Abstract

ALFONSO VALDES, Ivonne et al. Evaluation of beef heart papainic peptone for selective enrichment of Enterococcus. Rev Cubana Invest Bioméd [online]. 2013, vol.32, n.4, pp. 445-0. ISSN 0864-0300.

Introduction: microbiological control of water and food has motivated the development of selective culture media capable of detecting Enterococcus, which need an appropriate source of energy to ensure the recovery of microorganisms. Objectives: compare different nutrient bases produced from food products and by-products according to their growth promotion capacity for the genus Enterococcus, and evaluate the accuracy of dextrose azide broth culture medium. Methods: eighty strains of different genera were selected for the test. Two experimental variants of dextrose azide broth were prepared (one buffered) and the microorganisms selected were inoculated at a standardized concentration. Biomass increase was determined by measuring optical density in a spectrophotometer at 640 nm every 1 h. Microbiological evaluation of the culture medium was carried out using different microbial genera at different concentrations. Diagnostic and relative sensitivity, specificity and accuracy, and the Kappa index were determined for the culture medium. Glucose azide broth (Merck, Germany) was used as reference medium. Results: the Enterococcus species evaluated showed higher biomass production than the other genera. The buffered formulation showed maximum growth of culture and this medium exhibited a higher inhibitory effect on the strains selected as negative control bacteria. The culture medium showed satisfactory results for diagnostic sensitivity, specificity and accuracy (97.7; 94.6; 96.3 %, respectively) and relative sensitivity, specificity and accuracy (100; 89.8; 94.8 %, respectively). These values were higher than those obtained with the reference medium. Kappa indices were ranged as "almost perfect". Conclusions: with the nutrient base obtained from beef heart, a by-product from the food industry (beef heart papainic peptone), better growth of the genus Enterococcus is obtained, as well as higher accuracy in the formulation when it is used as the main source of nutrients.

Keywords : dextrose azide broth; Enterococcus; isolates; nutrient bases.

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