Evaluación de un método colorimétrico para el estudio de la interacción entre microorganismos y células de epitelio intestinal

HUGO, A. A.; MINNAARD, J.; PÉREZ. P.F

REVISTA ARGENTINA DE MICROBIOLOGíA

Año: 2003 p. 188 - 192

0325-7541

SUMMARY The aim of the present study was to gain further insight on the reliability of the colorimetric determination of nitrite to evaluate bacterial concentrations and interaction between microorganisms and enterocyte-like cells. Seven strains of grampositive and gramnegative microorganisms were studied. Enzymatic determination of bacterial concentrations was performed on the basis of the nitrate reductase activity. Nitrite produced after incubation of the samples with a nitrate-formate solution was determined with a diazotization reaction with sulphanilic acid and N-naphthyl-ethylene-diamonium dichloride. Cell association assays were performed with differentiated Caco-2 cells. In 6 out of 7 strains studied, a biphasic relationship was found between nitrite concentration and bacterial densities. This behavior seems to be due to the sigmoideal character of the kinetics of nitrate reduction. Initial reaction rates were linearly correlated with bacterial concentrations. Association to Caco-2 cells was strongly strain dependent being Staphylococcus aureus ATCC 25923 the strain showing the highest values of association. For some strains, percentages of association calculated on the basis of the colorimetric assay were significantly higher than those calculated in terms of viable counts.