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Salmonella is the common name given to a type of food poisoning caused by the bacteria called Salmonella enteritidis (other types of illnesses are caused by other species of Salmonella bacteria, including typhoid fever). When people eat food contaminated by S. enteritidis, they suffer from inflammation of hte stomach and intestines, with diarrhea and vomiting resulting. This illness is called gastroenteritis.

Salmonella food poisoning is most often caused by improperly handled or cooked poultry or eggs. Because chickens carrying the bacteria do not appear at all ill, infected chickens go on to lay eggs or to be used as meat.

Early in the study of Salmonella food poisoning, it was thought that Salmonella bacteria were only found in eggs which had cracks in them. It was thought that the bacteria existed on the outside of the eggshell, and could only find their way in through such cracks. Stringent guidelines were put into place to ensure that cracked eggs do not make it to the marketplace, and to make sure that the outside of eggshells are all carefully disinfected. However, outbreaks of Salmonella poisoning continued. Research then ultimately revealed that, because the egg shell has tiny pores, even uncracked eggs which have been left for a time on a surface (such as a chicken's roost) contaminated with Salmonella could become contaminated. Subsequently, further research has demonstrated that the bacteria can also be passed from the infected female chicken directly into the substance of the egg prior to the shell forming around it.

Currently, the majority of Salmonella food poisoning occurs due to unbroken, disinfected grade A eggs, which have become infected through bacteria which reside in the hen's ovaries. In the United States, he highest number of cases of Salmonella food poisoning occur in the Northeast, where it is believed that about one out of 10,000 eggs is infected with Salmonella.

The only way to avoid Salmonella poisoning is to properly cook all food which could potentially harbor the bacteria. Neither drying nor freezing are reliable ways to kill Salmonella; only sufficient heat can be trusted to kill Salmonella. While the most common source for human infection with Salmonella bacteria is poultry products, other carriers include pets such as turtles, chicks, ducklings, and iguanas. Products which contain animal tissues may also be contaminated with Salmonella.

While anyone may contract Salmonella food poisoning from contaminated foods, the disease proves most threatening in infants, the elderly, and individuals with weakened immune systems. People who have had part or all of their stomach or their spleen removed, as well as individuals with sickle cell anemia, cirrhosis of the liver, leukemia, lymphoma, malaria, louse-borne relapsing fever, or acquired immunodeficiency syndrome (AIDS) are particularly susceptible to Salmonella food poisoning. In the United States, about 18% of all cases of food poisoning are caused by Salmonella.

Salmonella food poisoning is diagnosed by examining a stool sample. Under appropriate laboratory conditions, the bacteria in the stool can be encouraged to grow, and then processed and viewed under a microscope for identification.

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