Introduction: L. monocytogenes represents a concern in the production of Gorgonzola PDO cheese. The ubiquitous nature of the pathogen and its adaptability pose a risk for this production. Rational: The aim of this study was to investigate the presence of genus Listeria in the Gorgonzola production chain, in order to identify dissemination pathways. For this reason one producer and all the conferring farms (N=20) were selected. A total of 200 samples were collected in four visits (May 2008 - October 2009), divided into: milk from each farm (N=20), milk from receiving tanks (N=3), and sponges from equipment, environments and surfaces (N=27). Samples were processed using ISO 11290-1 method. Suspected L. monocytogenes colonies were identified through specific PCR, whereas the others were challenged with 16S DNA PCR and then sequenced. Results: Listeria innocua was identified in 3 samples of farm milk. Listeria spp. and L. monocytogenes were retrieved from 20 sponges out of 108 (19%). L. monocytogenes alone was identified in 7 samples, L. innocua in 12 and both were identified in one sample. Contaminated sponges were retrieved from stewing, ripening, perforating and salting equipments, carts, sink and cutting blade. In 5 surfaces/equipments contamination was recurrent. Conclusion: Noteworthy, low levels of contamination were detected in milk samples prior to pasteurisation. Contrarily, surfaces and equipment in contact with ripening cheese were frequently contaminated. The finding of contaminated salting and perforing equipments, as well as moving carts may contribute to dissemination. The detection of Listeria in the same site on different visits should be looked at carefully, as it may indicate the presence of persistent strains adapted to specific niches. Nonetheless, considering that rinds are not edible according to EU legislation, the presence of the pathogen on cheese rinds cannot be considered a risk for the consumer. Acknowledgements: Founds granted by Regione Piemonte - Direzione sviluppo Agricoltura - 2007.
Presence of Listeria along the Gorgonzola P.D.O. production chain
NUCERA, Daniele Michele;CIVERA, Tiziana;MORRA, Patrizia;GRASSI, Maria Ausilia
2010-01-01
Abstract
Introduction: L. monocytogenes represents a concern in the production of Gorgonzola PDO cheese. The ubiquitous nature of the pathogen and its adaptability pose a risk for this production. Rational: The aim of this study was to investigate the presence of genus Listeria in the Gorgonzola production chain, in order to identify dissemination pathways. For this reason one producer and all the conferring farms (N=20) were selected. A total of 200 samples were collected in four visits (May 2008 - October 2009), divided into: milk from each farm (N=20), milk from receiving tanks (N=3), and sponges from equipment, environments and surfaces (N=27). Samples were processed using ISO 11290-1 method. Suspected L. monocytogenes colonies were identified through specific PCR, whereas the others were challenged with 16S DNA PCR and then sequenced. Results: Listeria innocua was identified in 3 samples of farm milk. Listeria spp. and L. monocytogenes were retrieved from 20 sponges out of 108 (19%). L. monocytogenes alone was identified in 7 samples, L. innocua in 12 and both were identified in one sample. Contaminated sponges were retrieved from stewing, ripening, perforating and salting equipments, carts, sink and cutting blade. In 5 surfaces/equipments contamination was recurrent. Conclusion: Noteworthy, low levels of contamination were detected in milk samples prior to pasteurisation. Contrarily, surfaces and equipment in contact with ripening cheese were frequently contaminated. The finding of contaminated salting and perforing equipments, as well as moving carts may contribute to dissemination. The detection of Listeria in the same site on different visits should be looked at carefully, as it may indicate the presence of persistent strains adapted to specific niches. Nonetheless, considering that rinds are not edible according to EU legislation, the presence of the pathogen on cheese rinds cannot be considered a risk for the consumer. Acknowledgements: Founds granted by Regione Piemonte - Direzione sviluppo Agricoltura - 2007.File | Dimensione | Formato | |
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