Pathological profiles of systemic infections by Panton-Valentine leukocidin-positive, methicillin-resistant Staphylococcus aureus strains in a murine model.

AIMS: Staphylococcus aureus is one of the most common pathogens in hospital environment and community. Panton-Valentine leukocidin (PVL) production is clinically associated with skin abscesses, soft tissues infections, bacteraemia and sepsis. This study aimed to investigate the effects of the presence of genes lukF/S-PV coding for PVL, in histological and haematological features during systemic infection, using a Swiss mice experimental model. METHODS AND RESULTS: Experiments were performed using 25 mice distributed into five experimental groups, intravenously inoculated with 50 µl suspensions at density 1·0 × 107  CFU per ml of strains: methicillin-susceptible (MSSA) and pvl-negative strains isolated from nasal colonization; MSSA pvl-positive strains isolated from nasal colonization; methicillin-resistant (MRSA) and pvl-positive strains isolated from peripheral blood of a patient with severe pulmonary infection; and a MRSA pvl-positive strains isolated from a peripheral blood culture of a patient with bacteraemia. Haematological analysis was performed at 24, 48, 72 and 96 h post-infection. Morphoanatomy and histopathological analyses were performed at 96 h post-infection. For all S. aureus strains tested, the capability of intravenous dissemination and survival into mice tissues was demonstrated. Inflammatory processes at different levels were related to the presence of pvl genes, and included alterations in the format, size and colour of the organs. Staphylococcus aureus pvl-positive strains were detected in greater numbers in the organs of the infected animals. CONCLUSIONS: The pvl-positive strains isolated from blood cultures were capable to induce the greatest modifications in both haematological and histopathological profiles, and seemed to aggravate the systemic infections. SIGNIFICANCE AND IMPACT OF THE STUDY: These findings are valuable in characterizing infections caused by S. aureus in humans and murine.

Influence of omega-3 fatty acids from the flaxseed (Linum usitatissimum) on the brain development of newborn rats.

OBJECTIVES: The importance of essential fatty acids, in particular the omega-3 family, in the central nervous system development of newborns is well documented. The flaxseed (Linum usitatissimum) is considered one of the best vegetable sources of omega-3 fatty acids. The influence of omega-3 fatty acids from flaxseed on the brain development of newborn rats was evaluated. MATERIAL AND METHODS: Pups of the F1 generation were obtained from 18 female Wistar rats divided in 3 groups (n=6), FG: fed with diet based on Flaxseed added with casein, CG: Casein, and MCG: Modified Casein supplemented with fibers and soybean oil. Newborn pups were weighted and submitted to euthanasia; brains were collected for evaluation of weight and lipid profile through gaseous chromatography. RESULTS: Significant increase in brain weight (39%) and relative brain weight (37%) was verified in pups from mothers fed with flaxseed diet. The omega-3 (n-3) fatty acids from the flaxseed were found in abundance in the diet made with this oleaginous and also significant increase in docosahexaenoic acid (DHA) (38%), as well as in total of omega-3 (n-3) fatty acids (62%). CONCLUSION: Maternal diet of flaxseed during pregnancy influences the incorporation of omega-3 fatty acid in the composition of brain tissue, assuring a good development of this organ in newborn rats.