Efeito do aspartato sobre o crescimento e formação de biofilmes por Staphylococcus aureus

Abstract

Staphylococcus aureus is an opportunistic pathogen of great relevance, since it is often associated with outbreaks of food poisoning. When submitter to some type of cell stress, certain microorganisms tend to cluster in the form of a biofilm, becoming more resistant to external agents, including antimicrobial treatments such as the use of the bacteriocin nisin. Aspartate is an important molecule for cellular metabolism, as there is evidence of its role in maintaining cellular homeostasis and also in the expression of virulence factors. This study aimed to evaluate the possible influences of the amino acid aspartate on growth, adhesion, and biofilm formation by S. aureus. The influence of the bacteriocin nisin, in subinhibitory concentrations, on the formation of biofilm on a polystyrene surface in the presence and absence of aspartate was also evaluated. Cell growth was conducted in a synthetic medium supplemented or not with the amino acid in two conditions, aerophilic and microaerophilic, in conical flasks under orbital assembly and into 96-well microplates, respectively. Cell adhesion and biofilm formation were studied on two surfaces commonly used in the food industries, stainless steel and polystyrene, and the biofilm formation on this last surface was also evaluated in the presence of subinhibitory dosages of nisin. S. aureus grew reaching maximum absorbance, both in aerobic and microaerobic conditions in synthetic medium with aspartate. Cell adhesion on a polystyrene surface did not show a significant difference (p> 0.05) in the presence or absence of aspartate. On the other hand, in stainless steel surface, the initial adhesion was higher in medium supplemented with aspartate (p <0.05), but there was no difference in the biofilm formed after 24 and 48 h in the presence or absence of the amino acid. Subinhibitory concentrations of nisin did not influence cell adhesion on a polystyrene surface. The results highlight the effect of aspartate on the microbial growth and initial adhesion of the microorganism on stainless steel. Further studies, evaluating different strains of S. aureus, need to be carried out to obtain more conclusive responses to the role of the amino acid for this species.