Some Enterobacteriaceae develop a mechanism to survive in environments containing low moisture.\u00a0Salmonella\u00a0is the most frequent cause of enteric infections.\u00a0Salmonella enteric\u00a0causes \u201chigh morbidity and economic losses worldwide\u201d (Gruzdev, 2011).\u00a0The intent of this research is to investigate the survival and thermal resistance of desiccated\u202fSalmonella\u202fin low moisture foods and dry processing environments, such as peanut butter, using microbiological and molecular approaches to identify extrinsic and intrinsic factors that regulate\u00a0Salmonella\u00a0resistance and survival under long-term starvation and desiccation stresses.\u00a0<\/p>\n
Food born\u00a0illnesses\u00a0are normally associated with the ingestion of contaminated foods;\u00a0specifically,\u00a0wet foods such as milk.\u202fNon-typhoidal human salmonellosis is identified by an\u00a0\u201conset of fever, abdominal pain, nausea, diarrhea, and sometimes vomiting\u201d (\u00c1lvarez-Ord\u00f3\u00f1ez, 2011). The disease typically does not last more than a few days. Although in some instances, it may last for a longer period especially in \u201cimmunocompromised individuals, pregnant women, the elderly and children\u201d (\u00c1lvarez-Ord\u00f3\u00f1ez, 2011). A decade ago, salmonellosis was second\u00a0on the list of reported zoonotic diseases in humans. There were 108,614 confirmed cases in Europe;\u00a0Salmonella enterica\u00a0serovar Enteritidis and\u00a0S. enterica\u00a0serovar Typhimurium were the two most common (\u00c1lvarez-Ord\u00f3\u00f1ez, 2011). The most common host of\u00a0Salmonella\u00a0is the intestinal track of wild and domestic animals which leads to food\u00a0as\u00a0the driving force of infection.\u00a0Human S. Enteritidis cases are normally associated with the ingestion of contaminated egg, poultry meat and raw milk or\u00a0products (\u00c1lvarez-Ord\u00f3\u00f1ez, 2011).<\/p>\n
The reduction of moisture in foods has been a process used in foods to control the growth of bacteria in food production\u00a0(Gruzdev, 2011).\u202fHowever, there have been outbreaks of salmonellosis from the intake of dried foods. This indicates that\u202fSalmonella\u202fcan live in harsh environments in the absence of moisture for extended periods of time\u00a0(Gruzdev, 2011). Desiccated\u202fsalmonella\u202fpossesses a high tolerance to heat and ethanol.\u202fIn a study conducted by Nadia\u202fGruzdev\u202fet al., dried\u202fSalmonella enterica\u202fserotype Typhimurium cells were introduced to various stresses to examine if dehydration contributes to tolerance to other stressors.\u202fResults indicate that desiccated\u202fS.Typhimurium\u202fpossesses a greater tolerance to various stressors than\u202fnon-desiccated\u202fcells. These cells were more resistant to stressors including ethanol, sodium hypochlorite,\u202fdidecyl\u202fdimethyl ammonium chloride, hydrogen peroxide, NaCl, bile salts, dry heat, and UV radiation\u00a0(Gruzdev, 2011). In the presence of acetic acid and citric acid, the rate of survival reduced in the desiccated calls in comparison the\u202fnon-desiccated\u202fcells. There are three other serotypes in\u00a0S.\u202fenterica\u202fthat demonstrated stress responses such like\u202fS.Typhimurium; S. Newport, S.\u202fInfantis, and S. Enteritidis\u00a0(Gruzdev, 2011). In contrast, S. Hadar was more\u202fvulnerable\u202fand could only tolerate a small number of stressors. This concluded that dehydration causes cross-tolerance to several stresses in S. enterica, indicating the restriction of treatments used by the food industry to deactivate food-borne pathogens\u00a0(Gruzdev, 2011).\u202f\u00a0<\/p>\n
