Detection of Salmonella spp. in food by a rapid PCR-hybridization procedure.
A rapid and sensitive PCR-hybridization procedure for detection of Salmonella serovars in food samples was developed. This method is based on three subsequent steps: (1) extraction of nucleic acids from a 2 ml aliquot of the pre-enrichment medium used for the conventional culture method after 6 h of incubation at 37 degrees C; (2) amplification with primers selected from the sequences of invE and invA genes; (3) Southern blot and hybridization with a biotin labeled oligonucleotide probe. The entire procedure requires 30 h. The PCR-hybridization assay was able to detect as little as 50 fg of purified chromosomal DNA of S. typhimurium and 0.2 cfu g-1 of an artificially contaminated food sample. Of 245 food samples analyzed by culture and PCR-hybridization, 20 were positive by both methods and 16 were positive by PCR-hybridization only. None of the 209 PCR-negative samples tested positive by culture. The sensitivity, specificity, alpha and beta error values of the results of the PCR-hybridization procedure, compared with those of culture, were 100, 92.9, 0 and 7.1%, respectively. These results indicate that a short pre-enrichment and PCR-hybridization could be used as a screening test for the detection of Salmonella in food samples.
Nastasi
A
A
Department of Hygiene and Microbiology G. D'Alessandro, Università degli Studi, Palermo, Italy.
Mammina
C
C
Mioni
R
R
D000821:Animal Feed / Q000382:microbiology*; D001431:Bacteriological Techniques; D004269:DNA, Bacterial / Q000302:isolation & purification; D005516:Food Microbiology; D008460:Meat / Q000382:microbiology*; D009693:Nucleic Acid Hybridization / Q000379:methods*; D016133:Polymerase Chain Reaction / Q000379:methods*; D012475:Salmonella / Q000302:isolation & purification*; D012680:Sensitivity and Specificity
D004269:DNA, Bacterial