In approximately 5% of nontyphoidal Salmonella infections, patients develop bacteremia. In a small proportion of those cases, the bacteria can cause a focal infection, where it becomes localized in a tissue and causes an abscess, arthritis, endocarditis, or other severe illness. Infants, the elderly, and immune-compromised persons are at greater risk for bacteremia or invasive disease. Additionally, infection caused by antimicrobial-resistant nontyphoidal Salmonella serotypes appears to be more likely to cause bloodstream infections.
Overall, approximately 20% of cases each year require hospitalization, 5% of cases have an invasive infection, and 0.5% die. Infections in infants and in people 65 years of age or older are much more likely to require hospitalization or result in death. There is evidence that Salmonella infections increase the risk of developing digestive disorders, including gastroesophageal influx disease and irritable bowel syndrome (IBS). In a retrospective matched case control study of military medical records, Porter et al. analyzed the increased risk of chronic gastrointestinal sequelae following infection with four foodborne pathogens including Salmonella. Results are shown in Table 4 below.
Although most persons who become ill with diarrhea caused by Salmonella recover without any further problems, a small number of persons develop a complication often referred to as reactive arthritis. The terminology used to describe this type of complication has changed over time. The term “Reiter Syndrome” was used for many years, but has now fallen into disfavor. The precise proportion of persons that develop reactive arthritis following a Salmonella infection is unknown, with estimates ranging from 2 to 15%. Symptoms of reactive arthritis include inflammation (swelling, redness, heat, and pain) of the joints, genitourinary tract (reproductive and urinary organs), or eyes.
More specifically, symptoms of reactive arthritis include pain and swelling in the knees, ankles, feet, and heels. Less frequently, the upper extremities may be affected, including the wrists, elbows, and fingers. Tendonitis (inflammation of the tendons) or enthesitis (inflammation where tendons attach to the bone) can occur. Other symptoms may include prostatitis, cervicitis, urethritis (inflammation of the prostate gland, cervix, or urethra), conjunctivitis (inflammation of the membrane lining the eyelid), or uveitis (inflammation of the inner eye). Ulcers and skin rashes are less common. Symptoms can range from mild to severe.
Reactive arthritis typically occurs anywhere from three days to six weeks after the antecedent infection and may involve one or more joints, though usually six or fewer. Although most cases recover within a few months, some continue to experience complications for years. Treatment focuses on relieving the symptoms.
There are a lot of gaps in our knowledge surrounding this complication. Since there is no specific test for reactive arthritis, doctors rely on signs and symptoms of the patient to make the diagnosis. However, there are no clearly defined criteria or set of symptoms used to diagnose this condition. The role of genetics is also unclear. It is thought that the presence of a gene called human leukocyte antigen, namely HLA-B27, predisposes a person to develop reactive arthritis, along with other autoimmune diseases; however, several studies have shown that many persons that develop reactive arthritis lack this genetic factor.