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Intoxications and infections caused by food borne pathogens represent increasing public health problems. Food poisoning is wide variety of diseases which are by eating food which has been contaminated and with pathogenic microorganisms. Food poisoning is caused by small and certain bacteria that grow and multiply which slowly start to case food poisoning. (Money et al. 2010). In 1992, the chief medical officer defined food poisoning as "Any disease of an infectious or toxic nature caused by or thought to be caused by or thought to be caused by the consumption of food or water" (Eley A.R, 1996) . Food poisoning is a worldwide issue as pathogens are spreading worldwide and threats of new borne diseases are occurring. This can be through globalization of food supply, the inadvertent introduction of pathogens into new geographic areas, through travellers, refugees, and immigrants exposed to unfamiliar food-borne hazards abroad. (WHO, 2002). Food poisoning can be caused due to many reasons as already mentioned. The pathogen inside the human body begins to multiply and symptoms occur. Most symptoms due to food symptoms occur gradually. There is an incubation period where food poisoning starts to develop. This is an incubation period of 1-3 days. Most common symptoms associated are nausea, vomiting, diarrhoea, loss of appetite, high temperature, stomach cramps. There are other symptoms associated with food poisoning and this could vary on the pathogen causing the food poisoning. (Eley, R. A, 1992)
For food poisoning to occur, bacteria required warmth and moisture to grow, they begin to multiply as they reproduce. Contamination of food occurs rapidly and bacterial cells continue to multiply. The UK Food agency's are finding strategies to reduce food poisoning and are being tested in five different bacteria; Salmonella, Campylobacter, Listeria, Escherichia coli O157 and Clostridium perfringens. In this literature review the pathogens that have been studied are Salmonella, Listeria and Escherichia coli O157.
The genus Salmonella is in the family of Enterobacteriaeae. It is a gram-negative facultative rod-shaped bacterium which causes a microbial infection. This pathogen is mostly associated with food poisoning incidences. Non-typhoid salmonella causes gastrointestinal infection which is being effected worldwide. Studies suggest that salmonella has been estimated to cause 1.4 million infections. (Voetsch et al. 2004). In humans, salmonella is the cause of two diseases; salmonellosis which is also known as enteric fever (typhoid), which results from bacterial invasion of the bloodstream. And the other disease caused by salmonella is acute gastroenteritis; this results from a food borne infection. Salmonella is developed after eating food which is contaminated with Salmonella bacteria. Food such as; eggs, minced meat, chicken, dairy products, desserts which contain cream, sandwich fillings and processed food. Salmonella bacteria can be killed from 66 degrees Celsius and do not grow below 4 degrees Celsius. The incubation period is approximately 12-36 hours, and symptoms such as fever, abnormal pains, diarrhoea and vomiting start to occur. This infection is common, in the EU, it has been confirmed 131,468 cases during 2008 (EFSA, 2008). In 2008, a study was carried to see the effects of Salmonella, there were volunteers and results suggested that 'the frequency of illness depends on the magnitude of exposure' and it was concluded that salmonella is a highly infectious and that the risk of illness increases with the higher doses in infected subjects. (Peter F. et al. 2010).
Escherichia coli is a part of the family Enterobacteriaeae as well as Salmonella. It is a gram negative rod and causes diseases to humans and animals. There are two types of bacteria which cause diseases; Enterotoxigenic Escherichia coli is described as being responsible for traveller's diarrhoea. (Jiang, G, et al, 2002). This type of bacterial infection is low in the UK. The other common type of Escherichia coli is Enterhaemorrhagic which includes the Escherichia coli O157a zoonotic pathogen. This pathogen is responsible for food poisoning outbreaks annually. It causes bloody diarrhoea, haemolytic uremic syndrome. Escherichia coli O157 is able to grow and survive in different conditions; water, soil, sewage and even metal surface. These growth factors are affected by temperature, pH, competition with soli and environmental conditions (Jiang et al. 2002). This bacterium is able to survive for long period of time in water and in cold temperatures (Eley, R. A, 1992).Â The bacterium is able to infect people through contaminated foods such as meat, vegetables and water supplies. It can also infect people through contact with animals such as cattle and sheep. Studies have come to show that the majority of the infection occurred of Escherichia coli O157 where in the warmest time of the year in the UK which comes to the months of July, August September. Suggesting that this study shows that Escherichia coli infection is able to grow and cause infections to humans and warmer temperatures. A study was carried out to see if the weather conditions effect the growth and infection of Escherichia coli. The study suggest that the weather conditions and the number of private water supplies contribute to the infection rate of Escherichia coli O157 in Scotland, England and Wales. (Money et al, 2010).
Listeria Monocytogenes is also a bacterial food poisoning pathogen which are gram positive, facultaively anaerobic, non spore-forming bacilli. Listeria Monocytogenes is a pathogen which causes Listeriosis. This pathogen causes serious infection and illness to the human. This pathogen is different from Salmonella and Escherichia coli as it grows in normal refrigeration temperatures. Listeria pathogen can be caused from farm fields, vegetables, animals, food processing environment supermarkets and at home. (Eley, R. A (1992).Â The infection caused by this pathogen causes very high cases of food poisoning in the United states, a high mortality rate of 43% of food poisoning deaths. (CDC, 2006).
Final Project will be taken out using techniques such as aseptic techniques and PCR to determine the effects and the difference in the 3 pathogens mentioned above. A recent studied used Real-Time PCR to carry out diagnostic tests for rapid identification of food contamination caused by the pathogens, Salmonella, Escherichia coli O157 & Listeria. A multiple PCR-based platform for detection of milk associated with the 3 mentioned pathogens. A screening of several milk samples was tested and results were that 1 CFU was counted in 25 ml aliquots of raw milk in duration of 2 days. (Omiccioli, E., et al, 2009). The final project that will be carried out in the final year will use the aseptic technique and possibly a PCR in order to determine the differences between the 3 pathogens as already mentioned.