According to the U.S. Centers for Disease Control and Prevention (CDC), there are approximately 40,000 reported cases of infections caused by salmonella every year. Because many cases are not even reported, the CDC estimates that the true number of infections could be more than 1 million. People with impaired immune systems, the elderly and young children face the highest risk, especially children younger than 5 years old. Each year, this bacterium causes 400 deaths.
Bacteria Type
Salmonella is a gram negative rod bacterium. Microbiologists use a staining process as one way of classifying bacteria. Salmonella is gram negative because it does not keep the first stain that is used in this staining process, called a gram stain. The word "rod" refers to the shape of the bacterium. Warren Levinson, M.D., Ph.D., professor of microbiology at the University of California explains in "Review of Medical Microbiology and Immunology," that there are three species of salmonella: S. enteritidis, S. typhi, and S. choleraesuis.
Gastroenteritis Characteristics
Gastroenteritis is the inflammation of the mucous membrane of the stomach and the intestines. Burke Cunha, M.D., professor of medicine at the State University of New York writes in "The Merck Manual for Healthcare Professionals" that this infection is usually contracted by eating eggs, raw milk, poultry or meat that has been contaminated by Salmonella enteritidis. Symptoms typically appear 12 to 48 hours after eating the contaminated food. The symptoms include fever, abdominal pain, nausea and vomiting, and a watery diarrhea. At times, there may be bloody diarrhea, but it is usually watery. Symptoms usually last no more than four days.
Osteomyelitis
Osteomyelitis is inflammation of the bone, a characteristic of salmonella that appears when infection spreads to bone that is near infected tissue. Diabetics can get osteomyelitis in this way. Staphylococcus aureus causes most of the infections. Bacteria can also spread through the bloodstream. People who suffer from sickle cell anemia get osteomyelitis from salmonella traveling through the bloodstream to reach the bone. They have fever and bone pain. The infected area will feel warm, and may look red and swollen.
Septicemia
Levinson writes in "Review of Medical Microbiology and Immunology" that salmonella can cause infections by traveling through the bloodstream in people who have cancer and in children who have enterocolitis, the inflammation of the small and large intestines. It usually leads to pneumonia and meningitis, but the bacteria can infect any damaged tissues as well as any grafts that have been placed on blood vessels. Salmonella choleraesuis is responsible for most of these infections.
Typhoid Fever
Typhoid fever is caused by Salmonella typhi. According to Dr. Cunha in "The Merck Manual for Healthcare Professionals," there are still 400 to 500 cases of this disease every year. Most of the cases are from people who traveled abroad to countries where the disease is prevalent. The infection starts in the intestines, but the bacteria enters the lymph nodes and the bloodstream. The liver, spleen and gallbladder then become infected. The symptoms are headache, fever, abdominal pain, and usually constipation.
References
- U.S. Centers for Disease Control and Prevention: Salmonellosis
- "Review of Medical Microbiology and Immunology," Warren Levinson, M.D., Ph.D.; 2008
- "The Merck Manual for Healthcare Professionals": Salmonella Infections
