Caracterización de la comunidad de enterococcus presente en queso colonia con énfasis en la distribución de resistencia a antibióticos

The cheese industry in Uruguay produces about 5.3% of the total milk production and represents 26% of the country's dairy farms, which produce 50% of the total cheese consumed in Uruguay. Colonia cheese is a typical Uruguayan cheese, produced according to the quality criteria and tradition of Swiss immigrants who settled in the Colonia dairy basin. It is a cheese of medium humidity and its main characteristic is the presence of irregular-sized eyes. In this work, Colonia cheeses from neighborhood fairs and supermarkets in Montevideo were analyzed. The microflora of these cheeses was quantified, with emphasis on the population of Enterococcus spp. The presence of enterococci in cheeses can have contradictory effects, either as a risk due to their pathogenic potential, or as a benefit to produce unique traditional products. Enterococci counts were observed in 24 of the 36 samples analyzed, with a maximum count of 1.25E+05 and an average of 1.43E+04. Resistance to different antimicrobials was also evaluated in 84 enterococci isolates. All isolates showed resistance to at least one antimicrobial. The risk of contamination of the samples with multidrug-resistant enterococci was evaluated using the MAR-Index, for which it is established that a value greater than or equal to 0.2 considers the microbial population to be at risk given the high level of observed resistance. In this study, the average MAR-Index was 0.33, so the population of Enterococcus spp. isolated from Colonia cheese represents a potential risk to human health that should be monitored.

Possible technological applications of the isolates obtained were also evaluated. Lipolytic and proteolytic activity and the production of metabolites such as diacetyl by the decomposition of citrate, all biotechnological characteristics of interest to the cheese industry, were evaluated. Of the 16 isolates selected for their low pathogenic potential, only one showed proteolytic activity and none showed lipolytic activity or utilization of citrate as the sole carbon source.