Higher risks of food-borne illness associated with increased consumption of poultry products make it necessary to identify potential sources of contamination and apply intervention strategies that will prevent or minimize the risk of contamination during processing. This study investigated the effects of chemical and natural decontamination treatments including sprayed application of acidified calcium sulfate (ACS) in combination with -polylysine (EPL), dry-rubbing kosher salt coating and molten paraffin wax dipping application on microbial populations of broiler carcasses and parts. Treatments were evaluated for their effectiveness in reducing the numbers of artificially inoculated rifampicin resistant Salmonella Typhimurium strain NVSL 95-1776 on the skin surface of bone-in chicken breasts. General model procedures were used to find statistical differences (P<0.05) and separation of means was done with least square means using SAS 9.1. Chemical interventions (ACS + EPL) caused an overall reduction of ~0.65 CFU/ml of rifampicin resistant Salmonella Typhimurium populations in inoculated chicken breasts. Similar reductions were observed in validation experiments in whole carcasses when compared to post-eviscerated control samples as well as post chilled treated samples when compared to post-chill controls. Kosher salt interventions caused ~1.15 CFU/ml log reductions in rifampicin resistant Salmonella Typhimurium loads. Significant differences (>2 log reductions) were also observed in validation trials in both pre- and post-chilled samples when compared to non-treated pre- and post-chilled controls. Only for psychrotrophic counts, chilled and post-chill interventions did not have a significant effect (P>0.05). The use of molten paraffin wax caused <0.51 CFU/ml log reductions on rifampicin resistant Salmonella Typhimurium in chicken breasts. In addition, drip loss on kosher treated samples was 53.8% lower than non-treated counterparts. However, kosher salt application caused a decrease in lightness (*L values) and yellowness (*b values) on treated carcasses when compared to controls, redness (*a values) were not significantly affected. Results indicate that the combined use of ACS and EPL at the stated conditions and the coating application of kosher salt on broiler carcasses significantly reduce pathogen contamination and microbial indicator loads, thus providing an alternative validated antimicrobial intervention for potential use by the poultry industry.

Research has shown that Salmonella can be prevalent in poultry litter, which can be a source of contamination for newly arrived chicks at the poultry house. Since this organism is a pathogen of concern to the poultry industry, two types of litter amendments and two types of feed additions were created and tested to determine effects of broiler growth, litter moisture and efficacy against Salmonella colonization. Litter amendments consisted of the combination of acidic calcium sulfate (ACS) with either diatomaceous earth (DE) or hydrated sodium calcium aluminiosilicate (HSCAS). Feed additions consisted of differing amounts of sodium bisulfate. For the litter amendment experiments, chicks were placed into pens in isolation rooms. Each litter amendment was applied to 3 pens for replicates of experimental groups. Litter samples were taken weekly from 5 areas in each pen and combined for the determination of Salmonella cfu/g of litter. At 3 and 6 weeks post placement, birds from each pen were euthanized by CO2 asphyxiation. The crop and ceca from these birds were tested for Salmonella cfu/g of crop/ceca or presence/absence of Salmonella. Efficacy of the liter amendments varied in experimental groups on broiler growth characteristics and efficacy against Salmonella. For the determination of sodium bisulfate as a feed addition on Salmonella colonization, birds were placed into 3 experimental groups and placed into respective pens. Two sodium bisulfate experimental groups were used at 0.25% and 0.75%. The other experimental group was the control. Litter samples were taken weekly from 5 areas in each pen and combined for the determination of Salmonella cfu/g of litter, aerobic plate counts, moisture content and pH. Efficacy of the sodium bisulfate as a feed addition varied in the experimental groups on Salmonella colonization, aerobic plate counts, pH and moisture content throughout both trials.

Food irradiation is costly in terms of the energy utilized and the time spent, therefore, it is imperative to optimize it in order to avoid sub lethal dose or an overdose both of which have detrimental effects on the quality of fresh produce such as cantaloupe. The bacterial load in fresh cut cantaloupe flesh was quantified on the basis of growth and mobility over time, and used as the basis for targeted irradiation simulation. The bacterial growth was predicted using the Gompertz model, while a power law function was used for predicting the bacterial mobility. The microbiological structure of cantaloupe flesh was assessed using Transmission Electron, Scanning Electron, and Light Microscopy as a basis for understanding the mobility of the bacteria into the internal mesocarp tissues. A plate assay was also undertaken to determine the possibility of S. typhimurium producing cell wall degrading enzymes such as polygalacturonase to gain access into intact fresh cantaloupe tissues. S. typhimurium in fresh cut cantaloupe flesh has a lag phase duration of 7.76 hours and can reach a maximum population of 7.98 logs CFU/g in 30 hours. Cantaloupe flesh has a vast network of intracellular spaces through which the bacteria can move into the internal mesocarp tissues, particularly because S. typhimurium (LT2) does not produce any enzymes such as polygalacturonase which could be breaking down the cell wall binding structures as a mechanism for internalization into intact internal tissues. A theoretical bacterial inactivation dose estimate based on the experimentally determined D10-value and the bacterial population was used to simulate irradiation treatment of the cantaloupe flesh samples using a 10MeV electron beam irradiator (LINAC) to establish the best treatment. The optimal 10 MeV electron beam irradiation treatment for S. typhimurium internalized in fresh cut cantaloupe samples for 30 hours was determined to be a double beam with 0.5 cm attenuation of Lucite (Trademark) at the top and 3.3 cm at the bottom.