The first outbreak of salmonellosis related to the ingestion of peanut butter was reported in 1996. A study by Burnett et al. was conducted to determine characteristics of survival of high and low inoculation of a five-serotype blend of\u202fSalmonella\u202fin five commercial peanut butters and 2 commercial\u202fpeanut\u202fbutter spreads. A similar study conducted by Park et al. was performed on peanut butter in Tennessee. Park et al. used an inoculation of a 3-strain blend of 5 commercial brands of peanut butter. Both studies found that the products initially inoculated with\u00a0Salmonella\u00a0were found positive for the pathogen after storing the product at 4-5\u00b0C for 24 weeks; except for natural peanut butter. However, products stored at 21-22\u00b0C did not show traces of\u00a0Salmonella\u00a0after storage following 24 weeks\u00a0(Burnett, 2000). Results of this study indicate that\u00a0Salmonella\u00a0survives in peanut butter and peanut butter spread for\u202fa\u202fminimum of 24 weeks at 5\u00b0C and potentially 21-22\u00b0C; or for the duration of their shelf life\u00a0(Park, 2008).\u00a0Salmonella\u00a0in the products can be caused by post-process contamination while repackaging or use as an ingredient in other food product which are not protected against contamination from the pathogen. This can lead to its existence at the time of ingestion\u00a0(Burnett, 2000).\u202f\u00a0<\/p>\n
Before 1970s, eggs that were not handled in a sterile fashion often corresponded to food borne illnesses\u00a0(Jones, 1995). It was not until the passage of the Egg Product Sanitation Act in 1970 that contaminated egg production decreased (Jones, 1995).\u00a0A study conducted by Jones et al. was done\u00a0is to examine which egg, egg contents, and egg production facilities are contaminated with Salmonella. Egg samples were taken from different stages of an egg processing operation as well as from the production facility. Salmonella was recovered from ventilation fan, egg belt and flush water. Salmonella was detected on 7 put of the 90 eggshells sampled prior to processing and 1 out of 90 eggshells sampled following processing. There was only 1 eggshell found positive for Salmonella which was likely due to a low pH of the water sample. However, Salmonella<\/em> was not found in the 180 eggs examined for internal contamination after processing. The 60 isolates from the production facilities\u00a0included Salmonella \u202fserotypes:\u202fS.\u202fagona,\u202fS.typhimurium, S.\u202finfantis,\u202fS.derby, S.\u202fheidelberg, S.\u202fcalifornia, S.\u202fmontevideo, S.\u202fmbandaka,\u202fand\u202funtypable\u00a0(Jones, 1995). This report suggests that Salmonella is a common inhabitant of egg production facilities\u00a0(Jones, 1995). In order to determine the true percentage of eggs infected with Salmonella, more eggs should be examined. However, based on the data, only a small percentage of eggs contain liquid contents contaminated with\u202f Salmonella.\u202f<\/p>\n In a study to test non-thermal inactivation of\u00a0Salmonella enteritidis\u00a0in a food model system supplemented with a natural antimicrobial,\u00a0taramasalad, a popular Greek appetizer, was used. It was first inoculated with\u00a0S. enteritidis\u00a0in addition to different concentrations of oregano essential oil and stored at different temperatures (5, 10, 15, 20\u00b0C). Lemon juice was added to adjust the pH from 4.3 to 5.3. In order to estimate the kinetic parameters of the pathogen, bacterial counts were \u201cmodeled as a function of time\u00a0(Koutsoumanis, 1999).\u201d Two models were used for comparison. Depletion of Salmonella was evident in all cases and\u202fpH,\u202fstorage temperature, and oil concentration were the determinants for the death rate\u00a0(Koutsoumanis, 1999). The three factors were used to predict the death of S. enteritidis in homemade\u202ftaramasalad.