Showing papers by "Frederique Pasquali published in 2014"

Behavior of Arcobacter butzleri and Arcobacter cryaerophilus in ultrahigh-temperature, pasteurized, and raw cow's milk under different temperature conditions.

Abstract: The growth and survival of Arcobacter butzleri and Arcobacter cryaerophilus in milk were investigated at different storage temperatures. Three strains of each Arcobacter species were inoculated into ultrahigh-temperature (UHT), pasteurized, and raw cow's milk and stored at 4, 10, and 20°C for 6 days. The survival of Arcobacter spp. during storage was evaluated by a culture method. Results clearly showed that A. butzleri and A. cryaerophilus remained viable in milk when stored at 4°C and 10°C for a period of 6 days. When UHT and pasteurized milk were stored at 20°C, the A. butzleri count increased, with a longer lag-phase in pasteurized milk, whereas the A. cryaerophilus count increased in the first 48 h and then rapidly decreased to below the detection limit on the sixth storage day. When raw milk was stored at 20°C, the A. butzleri and A. cryaerophilus counts decreased from the first day of storage and no viable bacteria were recovered on the last day of storage. Generally, A. butzleri displayed a significantly better growth and survival capacity than A. cryaerophilus in milk. The present study is the first to assess the survival and/or growth of A. butzleri and A. cryaerophilus in milk. The evidence suggests that in case of primary contamination of milk or secondary contamination due to postprocessing contamination, milk can act as a potential source of Arcobacter infection in humans and could have public health implications, especially for raw milk consumption.

Enumeration of Salmonellae in Table Eggs, Pasteurized Egg Products, and Egg-Containing Dishes by Using Quantitative Real-Time PCR

Abstract: Salmonellae are a major cause of food-borne outbreaks in Europe, with eggs and egg products being identified as major sources. Due to the low levels of salmonellae in eggs and egg products, direct quantification is difficult. In the present study, enrichment quantitative real-time PCR (qPCR) was employed for enumeration of salmonellae in different matrices: table eggs, pasteurized egg products, and egg-containing dishes. Salmonella enterica serovar Enteritidis and S. enterica serovar Tennessee were used to artificially contaminate these matrices. The results showed a linear regression between the numbers of salmonellae and the quantification cycle (Cq) values for all matrices used, with the exception of pasteurized egg white. Standard curves were constructed by using both stationary-phase cells and heat-stressed cells, with similar results. Finally, this method was used to evaluate the fate of salmonellae in two egg-containing dishes, long egg and tiramisu, at abused refrigeration temperatures, and results indicated the growth of bacteria over a 1-week period. In conclusion, enrichment qPCR was shown to be reliable for enumeration of salmonellae in different egg products.

Salmonella detection and aerobic colony count in deep-frozen carcasses of house sparrow (Passer domesticus) and starling (Sturnus vulgaris) intended for human consumption

Abstract: Wild birds are potential vehicles of zoonotic pathogen transmission to humans. The zoonotic concern increases for small wild birds like house sparrows ( Passer domesticus ) and starlings ( Sturnus vulgaris ) which are hunted in developing countries and commercialised in Italy for human consumption. From June to October 2011, 330 house sparrows and 140 starlings were hunted and slaughtered. Deepfrozen carcasses were transported to Italy and stored for 6-8 months at -18°C. Aerobic colony count and Salmonella detection in carcasses were assessed following standard microbiological methods (ISO 4833:2003 and ISO 6579:2004, respectively). Carcasses of house sparrows showed higher levels of aerobic bacteria in comparison to starling carcasses (5.7 vs 3.2 log10 CFU/g). Moreover, 7 out of 11 lots of carcasses of house sparrows were positive for Salmonella . Among the 18 isolates of Salmonella , 14 were S. Typhimurium, 2 were S. Enteritidis, and 2 were not distinguishable. All of them were susceptible to antibiotics. All tested carcasses of starling were Salmonella negative. Deep-freezing was not efficient as a decontamination technique on carcasses of house sparrows.

