US 8,298,786 B2Granted

Colorimetric method and relative device for bacterial load detection

AssigneeMBS S.r.l

InventorsGiovanni Antonini, Alberto Mari, Maria Teresa Massucci

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Abstract

A method for detecting a bacterial load comprising adding a sample for analysis to an analysis reagent in a sterilized reaction container, thermostatting the reaction container at a temperature of between 25 and 45° C., and verifying the change in colouring of the analysis reagent. The analysis reagent is an aqueous solution comprising amino acids chosen from the group consisting of meat peptones, vegetable peptones, casein hydrolysates, tryptose, tryptones and yeast extract; glucides chosen from monometric or oligomeric glucides metabolisable by micro-organisms; a buffer system suitable for maintaining the pH between 5.5 and 8.5; a redox indicator with potential between −250 and +250 mV and/or a pH indicator with colour change interval between pH 4.0 and pH 9.0; and a water-immiscible organic liquid compound having a lower density than water and suitable for separating the aqueous phase from a gaseous phase existing prior to the analysis or formed during the reaction.

Claims15

Dependent claims

A method for the detection of bacterial load, the method comprising:

adding a sample to be analysed to an analysis reagent in a suitable reaction container that is appropriately sterilised, wherein the reaction container is at a temperature between about 25 and about 45° C.;
verifying a colour change of the analysis reagent;
and once the verifying has been completed, adding a sterilising substance in the reaction container without opening the reaction container;
wherein the analysis reagent is an aqueous solution comprising:
from about 1 to about 100 g/l of at least one source of amino acids chosen from the group consisting of meat peptones, vegetable peptones, casein hydrolysates, tryptose, tryptones, and yeast extract;
from about 0 to about 200 g/l of a buffer system suitable for maintaining the overall pH between about 5.5 and about 8.5;
from about 0.03 to about 3 g/l of a redox indicator with a potential between about −250 and about +250 mV;
a pH indicator with a colour change interval between a pH of about 5.5 and a pH of about 8.5;
from about 0 to about 200 g/l of a selective agent for the detection of a specific class of bacteria;
and
an organic liquid compound that is not miscible with water and having a lower density than water and suitable for separating an aqueous phase from a gaseous phase existing prior to the verifying or formed during a reaction between the sample and the analysis reagent;
calculating a time for the colour change to occur;
and
determining a concentration of the bacteria load present in the sample at least partially based on the time.

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Dependencies are inferred from the claim text.