INTRODUCTION — Salmonellae are motile gram-negative bacilli that infect or colonize a wide range of mammalian hosts. They cause a number of characteristic clinical infections in humans, including:
●Gastroenteritis
●Enteric fever (systemic illness with fever and abdominal symptoms)
●Bacteremia and endovascular infection
●Focal metastatic infections such as osteomyelitis or abscess
●An asymptomatic chronic carrier state
Enteric fever is caused by Salmonella typhi and Salmonella paratyphi. The pathogenesis, microbiology, epidemiology, clinical features, and treatment of these infections are discussed elsewhere. (See "Pathogenesis of enteric (typhoid and paratyphoid) fever" and "Enteric (typhoid and paratyphoid) fever: Epidemiology, clinical manifestations, and diagnosis" and "Enteric (typhoid and paratyphoid) fever: Treatment and prevention".)
Other Salmonella serotypes are collectively known as nontyphoidal salmonellae. Nontyphoidal salmonellae are frequently isolated from the stool of patients with gastroenteritis. The major issues involved in the clinical approach to the finding of nontyphoidal Salmonella in a stool culture will be reviewed here.
Detailed discussion of the microbiology and epidemiology of nontyphoidal salmonellae as well as the clinical features and treatment of extraintestinal infection with nontyphoidal salmonellae are found elsewhere. (See "Pathogenesis of Salmonella gastroenteritis" and "Nontyphoidal Salmonella: Microbiology and epidemiology" and "Nontyphoidal Salmonella bacteremia".)
Acute diarrhea is also often approached syndromically, without knowledge of the causative pathogen. This approach differs somewhat by age and setting and is discussed elsewhere. (See "Approach to the adult with acute diarrhea in resource-rich settings" and "Approach to the adult with acute diarrhea in resource-limited countries" and "Diagnostic approach to diarrhea in children in resource-rich countries", section on 'Acute diarrhea (duration <5 days)'.)
EPIDEMIOLOGY — Nontyphoidal salmonellae are a major cause of diarrhea worldwide. In the United States, nontyphoidal salmonellosis is one of the leading causes of foodborne disease [1]. Salmonella Enteritidis, S. Newport, and S. Typhimurium are among the serotypes most frequently isolated. Salmonella is most commonly associated with ingestion of poultry, eggs, and milk products. However, nontyphoidal salmonellae have also been associated with fresh produce, meats, and other foodstuff, as well as contact with pets, including reptiles, and other animals [2]. This is discussed in detail elsewhere. (See "Nontyphoidal Salmonella: Microbiology and epidemiology", section on 'Epidemiology'.)
CLINICAL MANIFESTATIONS
Incubation period — Symptoms of Salmonella gastroenteritis typically occur within 8 to 72 hours following exposure, usually ingestion of contaminated food or water. However, longer incubation periods have been reported in some outbreaks, potentially as a result of exposure to a lower bacterial dose [3,4]
General features — Gastroenteritis due to salmonellae is clinically indistinguishable from gastroenteritis caused by many other pathogens. Furthermore, enteric infection with nontyphoidal salmonellae may be clinically mild or even asymptomatic, which can complicate clinical decisions about treatment interventions. (See 'Asymptomatic carriage' below.)
The cardinal features include diarrhea, nausea, vomiting, fever, and abdominal cramping. A higher ingested dose of bacteria correlates with severity of diarrhea, the duration of illness, and weight loss [5]. Although there have been descriptions of clinical characteristics associated with salmonellosis (eg, "pea soup" diarrhea), there are no clinical characteristics that reliably distinguish Salmonella infection from other forms of gastroenteritis. The diarrhea is typically not grossly bloody, although bloody stools can be seen, particularly among children [6,7].
Other constitutional symptoms (fatigue, malaise, chills), weight loss, and headaches are also commonly described.
Course — Nontyphoidal Salmonella gastroenteritis is usually self-limited. Fever generally resolves within 48 to 72 hours, and diarrhea within 4 to 10 days [7,8].
Mortality rates of 0.5 to 1 percent have been reported in outbreaks of S. enteritidis, but these are most likely overestimates since milder cases tend to be unrecognized [9,10].
