Empleo del sistema DIRAMIC en la determinación de la calidad microbiológica del agua

Abstract

The use of DIRAMIC system for the determination of microbiological
quality of water is suggested. The objective was to demonstrate
the possibility of using the DIRAMIC system to detect microorganisms that
indicate the quality of water faster than standard method. Another objective
was to establish a correspondence between the detection-spent time and the
concentration of microorganisms in the sample. Experimentally water
samples were inoculated with various concentrations of the main bacteria
strains indicators of water contamination and the time required for the detection
of turbidity developed in some culture media used in the standard
methods, were determined. From the analysis of results, culture media with
the higher growth indexes in the shortest times were selected and the range
of time required for the detection of various microbial concentrations were
established. For the specific detection of Escherichia coli 4-methylumbelliferyl-
b-D-glucuronide and tryptophan were added to EC broth. Finally,
a sterile drinkable water sample was inoculated with a mix of the bacterial
strains under study, adjusting its concentration to real samples; the results were
the same as with the single strains of microorganisms. All cellular concentrations
were verified through the multiple tube fermentation and membrane filter
methods. DIRAMIC system for the determination of microbiological quality of
water would allow shortening the time to detect the microorganisms that indicate
such quality, and to decrease disposable material costs.