\u202f\u202f\u00a0<\/p>\n Products that are have low-water activity such as peanut butter, infant formula, chocolate, cereal products, and dried milk do not typically support the development of vegetative pathogens such as Salmonella. (Podolak, 2010) Instead, contamination of Salmonella in these products are from \u201cpoor sanitation practices, poor equipment design and poor ingredient control\u201d\u00a0(Podolak, 2010). Reduction of Salmonella is affected by factors such as storage temperature and formulation of the product\u00a0(Podolak, 2010). Heat resistant Salmonella is dependent on the serotypes tested, growth and storage conditions prior to testing, media used to test, media used for the recovery of heat-damaged cells and chemical and physical composition. Reduction of moisture results in the increase of Salmonella resistance to heat\u00a0(Podolak, 2010).\u00a0<\/p>\n A study conducted by Jung et al. was performed to determine if a four-strain blend of multidrug-resistant Salmonella typhimurium definitive type 104 cells and a four-strain blend of S. typhimurium non-DT104 cells varied in survival mechanism in whole egg powder. Corn syrup solids and salt, egg yolk powder was also added to the egg powder. Items were stored in 13 or 37\u00b0C\u00a0for 8 weeks. Results indicate that there was no significant difference in the rates of inactivation of DT104 and non-DT104 cells. Both DT104 and non-DT104 cell types were found in egg white powder containing 4.9% moisture while in 54\u00b0C\u00a0for one week. Heating at 82\u00b0C\u00a0did not eradicate S. typhimurium in white powder (Jung, 1999).\u00a0<\/p>\n A research conducted by Finn et al. was done to examine the phenotypic characterization of Salmonella isolated from food production environments associated with low-water activity food. An examination of Salmonella growth in 18 serotypes in NaCl,\u00a0KCl, and glycerol determined that \u201cglycerol was the least inhibitory\u201d amongst the three humectants (Finn, 2013). This proved that there is a link between the ability to subsist in\u00a0KCl\u00a0and biofilm formation. This information is significant especially for food safety as well as the safety of the public\u00a0(Finn, 2013).\u00a0<\/p>\n To study the environmental conditions that affect Salmonella survival after dehydration and cold storage, Gruzdev et al. used a 96-well polystyrene plate model. It was determined that the SL 1344 strain displayed a higher level of survival in comparison with the other Typhimurium isolates and S. enterica serotypes (Gruzdev, 2012). Desiccation of this strain also suggested that \u201ctemperature, stationary-phase of the growth, solid medium, and the presence of increasing NaCl concentrations in growth medium enhanced desiccation tolerance\u201d (Gruzdev, 2012). \u00a0Desiccated Salmonella was able to survive over 100 weeks at 4\u00b0C. When a viability staining was performed, it revealed a \u201c50% reduction in viable cells\u201d (Gruzdev, 2012). These findings suggest that bacteria transitions into a \u201cviable-but-not-cultivable state (VBNC)\u201d (Gruzdev, 2012). When chloramphenicol is added, it reduces survival in bacteria which may suggest that \u201cadaptation to desiccation stress required de-novo protein synthesis\u201d (Gruzdev, 2012).\u00a0 This means that a shorter dehydration time equals a lower survival. This study focuses on how desiccated Salmonella in the food industry is impacted by the conditions in the environment.<\/p>\n Foods preserved in dry environments typically have a longer shelf life and\u202fhave the ability to\u202flast for years. Foods that are low in moisture are considered to have a reduced \u201cwater activity\u201d\u00a0(Finn, 2013). The accessibility of moisture for biological reactions can be lowered by taking proper precautions such as freeing, spray drying, or by adding solutes such as sugar and salt\u00a0(Finn, 2013).