Complications/invasive disease — Fewer than 5 percent of individuals with documented Salmonella gastroenteritis develop bacteremia [7,11]. Bacteremia can lead to a variety of extraintestinal manifestations such as endocarditis, mycotic aneurysm, visceral abscesses, and osteomyelitis [12]. Two species, Salmonella choleraesuis [13,14] and Salmonella heidelberg [15,16], appear to be more invasive than others. In addition, antibiotic resistant strains of S. typhimurium are associated with a two- to threefold increase in the risk of bacteremia [11,17]. (See "Nontyphoidal Salmonella bacteremia".)
DIAGNOSIS AND EVALUATION — Nontyphoidal Salmonella gastroenteritis is generally suspected as part of the differential diagnosis of acute diarrhea, particularly when accompanied by abdominal cramping and fever or in the setting of a community outbreak. The definitive diagnosis of Salmonella gastroenteritis requires isolation of the pathogen in stool cultures from such patients, although stool cultures are not always warranted. Indications for stool cultures in a patient presenting with acute diarrhea include severe illness, immunocompromising conditions, and comorbidities that increase the risk for complications; these indications are discussed elsewhere. Patients at the extremes of age are more likely to have complications in the setting of Salmonella gastroenteritis. Blood cultures should generally be obtained in such individuals, particularly if they remain ill or febrile by the time stool culture results return. (See "Nontyphoidal Salmonella: Microbiology and epidemiology", section on 'Risk for severe disease'.)
Laboratory isolation of salmonellae from stool usually requires a minimum of 48 hours; 72 hours is needed if overnight enrichment broth incubation is used in addition to primary plating of stool samples. Salmonellae are gram-negative, facultatively anaerobic Enterobacteriaceae, which are differentiated from the normal gram-negative flora of the intestinal tract, in part, by the color of the colonies on indicator plates. The sensitivity and specificity of single or multiple stool cultures for diagnosis of salmonellosis are unknown. Enrichment broths (tetrathionate or selenite) are used to facilitate identification of Salmonella when low numbers of organisms are present. Overnight incubation in these broths inhibits the growth of Escherichia coli but not Salmonella. Highly sensitive multiplex nucleic acid amplification tests are commercially available for detection of Salmonella and other enteric pathogens in stool samples, though their clinical utility and cost remain uncertain [18,19]. (See "Nontyphoidal Salmonella: Microbiology and epidemiology", section on 'Microbiology'.)
DIFFERENTIAL DIAGNOSIS — Most cases of acute diarrhea are due to infections. The other major causes of acute infectious diarrhea include viruses (eg, norovirus, rotavirus, adenoviruses, astrovirus), other bacteria (eg, Campylobacter, Shigella, Shiga-toxin producing E. coli, Vibrio, Clostridioides difficile), and protozoa (eg, cryptosporidium, giardia, cyclospora, entamoeba). It is difficult to distinguish infections caused by the different pathogens on the basis of clinical features alone, but identifying a pathogen is not always warranted for clinical management. The differential diagnosis and approach to acute diarrhea are discussed in detail elsewhere. (See "Approach to the adult with acute diarrhea in resource-rich settings" and "Approach to the adult with acute diarrhea in resource-limited countries" and "Diagnostic approach to diarrhea in children in resource-rich countries", section on 'Acute diarrhea (duration <5 days)' and "Causes of acute infectious diarrhea and other foodborne illnesses in resource-rich settings", section on 'Overview of causes'.)
MANAGEMENT — The cornerstone of therapy of symptomatic individuals with Salmonella gastroenteritis is replacement of fluids and electrolytes. As noted above, the illness is usually self-limited; in addition, the vast majority of Salmonella infections are undiagnosed and are not associated with complications. Antimicrobial therapy (typically fluoroquinolones) may be warranted for those with severe disease or risk factors for invasive disease.
Supportive management — The most critical therapy in diarrheal illness is hydration, preferably by the oral route with solutions that contain water, salt, and sugar. This is discussed in detail elsewhere. (See "Approach to the adult with acute diarrhea in resource-rich settings", section on 'Fluid repletion' and "Approach to the adult with acute diarrhea in resource-limited countries", section on 'Rehydration' and "Treatment of hypovolemia (dehydration) in children".)
Antimicrobial therapy — Decisions about antimicrobial therapy are generally made empirically at the time that patients present. The following sections discuss the approach to antimicrobial therapy for patients who have documented Salmonella gastrointestinal infection. The issue of empiric antimicrobial therapy for infectious diarrhea in general is discussed elsewhere. (See "Approach to the adult with acute diarrhea in resource-rich settings" and "Approach to the adult with acute diarrhea in resource-limited countries" and "Approach to the child with acute diarrhea in resource-limited countries".)
