Validation of Enterococcus faecium as a surrogate for Salmonella under different processing conditions for peanuts and pecans.

Food Safety and Modernization Act (FSMA) Preventive Control rules require nut processors validate thermal processes to ensure a desirable log reduction of Salmonella is achieved. Due to the complex nature of nut and nut products, processes and equipment, it is difficult to use one validation study for all and may requires individual equipment be validated at the plant level. In plant validation studies, pathogens such as Salmonella cannot be used due to the risk of contamination, thus the suitability of a non-pathogenic organism, Enterococcus faecium as a surrogate for Salmonella was evaluated for peanut and pecan thermal processing. Stagnant and forced dry air heating conditions, (120 °C (20, 30, 40 min), 130 °C (10, 20, 30 min), 140 °C (10, 20, 30 min)) were evaluated for unblanched peanut kernels. Oil heating conditions (116 °C, 121 °C, and 127 °C for 0.5, 1.0, 1.5, 2.0, 2.5 min) were evaluated for pecan kernels. Inshell pecans are conditioned in hot or cold water to facilitate the shelling process. Water heating conditions (75 °C (20, 40, 80, 120 s), 80 °C (20, 40, 80, 120 s), 85 °C (20, 40, 80, 120 s), 90 °C (20, 40, 60, 80 s), and 95 °C (20, 40, 60, 80 s)) were evaluated for inshell pecans. Under conditions, except forced air treatment, E. faecium reductions (Log N/N0) were either not significantly different (P > 0.05) or significantly lower than Salmonella (P < 0.05), making it a suitable surrogate for the processes evaluated.

Detection of Salmonella spp. from large volumes of water by modified Moore swabs and tangential flow filtration.

This study compares the use of tangential flow filtration (TFF), normal flow filtration and modified Moore swabs (MMS) for the concentration and detection of Salmonella, spiked at 1-760 CFU l(-1), from 10 l of surface water. Two immunomagnetic separation (IMS) methods, Pathatrix and Dynabeads, for further concentration of Salmonella were compared following filtration and overnight enrichment. Detection of Salmonella by PCR, qPCR or culture-based methods was compared. TFF and MMS preformed equally well in concentrating Salmonella. MMS was able to consistently concentrate Escherichia coli O157:H7 for culture-based detection; only at the higher concentrations tested was the TFF able to consistently concentrate E. coli O157:H7 for culture-based detection. Salmonella, at population densities <10 CFU l(-1) in 10 l of spiked surface water, could be reliably (6/6) detected within 2 days by combining TFF or MMS, with IMS Pathatrix and qPCR. The theoretical limit of detection for Salmonella is considered to be sufficiently sensitive to meet all the practical screening purposes for surface waters in an agricultural setting intended for application to edible horticultural crops.

Survival and growth of Salmonella Enteritidis PT 30 in almond orchard soils.

AIMS: To evaluate factors potentially contributing to the long-term persistence of Salmonella enterica serovar Enteritidis phage type (PT) 30 in an almond orchard. METHODS AND RESULTS: Surface and subsurface soil temperatures, and air temperatures in a radiation shelter, were recorded during a 12-month period, and were used to identify relevant storage temperatures (20 or 35 degrees C) for microcosms of two different soil types (clay and sandy loams) with moisture levels near saturation or near field capacity. Salmonella Enteritidis PT 30 was inoculated into the microcosms at 6 log CFU g(-1) dry weight. Between 14 and 180 days of incubation, counts of S. Enteritidis PT 30 decreased rapidly at 35 degrees C and were significantly different (P < 0.05) from counts at 20 degrees C, regardless of the soil type or moisture level. Salmonella was detected by enrichment of 10-g samples from all microcosms after 180 days of incubation at 20 degrees C, but from none of the microcosms held at 35 degrees C. To measure the potential for the growth of S. Enteritidis PT 30 in clay loam soil, an aqueous extract of almond hulls (containing 1.6% mono and disaccharides) or equivalent volume of water was added 7 days after inoculation. Significant (P < 0.05) growth of S. Enteritidis PT 30 was observed within 8 or 24 h of adding hull extract, but not water, to soil. CONCLUSIONS: Opportunities may exist for S. Enteritidis PT 30 to survive for an extended time in almond orchard soils and to grow in these soils where hull nutrients are released. SIGNIFICANCE AND IMPACT OF THE STUDY: Temperature has a significant impact on the long-term survival of S. Enteritidis PT 30 in soil, and nutrients leached from almond hulls may result in Salmonella growth. These factors should be considered in the design of Good Agricultural Practices for almonds.

Molecular subtyping of poultry-associated type A Clostridium perfringens isolates by repetitive-element PCR.

Clostridium perfringens strains (type A) isolated from an integrated poultry operation were subtyped using repetitive-element PCR with Dt primers. Isolates were obtained from fecal, egg shell, fluff, and carcass rinse samples as part of a previously reported temporally linked epidemiological survey. A total of 48 isolates of C. perfringens were obtained from different stages of the broiler chicken production chain from two separate breeder farms that supplied a single hatchery that in turn provided chicks to a single grow-out farm whose flocks were processed at a single plant. All 48 isolates were typeable (100% typeability) by repetitive-element PCR with Dt primers. This subtyping method was highly reproducible and discriminatory. By repetitive-element PCR with Dt primers, isolates were classified into four major branches with 12 subgroups or clades. The Simpson's index of discrimination was calculated to be 0.96 for groupings of >95% correlation. Toxin gene profiles of the isolates indicated that all of the isolates were C. perfringens alpha-toxin gene positive and 46 of 48 isolates were beta2-toxin gene positive. All strains were negative for beta- and epsilon-toxin genes. Repetitive sequence-based PCR was found to be a technically practical and reproducible means of subtyping C. perfringens libraries from specific epidemiological or production environment settings.