Complications
Patients with Salmonella gastroenteritis may develop a reactive arthritis near the time of the gastrointestinal symptoms. This is an immune phenomenon and does not require specific antibiotic therapy. Extraintestinal spread to the joints must be considered, but this is usually more localized.
Reactive arthritis usually involves the lower limbs in an oligoarticular pattern.
This may be a short-term complication or may be more chronic. The mean timeframe for resolution is usually a few months; one report found that just over one-half of patients were still symptomatic after 6 months.[130]
Bacteremia is estimated to occur in 3% to 10% of laboratory-confirmed cases of salmonellosis.[59] However, this is likely an overestimate due to detection bias; the overall rate of bacteremia in Salmonella infections is probably <5%. In nontyphoidal salmonella invasive disease, bacteremia progressing to septicemia is the most prevalent complication, followed by anemia.[124]
Nontyphoid bacteremia in the absence of severe gastroenteritis should suggest either immunosuppression or, in older patients, an infected atherosclerotic aneurysm. The incidence of nontyphoidal Salmonella bacteremia rises with age and in association with specific serotypes such as S Typhimurium, S Enteritidis, and S Heidelberg.[125] In contrast, the peak incidence of bacteremia with the enteric fever serotypes S Typhi and S Paratyphi A is seen in children and young adults.[125][126]
Two sets of blood cultures should be ordered in patients with fevers or systemic signs of bacteremia.
Treatment involves intravenous antibiotic therapy, generally for 7 to 14 days' duration.[44] Empiric therapy for life-threatening bacteremia can include a third generation cephalosporin and a fluoroquinolone until susceptibilities are available.[44] Patients should undergo repeat blood cultures to assure clearance.[43] Patients with HIV with Salmonella bacteremia are typically treated for 4 to 6 weeks to decrease the risk of recurrent infection.[44]
Spread of Salmonella outside of the gastrointestinal tract may result in endovascular or localized infections in the bones, joints, or other locations. Salmonella is a cause of aortitis, a potentially lethal complication, particularly in adults over 50 years old.[127] Neurologic involvement with meningitis may also occur, predominantly in children. The likelihood of extraintestinal disease is higher among patients with underlying medical conditions such as sickle cell anemia or T-cell or other immune deficiencies. A high index of suspicion for endovascular infections should be maintained, especially among patients with risk factors.[128] A simple scoring algorithm has been developed to identify patients with nontyphoidal Salmonella bacteremia who are at high risk of an endovascular infection.[129]
Physicians should be aware of these potential complications and should obtain blood cultures and imaging among patients with persistent or recurrent fevers or signs of extraintestinal involvement.[65] For example, patients with persistent or high-grade bacteremia (>50% of 3 or more blood cultures) or risk factors for endovascular complications should undergo imaging to exclude these complications. Imaging techniques may include echocardiography of the heart to rule out vegetations, as well as computed tomography (CT) scans or indium-labeled white blood cell-tagged studies to look for other sites of endovascular involvement. Patients with symptoms consistent with meningitis should have central nervous system (CNS) imaging and a lumbar puncture performed. Muscle involvement can be detected using imaging such as CT scans, and bony involvement, with bone scans or CT/magnetic resonance imaging scans.
Patients should initially receive intravenous antibiotics. The course of therapy depends on the location of the infection and the clinical response to therapy. Intravenous antimicrobial therapy for endovascular infections (e.g., infected aneurysm) is generally continued for a minimum of 6 weeks after successful surgery, followed by oral antibiotics. Commonly, surgical management is also necessary (e.g., drainage of a Salmonella muscle abscess or a valve replacement in cases of endocarditis).
Infections of the CNS or endocarditis may be life-threatening. For instance, Salmonella CNS infections, which most commonly occur in children, may have a mortality of nearly 50%.[43] Early diagnosis and institution of therapy with appropriate antibiotic (to which the isolate is sensitive) and surgical management improve survival.
Fevers unresponsive to current therapy should prompt consideration for an isolate with resistance to the current therapy. Sensitivity testing should be checked and antibiotics adjusted accordingly.
In addition, extraintestinal disease, such as a localized infection that has not been appropriately drained or debrided, may cause a persistent fever.
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