Treatment of extraintestinal Salmonella infections is also discussed in detail elsewhere. (See "Nontyphoidal Salmonella bacteremia", section on 'Treatment'.)
Indications — We generally do not recommend antibiotic treatment for immunocompetent individuals between 12 months and 50 years of age who have documented Salmonella gastroenteritis with mild to moderate symptoms, as the illness is typically self-limited. A meta-analysis of 12 trials that included 767 otherwise healthy individuals with nontyphoidal Salmonella gastroenteritis found no significant benefit from antimicrobial therapy on the duration of illness, diarrhea, or fever [20]. The main risks of treatment include the adverse effects of the antimicrobial agent (including overall antimicrobial resistance pressure) and the potential for extending asymptomatic Salmonella carriage. (See 'Risk from prior antimicrobial therapy' below.)
However, there are certain clinical settings in which therapy for Salmonella gastrointestinal infection is warranted, specifically for treatment of severe disease and for pre-emptive treatment in immunocompromised patients and those at the extremes of age, who are at higher risk of complications (eg, bacteremia, focal infection, or persisting symptoms). In these patients, the potential for improvement of severe illness and prevention of complications seems to outweigh the risks of antibiotic treatment, although this has not been definitively demonstrated in large, randomized placebo-controlled trials.
●Severe illness — Antimicrobial treatment is appropriate in severely ill immunocompetent individuals, although the decision to treat should be individualized. Severe illness is characterized by:
•Severe diarrhea (more than 9 or 10 stools per day)
•High or persistent fever
•A need for hospitalization
The presence of bloody diarrhea does not necessarily indicate the need for antimicrobial treatment. Many patients with salmonellosis have occult blood detectable in stool samples, while overtly bloody stools are more likely to be due to Shigella or enterohemorrhagic E. coli, the latter for which antibiotic treatment has been associated with Shiga-toxin mediated hemolytic uremic syndrome. (See "Shiga toxin-producing Escherichia coli: Clinical manifestations, diagnosis, and treatment", section on 'Antibiotics'.)
Use of antibiotics in patients with severe illness is supported by trials suggesting that empiric antimicrobial treatment of patients with severe community-acquired diarrhea improves symptoms and speeds clinical recovery by one to two days [21-24]. Studies included in the meta-analysis discussed above that showed minimal clinical benefit of antimicrobial treatment of nontyphoidal Salmonella gastroenteritis generally excluded patients with severe disease [20].
●High risk of invasive disease — Pre-emptive therapy, regardless of the severity of disease, is warranted in certain patients at high risk for complications of Salmonella intestinal infection, such as bacteremia and metastatic foci of infection, in an attempt to prevent them. Such patients include:
•Young infants <12 months
•Adults over 50
•Human immunodeficiency virus (HIV)-infected patients
•Other immunocompromised patients (eg, organ transplant recipients; those receiving corticosteroids or other immunosuppressive agents; those with cancer or lymphoproliferative disease with current or recent chemotherapy; those with sickle cell disease, hemoglobinopathies, disorders of the reticuloendothelial system, including cirrhosis)
•Other individuals with cardiac, valvular, endovascular abnormalities or substantial joint disease
Older adults and the very young are at increased risk for complications. Neonates with gastroenteritis, particularly those born prematurely and/or to mothers with gastroenteritis, are at risk and may not appear toxic or acutely ill [16,25,26]. Salmonella meningitis is a feared complication that occurs primarily in infants and has a high case fatality rate and significant rate of neurologic complications [27]. In most cases, infants less than three months of age should receive antimicrobial therapy for symptomatic salmonellosis [28,29]; in addition, some experts treat all children younger than one to two years old unless the child is afebrile and clinically improving at the time the culture results become available [25].
Adults over 50, particularly those with known atherosclerotic disease, are at higher risk of endovascular infection and aortitis if bacteremia develops. Approximately 10 percent of adults over 50 years old who are diagnosed with nontyphoidal Salmonella bacteremia will be found to have infective arteritis [30,31]. Those with endovascular or osseous prostheses may also reasonably be considered to have similar risk of metastatic infection, and should similarly be treated even if not severely ill with gastroenteritis.
