Microbiological Quality of Spanish Aged Cheeses and the Antimicrobial Resistance Profiles of Associated Enterococci, Staphylococci and Enterobacterales

The aim of this work was to evaluate the microbiological quality of Spanish aged cheeses and the antimicrobial resistance of enterococci, staphylococci and Enterobacterales. A total of 60 aged cheeses produced in northern Spain were collected at the retail level. Mesophiles, lactic acid bacteria, staphylococci, enterococci, Enterobacterales, and yeast counts were determined. More microbial diversity was found in raw milk cheeses than in those elaborated with pasteurized milk. In general, lactic acid bacteria were the dominant microorganism, mainly Lactiplantibacillus lactis. High resistance rates were observed in E. faecalis strains isolated from raw milk cheeses (74.42%), being 9.30% multi-resistant. The dominant staphylococci found was Staphylococcus equorum. Multi-resistant S. equorum strains were isolated both from raw (1.69%) and pasteurized milk cheeses (9.09%). Hafnia alvei was the predominant bacterium in raw milk cheeses. Fifteen Enterobacterales strains, isolated from raw milk cheeses, showed multi-resistance (37.5%), and seven strains were ESBL producers (17.5%). Escherichia coli was only isolated from 5. 56% of raw milk cheeses, but all of them were extended-espectrum B-lactamase (ESBL) producers. The dominant yeast was D. hansenni, followed by Kluyveromyces lactis.