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Ricchi M.,National Reference Center for Paratuberculosis | De Cicco C.,National Reference Center for Paratuberculosis | Kralik P.,Veterinary Research Institute | Babak V.,Veterinary Research Institute | And 6 more authors.
FEMS Microbiology Letters | Year: 2014

The causative agent of paratuberculosis in ruminants, Mycobacterium avium subsp. paratuberculosis (MAP), although still a matter of debate, has been linked with Crohn's and other human diseases. The availability of rapid methods for assessing the viability of MAP cells in food, in particular milk, could be of great use for risk management in food safety. MAP viability is generally assessed using culture techniques that require prolonged incubation periods for the growth of MAP. To differentiate between viable and nonviable MAP cells in milk samples, this study explores the combination of two already described techniques: peptide magnetic bead separation followed by Propidium Monoazide qPCR. Using an Ordinal Multinomial Logistic Regression model to analyze the results obtained after spiking milk samples with mixtures containing different percentages of viable/dead cells, we were able to assess the probability of the viability status of MAP found in milk. This model was applied to contaminated pasteurized milk to ascertain the efficacy of heat treatment in MAP killing. The method reported herein can potentially be used for direct detection of MAP viability in milk. © 2014 Federation of European Microbiological Societies. Published by John Wiley & Sons Ltd. All rights reserved.


Savi R.,National Reference Center for Paratuberculosis | Ricchi M.,National Reference Center for Paratuberculosis | Cammi G.,National Reference Center for Paratuberculosis | Garbarino C.,National Reference Center for Paratuberculosis | And 3 more authors.
Veterinary Microbiology | Year: 2015

Paratuberculosis of ruminants is characterised by chronic enteritis but, at advanced stages of the disease, a systemic dissemination of Mycobacterium avium subsp. paratuberculosis (MAP) in tissues and organs can occur. MAP has been recovered from lymph nodes and muscles of clinical and sub-clinical cows. In most countries, dairy and beef cattle infected with paratuberculosis are routinely sent to slaughter and the consumption of their meat could be a possible route of human exposure to MAP. However, few studies on MAP in ground beef are currently available. During the period November 2013-March 2014 we carried out a survey on the ground beef produced in an industrial meat processing plant. One-hundred and forty samples of ground meat were analysed by IS900-qPCR and culture (VersaTrek System®). The limit of detection (LOD) of qPCR was 630 MAP cells/g (107 CFU/g) while the LOD for culture was 170-230 MAP cells/g (62-115 CFU/g). No samples were positive by direct IS900 qPCR, while two samples were positive by liquid culture. Our data suggest that the presence of live MAP in raw minced meat is possible. In order to avoid exposure for humans through the consumption of contaminated meat, proper cooking of meat is recommended. © 2015 Elsevier B.V.


Ricchi M.,National Reference Center for Paratuberculosis | Barbieri G.,National Reference Center for Paratuberculosis | Cammi G.,National Reference Center for Paratuberculosis | Garbarino C.A.,National Reference Center for Paratuberculosis | Arrigoni N.,National Reference Center for Paratuberculosis
FEMS Microbiology Letters | Year: 2011

Analysis of micro- and minisatellite loci is widely used in sub-typing of Mycobacterium avium subsp. paratuberculosis. Microsatellite (short sequence repeat, SSR) loci have shown highest discriminatory power, but direct sequencing of amplicons is required for correct assignment of the repeat number. We developed an alternative method to sequencing, focusing on the SSR8 locus (constituted by GGT triplets from three to six repeats). The approach is based on asymmetric quantitative PCR, followed by high-resolution melting analysis with unlabelled probes (UP-HRM). Data showed perfect concordance between direct sequencing and UP-HRM, which is faster, simpler and more cost effective. © 2011 Federation of European Microbiological Societies. Published by Blackwell Publishing Ltd. All rights reserved.

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