Use of polymerase chain reaction for detection of Listeria monocytogenes in food

Abstract

was used to analyze food for the presence of Listeria monocytogenes. Food samples were artificially contaminated to develop two procedures to detect the organism following enrichment steps. Procedure A was based on dilution of the enrichment broth followed by lysis of the bacteria and direct analysis of the lysate with PCR. With procedure A and artificially contaminated food samples, it was possible to detect fewer than 10 bacteria per 10 g of food. In procedure B, centrifugation was used to concentrate bacteria before lysis and PCR. With procedure A, 330 naturally contaminated food samples of several types were analyzed. Twenty samples were found to be positive for L. monocytogenes, which was in agreement with the classical culture technique. By using procedure B on a subset of 100 food samples, 14 were found to be positive by PCR whereas the classical culture method detected only 13. Analysis times, including enrichment steps, were 56 and 32 h with procedures A and B, respectively.

Detection of Erwinia carotovora subsp. atroseptica and Erwinia chrysanthemi in potato tubers using polymerase chain reaction

“…Thus a detection method based on PCR combines a high degree of specificity with a high degree of sensitivity. PCR technology has been successfully developed as a tool for specific and sensitive detection of micro-organisms in clinical samples (Hartskeer et al, 1989), environmental samples (Bej et al, 1991;Atlas et al, 1992), food or dairy samples (Harris & Griffiths, 1992;Niederhauser et al, 1992;Starbuck et al, 1992) and plant samples (Blakemore et at., 1992;Dong et al, 1992), In particular, food, milk and plant samples often contain components that significantly inhibit the polymerase chain reaction (Demeke & Adams, 1992;Rossen et al, 1992;Powell 6/a/., 1994).…”

Correlation between the Presence of Virulence‐Associated Genes as Determined by PCR and Actual Virulence to Mice in Various Strains of Listeria Spp.

“…The virulence-associated genes mentioned above can be used as the target DNA for polymerase chain reaction (PCR). It is reported that prfA and hlyA are detected by PCR distinctively in L. monocytogenes suggesting the usefulness of PCR amplification of these genes for the identification of L. monocytogenes from various food samples (19,30 Listeria for humans, it is not known whether various L. monocytogenes strains exhibit a similar level of virulence. To determine the validity of PCR-based amplification of virulence-associated genes in the detection of virulent strains, we examined the actual virulence to mice in parallel with PCR amplification of each gene using various strains of L. monocytogenes and L. innocua.…”

Estimation of Spoilage Bacterial Load on Meat by Fluorescein Diacetate Hydrolysis or Resazurin Reduction

“…A 25-cm 2 area of each steak surface was swabbed with two sterile cotton swabs which were subsequently washed and expressed into a tube containing 10 mL sterile peptone water (0.1%). The tube was centrifuged at 100 ϫ g for 30 sec to sediment meat particles according to Neiderhauser et al (1992). The supernatant was transferred into a new tube and centrifuged at 3000 ϫ g for 30 min to pellet the bacterial cells.…”