Detection of Meat Spoilage Bacteria by Using the Polymerase Chain Reaction

RAPID detection and quantification of E. coli O157/O26/O111 in minced beef by real-time PCR

AIM

To develop a real-time PCR detection procedure for Escherichia coli O111, O26 and O157 from minced meat.

METHODS AND RESULTS

Strains (n = 8) of each of E. coli O26, E. coli O111 and E. coli O157 were inoculated at ca 10-20 CFU g(-1) into minced retail meat and enriched for 6 h at 41.5 degrees C as follows: E. coli O26 in tryptone soya broth (TSB) supplemented with cefixime (50 microg l(-1)), vancomycin (40 mg l(-1)) and potassium tellurite (2.5 mg l(-1)); E. coli O111 in TSB supplemented with cefixime (50 microg l(-1)) and vancomycin (40 mg l(-1)); E. coli O157 in E. coli broth supplemented with novobiocin (20 mg l(-1)). DNA was extracted from the enriched cultures, and detected and quantified by real-time PCR using verotoxin (vt1 and vt2) and serogroup (O157 per gene; O26 fliC-fliA genes and O111 wzy gene) specific primers.

CONCLUSIONS

The methods outlined were found to be sensitive and specific for the routine detection of E. coli O111, O26 and O157 in minced beef.

SIGNIFICANCE AND IMPACT OF THE STUDY

The enrichment, isolation and detection procedures used in this study provide a rapid routine-based molecular method for the detection and differentiation of E. coli O26, O111 and O157 from minced meat.

Evaluation of four template preparation methods for polymerase chain reaction-based detection of Salmonella in ground beef and chicken

AIMS

To compare procedures for recovering template DNA from ground beef or chicken for polymerase chain reaction (PCR)-based detection of Salmonella.

METHODS AND RESULTS

The primer set of ST11 and ST15 was utilized to amplify a 429-bp product from Salmonella serotype Typhimurium. Boiling and three commercial kits were evaluated for extracting DNA from pure suspensions and artificially contaminated ground beef and chicken. The detection sensitivity of the PCR assay for pure cultures was independent of the template preparation method (P=0.946). Boiling and GeneReleaser failed to detect Salm. Typhimurium at 4 x 106 cfu g(-1) in ground chicken. PrepMan Ultra and the high pure PCR template preparation kit facilitated reliable and sensitive detection of Salm. Typhimurium in two types of food. The sensitivities were approx. 4 x 103 cfu g(-1). When spiked samples were enriched in peptone water for 6 h, an initial inoculum of 1 cfu g(-1) was detectable.

CONCLUSIONS

Four template DNA preparation methods differed in performance with respect to the type of samples tested.

SIGNIFICANCE AND IMPACT OF THE STUDY

Template DNA for the PCR detection of pathogenic bacteria, such as Salmonella in meat and poultry, could be effectively obtained using a simple rapid method such as the commercially available PrepMan Ultra kit.