Resumen

APAZA PACO, JUAN PABLO; ASPILLAGA SANCHEZ, HILDA LUZ  y  ESPADA SILVA, ANGÉLICA MARIA. Evaluation of the performance indicators of 3M Petrifilm Staph Express (STX) against the ISO 6888-1: 2003 standard in the count of Staphylococcus aureus in fresh cheeses by artificial contamination. Rev.Cs.Farm. y Bioq [online]. 2018, vol.6, n.1, pp.15-26. ISSN 2310-0265.

Abstract Staphylococcus aureus can contamínate a wide range of foods, being fresh cheeses a differential and selective medium for the development of this microorganism, reach-ing the production of thermostable entero-toxin causing a staphylococcal intoxication transmitted by food. The use of the 3M Petrifilm Staph Express (STX) method has considerable ad-vantages over the conventional or reference method, facilitating and favoring many tech-nical and economic aspects, within them we have the optimization of time as regards the preparation of culture media, need for equipment, infrastructure requirements, lower personnel requirements and decreas-es the costs of the use of electricity con-sumption, decreases the generation of solid waste, among others. The comparison between the alterna-tive method and the conventional method was made by means of the artificial contam-ination of a free matrix of S. aureus and a low accompanying microbiota count, where different levéis of contamination were es-tablished, evaluating the performance indi-cators (relative accuracy, relative precisión, linearity, calibration curve and limit of quan-tification). In the relative accuracy indicator, 95.6% recovery was obtained for the lowest level (approximately 8 CFU / g) and 98.7% recovery for the highest level of contamination (approximately 5300 CFU / g), with a range of 70 to 120% acceptance. For the relative precision, the RSD of all the tested levels was calculated, obtaining data that accept the relative accuracy of the dry rehydratable plate method because the values were low-er than the calculated theoretical RSD. The limit of detection was tested with <10 CFU / g, obtaining a CV of 1.16%. Based on the results obtained, we can conclude that the 3M Petrifilm Staph Express (STX) method complies with the performance indicators againstthe ISO 6888-1: 2003 standard

Palabras clave : S. aureus; fresh cheese; rehydratable dry plate; artificial contamination.

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