Comparison of "Gen-Probe" DNA probe and PCR for detection of Listeria monocytogenes in naturally contaminated soft cheese and semi-soft cheese.
A comparison was made of three approaches for the detection of Listeria monocytogenes in naturally contaminated soft cheese and semi-soft cheese after enrichment. Enrichment broths were tested by plating them onto different selective agars, by "Gen Probe" DNA hybridization and by the polymerase chain reaction (PCR). Based on two-step enrichment, all three approaches showed high specificities (90% or more) in detecting L. monocytogenes. In contrast, the sensitivity of the Gen-Probe test was low (33% or less), whereas high sensitivities were obtained with selective plating and PCR (83% or more). Based on one-step enrichment, specificities again were high for selective plating and PCR assay (100%), whereas for the Gen-Probe assay the specificity was lower (88% or more). The best sensitivities were observed with selective plating (67%) and PCR (75%). In terms of sensitivity, specificity and analysis time, PCR applied to a two-step enrichment was the most powerful assay for detecting L. monocytogenes in soft and semi-soft cheese.
Niederhauser
C
C
Laboratory of Food Chemistry, University of Berne, Switzerland.
Höfelein
C
C
Lüthy
J
J
Kaufmann
U
U
Bühler
H P
HP
Candrian
U
U
D002611:Cheese; D003470:Culture Media; D015342:DNA Probes / Q000235:genetics*; D005516:Food Microbiology; D017403:In Situ Hybridization; D066298:In Vitro Techniques; D008089:Listeria monocytogenes / Q000235:genetics / Q000302:isolation & purification*; D016133:Polymerase Chain Reaction / Q000379:methods*
D003470:Culture Media; D015342:DNA Probes