Immunodeficiency is a major risk factor for Salmonella bacteremia and extraintestinal infection [32]. It is impossible to know precisely how many patients with immunocompromising conditions who get mild to moderate gastrointestinal salmonellosis go on to develop bacteremia and complications. However, it is likely to be a significant percentage and a cause for worry. As an example, in two studies (one from Malawi and the other from Taiwan), 31 and 43 percent of HIV-infected antiretroviral-naïve adults developed recurrent Salmonella bacteremia [33,34]. A subsequent study demonstrated that successful initiation of antiretroviral treatment (ART) following Salmonella infection, with a decrease in the plasma HIV viral level by ≥2 log10 after four weeks, is associated with a reduced risk of recurrence, even without suppressive antibiotics, compared with those who had a poor virologic response after ART initiation [35].
The association between these host factors and more severe disease are discussed in detail elsewhere. (See "Nontyphoidal Salmonella: Microbiology and epidemiology", section on 'Risk for severe disease' and "Nontyphoidal Salmonella bacteremia", section on 'Host risk factors'.)
Since antimicrobial therapy appears to suppress excretion of large numbers of organisms acutely, it thus may be useful in decreasing transmission in certain situations. Drug treatment may occasionally be useful in limiting epidemics in closed settings in which full compliance with infection control measures may be difficult, such as pediatric wards [36] or long-term care facilities [37].
Antibiotic selection — Fluoroquinolones (eg, ciprofloxacin 500 mg orally twice daily or levofloxacin 500 mg orally once daily) are generally the most appropriate agents for adults and adolescents without contraindications to these medications because of their activity against most common gram-negative enteric pathogens, their high tissue and intracellular concentrations, and their favorable side effect profile. Fluoroquinolones are frequently avoided in children because of cartilage abnormalities observed in exposed developing animals, although data suggest that fluoroquinolones may be used safely in children over short courses [38]. Treatment of serious Salmonella infections is a reasonable indication for use of fluoroquinolones in children, especially if other agents are not readily available.
Other appropriate antibiotic choices include trimethoprim-sulfamethoxazole (160 mg/800 mg orally twice daily), cefixime (400 mg orally once or twice daily), or azithromycin (1 gram, followed by 500 mg daily for five to seven days). For patients with severe disease who cannot tolerate oral therapy, an intravenous fluoroquinolone or a third generation cephalosporin (eg, ceftriaxone 1 to 2 g intravenously once daily or cefotaxime 2 g intravenously every eight hours) can be given.
Given the increasing prevalence of antimicrobial resistance, local antibiotic resistance patterns must be taken into account when choosing empiric therapy. This problem also supports performing stool culture to inform future therapy if the patient does not improve clinically or to confirm the expected activity of an empirically chosen regimen. (See "Nontyphoidal Salmonella: Microbiology and epidemiology", section on 'Antimicrobial resistance'.)
Duration
●Immunocompetent patients − For immunocompetent individuals with severe gastrointestinal, non-bacteremic Salmonella infection that warrants antibiotic therapy, three to seven days of treatment is generally appropriate. This has been the range of durations evaluated in most studies of empiric treatment of severe community-acquired diarrhea [21-24].
The duration of therapy for immunocompetent patients who are treated because of age or underlying vascular or joint disease has not been studied. Most experts would recommend 3 to 14 days of treatment depending upon the specific clinical situation, suspicion of bacteremia, laboratory findings, and microbiologic data.
Overall, it is prudent to limit the exposure to antibiotics in immunocompetent hosts because of the potential for antibiotics to paradoxically prolong carriage and cause adverse drug reactions, and because of concerns about antibiotic resistance in general. (See 'Short-term carriage following infection' below.)
●Immunosuppressed patients − We treat immunosuppressed patients with salmonellosis for a longer duration (at least 14 days; weeks to months in some cases) to prevent persistent or relapsing infection, because salmonellae persist in the reticuloendothelial system, and these patients have impaired immune clearance mechanisms (especially those with advanced HIV or organ transplants). For HIV-infected patients with CD4 cell counts <200 cells/microL, two to six weeks of antibiotics is generally recommended for Salmonella gastroenteritis [39]. Immunosuppressed patients should be evaluated carefully for bacteremia or extraintestinal infection, and decisions on the precise duration of treatment should be individualized. Consultation with an expert in infectious diseases is recommended.
A retrospective study of cancer patients (primarily hematologic malignancies) with nontyphoidal salmonellosis showed that many presented with bacteremia. Relapses were more common in patients treated with less than or equal to 10 days, reinforcing the need for longer therapy in this group [40].