\u00a0Reducing the\u202faw\u202fis a great preserving method however, microorganisms can still survive this phase (Finn, 2013). Spores and vegetative cells can survive for months to years in dried foods. Once a dry food production environment is contaminated by a microorganism, it is difficult to remove the bacterium (Finn, 2013). An example of a method used in high moisture foods to reduce microorganisms but cannot be used in low moisture foods is mild heat treatment and high pressure (Finn, 2013). The same methods used for high moisture foods should be\u00a0different from the methods used for low moisture foods. The contamination of\u202fSalmonella\u202fin a dry food production can spread in the presence of water. This allows the growth and spread of the organism causing contamination. It is advised that in processing environments, the use of wet cleaning should be limited because it can spread contamination unless it is necessary (Finn, 2013).<\/p>\n \u00c1lvarez-Ord\u00f3\u00f1ez, A., Begley, M., Prieto, M., Messens, W., L\u00f3pez, M., Bernardo, A., & Hill, C. (2011). Salmonella spp. survival strategies within the host gastrointestinal tract.\u00a0Microbiology<\/em>,\u00a0157<\/em>(12), 3268\u20133281. doi: 10.1099\/mic.0.050351-0<\/p>\n Burnett, S., Gehm, E., Weissinger, W., & Beuchat, L. (2000). Survival of\u00a0Salmonella\u00a0in peanut butter and peanut butter spread.\u202fJournal of Applied Microbiology,\u202f89(3), 472\u2013477.\u00a0doi: 10.1046\/j.1365-2672.2000.01138.x\u00a0<\/p>\n Finn, S., Condell, O., McClure, P., Am\u00e9zquita, A., & Fanning, S. (2013). Mechanisms of survival, responses and sources of Salmonella in low-moisture environments. Frontiers in microbiology, 4, 331. doi:10.3389\/fmicb.2013.00331\u00a0<\/p>\n Finn, S., Hinton, J. C. D., Mcclure, P., Am\u00e9zquita, A., Martins, M., & Fanning, S. (2013). Phenotypic Characterization of Salmonella Isolated from Food Production Environments Associated with Low\u2013Water Activity Foods. Journal of Food Protection, 76(9), 1488\u20131499.\u00a0doi: 10.4315\/0362-028x.jfp-13-088\u00a0<\/p>\n Gruzdev, N., Pinto, R., &\u202fSela, S. (2011). Effect of Desiccation on Tolerance of Salmonella\u202fentericato\u202fMultiple Stresses.\u202fApplied and Environmental Microbiology,\u202f77(5), 1667\u20131673.\u202fdoi: 10.1128\/aem.02156-10.\u202f\u00a0<\/p>\n Gruzdev, N., Pinto, R., & (Saldinger), S. S. (2012). Persistence of Salmonella enterica during dehydration and subsequent cold storage.\u00a0Food Microbiology,\u00a032(2), 415\u2013422.\u00a0doi: 10.1016\/j.fm.2012.08.003\u00a0<\/p>\n Jones, F. T., Rives, D. V., & Carey, J. B. (1995). Salmonella Contamination in Commercial Eggs and an Egg Production Facility.\u202fPoultry Science,\u202f74(4), 753\u2013757.\u202fdoi: 10.3382\/ps.0740753\u202f\u00a0<\/p>\n Koutsoumanis, K.,\u202fLambropoulou, K., &\u202fNychas, G.-J. (1999). A predictive model for the non-thermal inactivation of Salmonella enteritidis in a food model system supplemented with a natural antimicrobial.\u202fInternational Journal of Food Microbiology,\u202f49(1-2), 63\u201374.\u202fdoi:\u00a010.1016\/s0168-1605(99)00054-9\u202f\u00a0<\/p>\n Park, E.-J., Oh, S.-W., & Kang, D.-H. (2008). Fate of Salmonella Tennessee in Peanut Butter at 4 and 22 \u00b0C.\u202fJournal of Food Science,\u202f73(2).\u00a0doi: 10.1111\/j.1750-3841.2007.00638.x\u00a0<\/p>\n Podolak, R., Enache, E., Stone, W., Black, D. G., & Elliott, P. H. (2010). Sources and Risk Factors for Contamination, Survival, Persistence, and Heat Resistance of Salmonella in Low-Moisture Foods. Journal of Food Protection, 73(10), 1919\u20131936.\u00a0doi: 10.4315\/0362-028x-73.10.1919\u00a0<\/p>\n Jung, Y., & Beuchat, L. (1999). Survival of multidrug-resistant Salmonella typhimurium DT104 in egg powders as affected by water activity and temperature. International Journal of Food Microbiology, 49(1-2), 1\u20138.\u00a0doi: 10.1016\/s0168-1605(99)00013-6\u00a0<\/p>\n","protected":false},"excerpt":{"rendered":" The intent of this research is to investigate the survival and thermal resistance of desiccated\u202fSalmonella\u202fin low moisture foods and dry processing environments.<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[12],"tags":[],"class_list":["post-2890","post","type-post","status-publish","format-standard","hentry","category-essaysbiology"],"yoast_head":"\nWorks Cited<\/h2>\n