Efecto de distintos antimicrobianos sobre el crecimiento de Listeria monocytogenes

Abstract

The effectiveness of two organic acids included in the positive list for additives, sodium lactate (E-325) and sodium diacetate (E-262), was evaluated against Listeria monocytogenes growth. Different concentrations of these additives were added to the liquid culture medium. The optical density increments at 600 nm was measured for a 24 hours period under 37 0C, using non-inoculated medium as blank. The measurements were taken every hour in sterile 96 wells plates each. After this analysis, a graphical representation of absorbance increment against time was done, extrapolating the maximum absorbance increment rate (μ) and the minimum time required to detect an absorbance increment (λ) from the graphic. These two parameters made possible to evaluate the bacterial growth. After the analysis of λ and μ for lactate concentrations, a negative effect in bacterial growth was observed, extending λ value. Nevertheless, once the bacterial growth started, any effect on μ value was detected. A higher inhibitory effect was observed after the analysis of these parameters for diacetate concentrations, an extension on λ value as well as a μ value descent was found. In this way, a total inhibition of growth occurred when diacetate concentration was 0,2% or higher.