Salmonella

 

Salmonella is a genus of rod-shaped bacteria. 

More than 1,500 species have been identified, usually isolated from the intestinal tract of humans and animals.  Salmonella organisms are responsible for human gastrointestinal tract diseases known as salmonelloses, which range from fairly mild attacks of fever, diarrhea, vomiting, and abdominal cramps to life-threatening illness if the bacteria cause excessive dehydration or spread to other organs.

 

Outbreaks may occur from eating meat from animals with strains of Salmonella made resistant by excessive use of antibiotics in the feed.  Salmonella infections caused by improper food handling or unsanitary conditions include food poisoning and typhoid fever.  The bacteria have been found often in chicken and eggs since the late 1980s.

 

 

   

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Symptoms

The incubation period for salmonellosis, i.e. the time in between ingestion and the onset of the first symptom, may be from 6 hours to 10 days, but usually falls between 6 hours and 48 hours.1 Salmonella causes a gastroenteritis; persons experience diarrhea, often with fever and abdominal cramps. The onset may be sudden and there may be nausea and vomiting initially. The diarrhea often includes mucous and is occasionally bloody.

Infants, the elderly, immune suppressed persons and persons with sickle cell anemia are most susceptible to disease and suffer the most severe symptoms. It is in these individuals that the organism is most likely to gain access to the blood stream and possible persist in sites of the body distant from the intestine, such as on the aorta or in bone.

Risks

Persons with diarrhea usually recover completely, although it may be several months before their bowel habits are entirely normal. A small number of persons who are infected with Salmonella will go on to develop pains in their joints, irritation of the eyes, and discomfort on urination. This is called Reiter's syndrome or reactive arthritis and starts a few weeks after the gastroenteritis. It can last for months or years, and can lead to chronic arthritis that may be difficult to treat. Antibiotic treatment does not make a difference in whether or not the person later develops Reiter's syndrome. Salmonella is rarely fatal; the fatality rate is much less than one percent. It is the very young, the very old, and the very immunocompromised that are at risk for death.

Detection

The diagnosis of salmonellosis is confirmed by cultures of stool or blood. In other words, specimens of blood or faeces are placed in nutrient broth or on agar and incubated for 2-3 days. After that time, a trained microbiologist can recognize Salmonella bacteria if present by its unique characteristics.

However, blood cultures are often not performed and in most cases the blood stream is not infected. In the stool, the laboratory is challenged to pick out Salmonella from many other similar bacteria that are normally present. In addition, many persons submit cultures after they have started antibiotics, which may make it even more difficult for a microbiology lab to grow Salmonella. So, the diagnosis of salmonellosis may be problematic and many mild cases are culture negative.

Prevention

In order to stop the increasing numbers of cases of Salmonella, consumers and producers must be educated on proper handling and cooking of eggs and other high-risk foods. Quick reporting and cooperation between all local, state and federal agencies are critical in identifying outbreaks, so fewer people are affected once foodborne outbreaks occur.

Cross-contamination of foods must be avoided. Uncooked eggs, poultry and meats should be kept separate from produce and ready-to-eat foods. Hands, cutting boards, counters, knives, and other utensils should be washed thoroughly after handling uncooked foods. Hands should be washed before handling any food, and between handling different food items.