Resumen

PETROLA, Maribel; PINTO, Andrealicia; LUIGI-SANDOVAL, Teresita  y  ROJAS, Tomás. Comparison of Magnetic Immunoseparation technique and the conventional method for isolation of Salmonella spp. from artificially contaminated pasteurized milk. Salus [online]. 2011, vol.15, n.3, pp.19-23. ISSN 1316-7138.

Pasteurized milk is an excellent substrate for Salmonella and therefore requires a thorough quality control to ensure its safety for human consumption. The aim of this study was to compare the techniques of Magnetic Immunoseparation (MIS) and the conventional method (CM) for the detection of Salmonella spp. in artificially contaminated pasteurized milk. Six groups of pasteurized milk samples were artificially contaminated with 50 cells/mL of Salmonella spp. plus 1 x 10³ cells/mL of a "cocktail" of Enterobacteriaceae (Escherichia coli, Klebsiella oxytoca, Shigella boydii and Enterobacter cloacae). Salmonella growth by MC (COVENIN 1291-2004) and MIS was evaluated using different protocols of the latter, varying the dilution factor (without dilution and 10³) and the number of washes (3 and 5). Results: We succeeded in recovering Salmonella spp. by MIS from selective enrichment broth and pre-enrichment of CM. The MIS reduced the time for obtaining results down to three days with respect to CM. Bacterial recovery was not achieved by applying MIS directly into inoculated pasteurized milk. It was shown that the sample dilution factor did not influence MIS results, while the number of washings during the procedure greatly influenced them. The CM was able to recover Salmonella spp. in 100% (n=30) of the samples. Conclusion: The application of the MIS for the isolation of Salmonella spp. in samples of pasteurized milk significantly reduces the time for obtaining results with respect to CM.

Palabras clave : Milk; Salmonella spp; magnetic immunoseparation.

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