Abstract The plasmid-encoded toxin (Pet) is one of the most studied Enterobacteriaceae autotransporters produced by the enteroaggregative Escherichia coli (EAEC). It is responsible of morphological changes in enterocytes during EAEC infection. Recently, Pet was found in the genome of the Proteus mirabilis RTX339 strain [P. mirabilis (Pet+)]. P. mirabilis causes complicated urinary tract infections (UTI) in patients having urinary catheters and structural or functional abnormalities. In this study, an UTI was induced in BALB/c female mice with the P. mirabilis (Pet+) strain. Mice infected by P. mirabilis (Pet+) showed bacterial colonization in bladder and kidney, from the second up to the tenth day post-infection. Morphological changes were evidenced by histology. Multiple exfoliated rounded cells were observed in the bladder transitional epithelium, as well as, structural cell alterations in the kidney cortex. The presence of Pet into exfoliated and parenchymal cells was confirmed by confocal microscopy. Cytoskeleton alterations were observed in those sites where Pet was detected. Pet expressed by P. mirabilis (Pet+) strain, contributes to its pathogenicity, affecting urinary tissues during the course of the infection.

Resumen La toxina Pet (plasmid-encoded toxin) producida por Escherichia coli (EAEC) es uno de los autotransportadores más estudiados en la familia Enterobacteriaceae. Es responsable de cambios morfológicos en enterocitos durante la infección por EAEC. Recientemente, Pet fue encontrada en el genoma de una cepa de Proteus mirabilis RTX339 [P. mirabilis (Pet+)]. P. mirabilis causa infección en el tracto urinario (ITU) en pacientes que usan catéteres o que presentan anomalías estructurales o funcionales. En este estudio una ITU con P. mirabilis (Pet+) fue inducida en ratones hembras BALB/c. Los ratones infectados con P. mirabilis (Pet+) muestran una colonización bacteriana en vejiga y riñón desde el segundo hasta el día decimo de la infección. Los cambios morfológicos fueron evidenciados por histología. Se observaron múltiples células exfoliadas del epitelio de transición de la vejiga, así como alteraciones morfológicas en la corteza renal. Se confirmó la presencia de Pet en las células exfoliadas y en las del parénquima por microscopía confocal. Las alteraciones del citoesqueleto fueron observadas en los sitios donde se detectó Pet. La toxina Pet expresada por la cepa de P. mirabilis (Pet+) contribuye a la patogenicidad y afecta tejidos urinarios durante el curso de la infección.

BACKGROUND Dialyzable leukocyte extracts (DLEs) contain molecules smaller than 10 kDa with biological activity in receptor organisms. Primarily, they participate in the regulation of the Th1 immune response, which is essential for the control of several intracellular infections, such as toxoplasmosis. This disease is associated with congenital infection, encephalitis or systemic infections in immunocompromised individuals. The clinical course of this infection fundamentally depends on a well-regulated immune response and timely treatment with the appropriate drugs. OBJECTIVE The aim of this study was to evaluate the effect of treatment with a leukocyte extract, derived from crocodile lymphoid tissue, on the histopathology and brain parasite load in NIH mice that had been infected with cysts of Toxoplasma gondii (ME-49 strain). METHODS The treatment was applied during the acute and chronic stages of the infection. Histopathological changes were evaluated in the ileum, liver and spleen at one, four and eight weeks after infection and in the brain at week 8. The parasite load was evaluated by counting the cysts of T. gondii found in the brain. FINDINGS Compared to the control mouse group, the mice infected with T. gondii and under treatment with DLE showed less tissue damage, mainly at the intestinal, splenic and hepatic levels. In addition, a greater percentage of survival was observed, and there was a considerable reduction in the parasite load in the brain. CONCLUSIONS The results suggest that DLE derived from crocodile is a potential adjunctive therapy in the conventional treatment of toxoplasmosis.