Rapid detection of Salmonella in milk by combined immunomagnetic separation-polymerase chain reaction assay


Taban B. M. , Ben U., Aytac S. A.

JOURNAL OF DAIRY SCIENCE, vol.92, no.6, pp.2382-2388, 2009 (Journal Indexed in SCI) identifier identifier identifier

  • Publication Type: Article / Article
  • Volume: 92 Issue: 6
  • Publication Date: 2009
  • Doi Number: 10.3168/jds.2008-1537
  • Title of Journal : JOURNAL OF DAIRY SCIENCE
  • Page Numbers: pp.2382-2388

Abstract

During the past few years, milk has presented a risk of Salmonella contamination; it has been implicated as the cause in several outbreaks of salmonellosis. Because conventional detection methods require 5 to 7 d for completion and involve several subcultivation stages followed by biochemical and serological tests, rapid and sensitive methods have been sought, mainly at the DNA level. Therefore, a study including milk samples was conducted to evaluate the performance of a combination of 2 techniques-immunomagnetic separation and polymerase chain reaction (PCR)-for the detection of Salmonella. The 16-, 14-, 12-, 10-, and 8-h nonselective pre-enrichment steps before immunomagnetic separation and the high-pure DNA preparation method before PCR were used in a combined assay. Milk samples, which were found to be Salmonella-negative by a reference method, were first inoculated with Salmonella Enteritidis. Next, the shortest preenrichment time that is required for detection of 1 or 10 cfu of Salmonella/mL by combined immunomagnetic separation-PCR assay was found by using 16-, 14-, 12-, 10-, and 8-h incubation periods. The detection limit using a 16-, 14-, or 12- h nonselective pre-enrichment was 1 to 10 cfu/mL. However, the sensitivity decreased to 10(1) and 10(2) cfu/mL, respectively, when 10- and 8-h pre-enrichments were used. This assay, in conjunction with a 12-h pre-enrichment, proved to be rapid (overall 16 h) and sensitive (1-10 cfu/mL) for the detection of Salmonella in milk samples and promising for routine use in the detection of Salmonella in milk.