Human enteric pathogen Salmonella contaminates raw produce and triggers significant economic loss and illness. Under a natural environment, Salmonella resides in soil and enters the interior of plants without causing disease or eliciting symbiotic growth. Upon being consumed by humans, complex virulence mechanisms are elicited by the specific intestine conditions, such as high temperature and humidity and lead to profound infection. The lack of effective prevention and drug treatment are largely attributed to the unclear mechanistic understanding on Salmonella association with environmental media, and in vivo host and pathogen factors required for persistent infection. We have explored the potential of deploying the model plant organism Arabidopsis thaliana to tackle this fundamental yet clinically challenging question, as Arabidopsis possesses many advantages as a model system, including enriched genomic resources, powerful genetic tools, low maintenance cost and a large collection of individual gene deletion mutants. Our preliminary data demonstrated Arabidopsis seedlings under liquid culture conditions mimicking the intestine environment were infected and killed by salmonella within 2 days upon inoculation. The Arabidopsis system possesses well-developed genetic information and the resources to study host factors required for infection on very short time scales, thus complementing traditional animal genetic studies. We aim to define the pathogen factors required for this infection. By merging the fields of extremely powerful Arabidopsis genetics and bacterial genetics/genomics, we hope to provide insight into possible new paradigms for addressing salmonella-mediated food born infection.

To assess the risk factors involved in the contamination of fresh produce with human pathogenic organisms, a total of 1,257 samples were collected from cantaloupe, oranges, and parsley in the field and after processing, and the environment. Samples were collected twice in a season from two farms with operating packing sheds per commodity and analyzed for the presence of Salmonella. Sixteen, 6, and 3 isolates were obtained from irrigation water, packing shed equipment, and washed cantaloupe, respectively. Salmonella was not detected on oranges or parsley. Serotyping, pulsed-field gel electrophoresis, and repetitive sequence-based polymerase chain reaction assays were applied to Salmonella isolates to evaluate their genetic diversity and to determine if there are relationships between sources of contamination. Using PFGE, all Salmonella isolates obtained from irrigation water and equipment were determined to be different from cantaloupe isolates. Only one equipment isolate was related to isolates from irrigation water. Rep-PCR demonstrated some similarity between equipment and cantaloupe isolates, but this technique is less discriminatory. DNA fingerprinting did not conclusively determine relationships between sources of contamination. Isolates were also subjected to antimicrobial susceptibility testing using the disk diffusion method. Five out of 25 of the isolates demonstrated intermediate sensitivity to streptomycin and one isolate was resistant to streptomycin. Green fluorescent protein was an effective marker system when monitoring the survival of Salmonella on parsley as affected by processing. Dip temperature had little effect on the attachment and survival of Salmonella on parsley. Regardless of the temperature or duration of dip, Salmonella were internalized. Immersion for longer times resulted in higher numbers of attached and internalized cells. Microscopic observations agreed with these results and showed Salmonella near the stomata and within cuticle cracks. Salmonella increased over 7 storage days at 25??C and decreased at 4??C. After 7 days at 4??C, no internalized Salmonella were detected. Examination of the native microflora of parsley showed that bacterial populations were similar for parsley collected in the field and packing shed. Higher bacterial populations and fungi were observed at retail with Pseudomonas the predominant organism. Parsley supports the growth of a diverse group of microorganisms.

Salmonellae are enteric bacteria infecting animals and humans. Large animal clinics and Veterinary Teaching Hospitals are greatly affected by Salmonella outbreaks and nosocomial infection. The risk of environmental contamination and spread of infection is increased when animals are confined in close contact with each other and subjected to increased stress factors. This study was designed to compare double-enrichment culture techniques with Gel-based and Real-time PCR assays in the quest for improved diagnostic methods for detecting Salmonella in equine fecal samples. 120 fecal samples submitted to the Clinical Microbiology Laboratory of the Veterinary Medical Teaching Hospital at Texas A&M University (CML, VMTH, TAMU) were tested for Salmonella using all three techniques. Double-enrichment bacterial culture detected 29 positive results (24%), Real-time PCR detected 33 positive results (27.5%), and Gel-based PCR detected 73 positives results (60.8%). While culture and real-time PCR methods had similar results, the gel-based PCR method detected many more positive results, indicating probable amplicon contamination. Real-time PCR can be completed as soon as the day after submission while culture techniques may take 2 to 5 days to complete. However, viable bacterial cells are needed for antimicrobial susceptibility testing and serotyping: both important for epidemiological studies. Therefore, double-enrichment bacterial culture performed concurrently with real-time PCR methods could be efficient in clinical settings where both accurate and expedient results are required.