Relative Accuracy, Specificity and Sensitivity of a 5′ Nuclease Real-Time PCR Assay for Listeria monocytogenes Detection in Naturally Contaminated Pork Cuts

Abstract: In the present study, the relative sensitivity, specificity and accuracy of a real-time PCR assay for Listeria monocytogenes detection in naturally contaminated pork cuts were evaluated in comparison to the ISO 11290-1:2004 reference culture method. One hundred and sixty meat samples were collected from ten different lots over a year. The PCR method included a 24-h primary enrichment step, a DNA extraction step, and a final 5′ nuclease real-time PCR assay, including an internal amplification control (IAC) and targeting the hlyA gene. Based on the analysis of 480 sub-units (three sub-units for each sample), the relative sensitivity, specificity and accuracy of the real-time PCR assay were 77.3 %, 67.0 % and 73.1 %, respectively, corresponding to a Cohen’s kappa value of 0.69 (good agreement). Considering that real samples from the worse storage scenarios were included, these results suggest the PCR method as a rapid and accurate alternative method for the quick check of L. monocytogenes in meat lots before distribution.

Preliminary investigation on multiple-locus variable number tandem repeat analysis profiles of Listeria monocytogenes isolates from pork meat tested from packaging to fork

Abstract: Listeria monocytogenes is recognised as a public health issue and a serious challenge for the food industry. L. monocytogenes strain characterisation on the basis of serotyping and molecular typing methods is used for surveillance, epidemiological tracking and outbreak investigation purposes. Genetic variants of L. monocytogenes have diversified into four major phylogenetic lineages, with lineages 1 and 2 each containing multiple clonal groups of public health importance. Standardised tools for easy identification of clonal groups are needed to trace such groups and determine their presence in a large variety of sources. Given the current limitations of available methods for L. monocytogenes strain typing, a potentially useful approach is multiple locus variable number of tandem repeats (VNTR) analysis (MLVA). In this study, MLVA has been applied to a random group of 82 L. monocytogenes strains isolated from 8 different batches of loin chops obtained from the same facility and tested between packaging and consumption time. The strains typed were classified into 10 MLVA profiles containing a number of isolates ranging between 1 to 20. According to the identified MLVA profiles, 75.6% of the pork isolates belonged to the phylogenetic lineage 2 and serotype 1/2c, frequently associated to food isolates. However, 3 pork strains belonged to the phylogenetic lineage 1 and serotype 4b. Moreover, 17 isolates were classified in the phylogenetic lineages 2 and serotype 1/2a. Both serotypes 4b and 1/2a are frequently associated to human isolates of L. monocytogenes. These preliminary results show how the MLVA profiles can support the assessment of the risk profile of food products based on the contaminating L. monocytogenes strain types.

New technologies to enhance quality and safety of table eggs: ultra-violet treatment and modified atmosphere packaging

Abstract: In the present study the effect of ultra-violet (UV) treatment alone and in combination with 100% CO 2 modified atmosphere packaging (MAP) was evaluated both on the survival of naturally occurring bacteria, as well as on quality parameters of table eggs during 28 days of storage at 21°C. Table eggs were collected from the conveyor belt after the UV module, and placed on carton trays. A representative number of carton trays were packed in a high barrier multilayer pouch filled with 100% CO 2 . All eggs were stored at 21°C and analysed at 0, 1, 7, 14, 21 and 28 days of storage. Eggs not treated with UV and not packed were also included. On the eggshells total colony count, total coliforms and faecal coliforms counts, as well as the detection of Salmonella spp. were investigated. Moreover, chemical-functional parameters such as weight loss, albumen pH and Haugh Unit (HU) were evaluated. The total colony count on UV treated table eggs was approximately 1 log 10 CFU/g lower than untreated eggs (2.27 vs 3.29 log 10 CFU/g). During storage, CO 2 packed eggs maintained the initial values of HU, whereas the albumen pH decreased up to 1.5-2 points in comparison to unpacked eggs. The UV treatment was effective in reducing the total colony count on the surface of table eggs. MAP showed a great potential in maintaining/enhance the technological properties of egg constituents (higher foam stability of the albumen for meringue preparation) without significantly impacting on the microbial load of table eggs.