Growth conditions affect biofilms of Staphylococcus aureus producing mastitis: Contribution of MALDI-TOF-MS to strain characterization.

Bovine mastitis is a disease of dairy cattle prevalent throughout the world that causes alterations in the quality and composition of milk, compromising technological performance. Staphylococcus aureus is one of the most important pathogens that produce clinical, subclinical, and chronic mastitis. Biofilms are considered a virulence factor necessary for the survival of S. aureus in the mammary gland. Its zoonotic potential is important not only for the dairy industry sector but also for public health. This study aimed to evaluate the effect of different growing culture conditions on the biofilm formation of S. aureus isolated from mastitis and to test the MALDI-TOF-MS's ability to discriminate among different biofilm formation levels. Fluids commonly found in the dairy environment were incorporated to approach the pathogen's behavior in natural surroundings. PIA production was also evaluated. All strains were able to form high biofilms in TSB, TSBg, and milk. Milk changed the behavior of some strains which formed more biofilms in this medium than in TSBg. The free iron medium CTSBg and milk whey inhibited the biofilm formation of the most strains. MALDI-TOF-MS performance was an excellent tool to discriminate between high, moderate, and low biofilm producers strains of S. aureus in each media, confirming the results of crystal violet assay. PIA production was variable among the strains and showed a media-dependent behavior. Our data highlights the importance of considering the growing conditions that mimic the natural ones to the study of biofilm formation in vitro.

Salmonella enterica serovar Enteritidis enterocolitis during late stages of gestation induces an adverse pregnancy outcome in the murine model.

Foodborne diseases caused by Salmonella enterica serovar Enteritidis (S. Enteritidis) are a significant health problem. Pregnancy, state of immunological tolerance, is a predisposing condition for the development of infections with intracellular pathogens. Salmonella species can cause pregnancy complications such as chorioamnionitis, transplacental fetal infection, pre term labor, abortions, neonatal and maternal septicemia. However, the specific mechanisms by which Salmonella infections trigger these alterations are not clear. In the present work, using a self-limiting enterocolitis murine model, we show that the ingestion of a low dose of S. Enteritidis at late stages of pregnancy (day 15 of gestation) is sufficient to induce massive maternal infection. We found that Salmonella infection leads to 40% of pre term delivery, 33% of abortion and fetal growth restriction. Placental dysfunction during S. Enteritidis enterocolitis was confirmed through cellular infiltration and hypoxia markers (MPO activity and COX-1 and COX-2 expression, respectively). Apoptosis in placental tissue due to Salmonella infection was also evident at day 18 of gestation when investigated by morphometric procedure, DNA fragmentation and Fas/FasL expression. Also, the expression of IFN-γ, TNF-α, IL-17 and IL-10 was up regulated in response to Salmonella not only in placenta, but also in amniotic fluid and maternal serum. Altogether, our results demonstrate that S. Enteritidis enterocolitis during late stages of gestation causes detrimental effect on pregnancy outcome.