that nasal colonization by this organism can be cause of sepsis in hospitalized patients, where most of the patients' blood isolates are identical to those isolated from nasal cavities. The increase in number of infections caused by β-lactam antibiotics-resistant strains in hospital settings is cause of concern due to the conditions in which these patients are found, including immunosuppression conditions, in addition to the large level of virulence factors this organism carries. This study aims to identify pathological alterations, present in organs: heart, spleen, kidneys and lungs due to infection induced by methicillinresistant Staphylococcus aureus isolated from infections, as well as to nasal colonization in humans, using an experimental murine model. Six different groups of isolates were involved, ranging from methicillin-susceptible and resistant, and those carrying, or not, the Leucocidin Panton-Valentine gene. The isolates were inoculated intravenously via tail vein at a concentration of 1.0 × 107 CFU/ml and, after 72 hours, the organs were collected for histopathological analysis for inflammatory process identification. This analysis revealed significant differences in organ infections, regarding inoculated strains. Organ tissues presented the inoculated isolate, confirmed by PCR, as well as neutrophilic infiltrate predominance. However, resistance to methicillin, and presence of the Panton-Valentine leucocidin gene were not decisive factors for infection severity in mice.