Bacteria of the three Salmonella species are sometime Gram-negative inhabitants of the intestinal tract of humans and animals. They cause a wide spectrum of infections in humans. Besides causing intestinal infections, these germs can cause typhoid fever, blood stream infections, and focal infections such as meningitis, osteomyelitis, and abscesses. Salmonella infections are divided roughly into the non-typhoid type infections, and enteric or typhoid fever type infections.

Non-typhoid Salmonella infections

The most common form of illness is characterized by fever, diarrhea, abdominal cramps and tenderness (enteritis). The incubation period is 6 to 72 hours.

The principal sources of this type of Salmonella germs are animals, including poultry, livestock, reptiles, and pets. The major routes of infection of humans are

  • foods of animal origin - poultry, red meat, eggs and unpasteurized milk
  • other foods such as fruits, vegetables, and rice
  • contaminated water
  • contact with infected animals such as pet turtles, iguanas, and snakes
  • direct person-to-person transmission via the fecal-oral route
  • contact with contaminated medications, dyes, and medical instruments

Salmonella can be deucedly difficult to get rid of. About half of infected children under 5 years will still be shedding the germ at 3 months after their initial disease. In fact, an infected individual, especially an infant, can shed the germ in the stool for up to a year or more. This naturally poses a significant danger of infection to all contacts of the infant, especially if they are not scrupulous about hand washing after handling the baby's diapers.

However, antibiotic treatment is not indicated for uncomplicated Salmonella diarrhea. It does not shorten the disease, but lengthens the time the child will carry and shed the germ. Treatment is usually reserved for babies younger than 3 months as well as persons with cancer, blood diseases such as sickle cell anemia, HIV infection or other immunosuppressive illnesses, persons on immunosuppressive therapy, and persons with chronic gastrointestinal disease, or severe colitis.

If ordinary Salmonella infection (as opposed to Salmonella typhi, the typhoid fever type) occurs in a child care setting, stool cultures and exclusion of children without symptoms is not necessary. Antibiotics are not given to persons with uncomplicated diarrhea, to those without symptoms, or those simply exposed to a child with diarrhea caused by Salmonella.

Typhoid fever

Enteric fever or typhoid fever is caused by infection with Salmonella typhi and several other Salmonella types. The illness typically starts gradually, with fever, headache, malaise, loss of appetite, lethargy, abdominal pain and tenderness, enlargement of the liver and spleen, a rash (rose spots), and sometimes even changes in mental status. Constipation may be an early symptom, with diarrhea occurring later, usually in the second week of illness.

Typhoid fever is only contracted by contact with an infected human. Cases of typhoid fever in the United States usually are acquired during foreign travel, or by consumption of food contaminated by a chronic carrier. (Perhaps you remember the story of Typhoid Mary.) The incubation period is 3 to 60 days, but usually in the range of 7 to 14 days.

Vaccination against typhoid fever is available, but the vaccines are not 100% effective in preventing disease, and can have some side effects. Thus they are reserved for those travelling to endemic areas of typhoid, for the household contacts of typhoid fever cases, and some laboratory workers who might be exposed to the germ. Luckily, outbreaks of Salmonella typhi infection are unusual in child care programs. If Salmonella typhi is identified, all the children and staff will have to be cultured and excluded until three consecutive stools culture tests are negative for Salmonella.

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