Using nested PCR to detect the hlyA gene of Listeria monocytogenes in Minas Frescal cow's milk cheese

J Food Prot. 2012 Jul;75(7):1324-7. doi: 10.4315/0362-028X.JFP-11-393.

Abstract

To evaluate a nested PCR protocol for Listeria monocytogenes detection, Minas Frescal cow's milk cheeses were produced, artificially inoculated with this pathogen at concentrations ranging from 1 to 1,000 CFU/g, and stored at 4°C for 10 days. The International Organization for Standardization (ISO) standardized method 11290-1/A1 was used to detect L. monocytogenes in the inoculated samples, and DNA was extracted from aliquots (1, 5, and 10 ml) of 1:10 dilution, followed by a nested PCR protocol for the hlyA gene. The ISO standardized reference method and nested PCR both detected L. monocytogenes at all concentrations and during all storage periods; McNemar's test showed no significant difference (P > 0.05). The results indicated that the nested PCR protocol can be used as a screening test to detect L. monocytogenes in Minas Frescal cheese, allowing earlier detection of the pathogen that can later be confirmed by the ISO standardized reference method.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Bacterial Toxins / genetics*
  • Brazil
  • Cattle
  • Cheese / microbiology*
  • Colony Count, Microbial / methods
  • Consumer Product Safety
  • DNA, Bacterial / analysis*
  • Food Contamination / analysis*
  • Heat-Shock Proteins / genetics*
  • Hemolysin Proteins / genetics*
  • Humans
  • Listeria monocytogenes / isolation & purification*
  • Polymerase Chain Reaction / methods*

Substances

  • Bacterial Toxins
  • DNA, Bacterial
  • Heat-Shock Proteins
  • Hemolysin Proteins
  • hlyA protein, Listeria monocytogenes