Se evaluó el efecto protectivo del uso combinado de exclusión competitiva (EC) y vacunación en gallinas de postura desafiadas experimentalmente con una cepa de campo de S.gallinarum. En dos ensayos se emplearon 200 pollitas de postura de la línea Hyline Brown de 1 día de edad provenientes de aves reproductoras libres de Salmonella sp. Para cada ensayo las aves fueron distribuídas en cinco grupos de 20 aves cada uno. En el primer ensayo, 100 aves fueron desafiadas a las 18 semanas de edad con 1 x 109 UFC/ ml de S. gallinarum y en el segundo ensayo con 1 x 10 8 UFC/ ml de la misma cepa a las 28 semanas de edad Los grupos A y C recibieron tres aplicaciones de una vacuna conteniendo la cepa 9R de S. gallinarum (Vacuna 9R) a la 4ta, 8va y 10ma semana de edad, mientras que los grupos B y D recibieron una aplicación de una vacuna inactivada de S. enteritidis en emulsión oleosa (Bacterina) a la 13va semana de edad. Adicionalmente los grupos A y B recibieron un producto de EC al día de edad en planta de incubación. En cada ensayo un grupo de aves que no recibió ninguna protección fue usado como control. El experimento se inició con la crianza de las aves en una granja comercial al norte de Lima bajo condiciones normales de manejo y bioseguridad. Las aves fueron trasladadas a la unidad experimental del Laboratorio de Patología Aviar de la FMV-UNMSM para el desafío y evaluación clínica por un periodo de observación de 22 días post reto. Fueron evaluados signos clínicos, mortalidad, lesiones, respuesta serológica y recuperación de la cepa de desafío. Para el análisis estadístico se usó la curva de supervivencia de Kaplan Meier y las diferencias estadísticas fueron evaluadas por Regresión de Cox. En ambos ensayos la mejor protección fue obtenida en los grupos vacunados con vacuna 9R sola o combinada con Exclusión competitiva (p<0.05). Diferencias estadísticas fueron observadas entre el grupo control y grupo A (vacuna 9R más EC) y grupo C (vacuna 9R). En ambos ensayos los grupos vacunados con bacterina sola o combinada con EC no fueron protegidos, no existiendo diferencias estadísticas con el grupo control (p>0.05). En el primer y segundo ensayo las aves del grupo A tuvieron una media de supervivencia significativamente diferente comparada con el grupo control y los grupos con bacterina y EC más bacterina (p<0.05). / The protective effect of the combined use of vaccination and competitive exclusion (CE) in layer hens experimentally challenged with a S. gallinarum field strain was evaluated. Two hundred Hyline Brown pullets since one day old and obtained from salmonella- free breeders were used. We divided this study in two trials in order to do two challenges in two different ages. Half of the birds were challenged at 18 weeks old (Trial 1) with 1 x 109 UFC/ ml de S. gallinarum and half remained were challenged at 25 weeks old (Trial 2) with 1 x 108 UFC/ ml . The birds were divided in five groups of 20 birds each. The groups A and C received three applications of a live Salmonella gallinarum 9R strain vaccine (9R vaccine) at 4th , 8th and 10th weeks old subcutaneously. Groups B and D received a Salmonella enteritidis oil emulsion commercial bacterine (bacterine SE) at 13 weeks old, subcutaneously. Group E unvaccinated and without competitive exclusion was the control group. The study started with the birds breed in a commercial poultry farm at the north of Lima under normal management and bio security conditions .The birds were moved to the Avian Pathology Laboratory of the College of Veterinary Medicine, San Marcos University to challenge and clinic evaluation about 22 days post-challenge. Clinical signs, mortality rates, lesions, serologic response and field strain recovery were evaluated. Kaplan Meier design and Cox regression were used to determine statistical differences. In both trials the best protection was performed in 9R vaccine groups single or combined with CE. (p<0.05). Statistical differences were observed between the control group and group A (9R vaccine plus CE) and group C (9R vaccine) .In both trials the bacterine SE vaccinated groups were not protected and there were no differences with the control group (p>0.05). In trial 1 and 2 the group A had a higher survival mean than the control group and bacterine SE group and bacterine plus CE (p<0.05).

Thesis (Ph. D.)--University of Texas at Austin, 1999. / Vita. Includes bibliographical references (leaves 149-164). Available also in a digital version from Dissertation Abstracts.

Zugl.: Berlin, Humboldt-Univ., Diss., 2008

Thesis (doctoral)--Justus Liebig-Universität Giessen, 2000.