Follow-up — In general, we do not check convalescent cultures to evaluate for clearance of Salmonella. Continued short-term shedding of Salmonella following infection is very common, and in the patient who has clinically recovered, a "test of cure" can prompt unnecessary interventions. (See 'Short-term carriage following infection' below.)
ASYMPTOMATIC CARRIAGE
Short-term carriage following infection — Asymptomatic convalescent excretion of Salmonella is common after either symptomatic or asymptomatic nontyphoidal Salmonella infection [41]. Routine follow-up cultures are not recommended after uncomplicated Salmonella gastroenteritis in immunocompetent patients, particularly if symptoms have resolved. Antibiotic treatment is also not indicated for patients incidentally found to have continued Salmonella isolation from the stools following an episode of gastroenteritis. Immunocompromised patients may warrant special consideration; infectious disease consultation is advised.
Carriage following infection has generally been assessed through stool cultures and is relatively common [41]:
●The median duration of excretion following infection is approximately five weeks.
●Age younger than five years is associated with a longer duration of excretion, with a median of approximately seven weeks. Among this age group, 2.6 percent excrete salmonellae for more than one year, compared with less than 1 percent among all age groups. (See 'Chronic carriage' below.)
●The duration of excretion may be longer after symptomatic than asymptomatic infection.
●S. typhimurium is more rapidly cleared than other serotypes.
●Intermittent shedding is common, so a single negative culture is not that reassuring.
Antibiotic therapy of symptomatic diarrheal illness does not prevent or shorten the duration of carriage, and in some studies, is associated with a longer duration of excretion. This is discussed in detail below. (See 'Risk from prior antimicrobial therapy' below.)
Furthermore, short-course antibiotic treatment of asymptomatic carriage is not effective in eradicating it and may promote resistance. In a Thai study of food handlers who had asymptomatic Salmonella carriage and were randomly assigned to five days of norfloxacin, azithromycin, or placebo, the study drugs were no better than placebo in eradicating shedding [42]. Also, in this endemic setting for nontyphoidal salmonellosis, antibiotic use was associated with selection of drug-resistant Salmonella. Nevertheless, for certain individuals with chronic carriage (more than one year), a prolonged course of antibiotic therapy may be warranted to attempt eradication. (See 'Chronic carriage' below.)
Risk from prior antimicrobial therapy — Brief early courses of antibiotics for gastroenteritis are not effective in shortening the duration of subsequent carriage of nontyphoidal salmonellae. Non-fluoroquinolone antibiotics have been associated with an increased risk of subsequent Salmonella carriage [43,44]. The risk with fluoroquinolone antibiotics is uncertain because of conflicting data, due in part to differences in culture techniques, culture intervals, infecting strains, and duration of follow-up.
Studies performed in the pre-quinolone era demonstrated that antimicrobial therapy of Salmonella gastroenteritis prolonged the duration of Salmonella excretion. As an example, in a 1980 study of children and infants treated with five days of ampicillin, amoxicillin, or placebo for uncomplicated Salmonella gastroenteritis, 53 percent of those who received antibiotics had bacteriologic relapse compared with none who received placebo [43]. Of those who relapsed, 38 percent had recurrent diarrhea. This paradoxical finding has been thought to be due to the deleterious effect of antibiotics on normal intestinal flora, which protects against colonization with enteric pathogens. Prolongation of carriage is not related to the emergence of organisms resistant to the antimicrobial agent used, which is a relatively rare event. (See "Pathogenesis of Salmonella gastroenteritis".)
Fluoroquinolones were anticipated to be more effective in eliminating convalescent carriage. This hypothesis was evaluated in two small randomized placebo-controlled treatment studies of outbreaks of Salmonella gastroenteritis using norfloxacin (400 mg twice daily for seven days) [45] or ciprofloxacin (750 mg twice daily for 14 days) [46]. Neither of the treatment regimens in these studies decreased or prolonged the duration of carriage. In contrast, a deleterious effect of norfloxacin was noted in the patients with salmonellosis treated in a placebo-controlled trial of empiric treatment for acute diarrhea [21]. In this study, receipt of norfloxacin was associated with a lower incidence of clearance of Salmonella stool culture at 12 to 17 days (18 versus 49 percent with placebo). Norfloxacin was also associated with a longer time to negative cultures (median 50 versus 23 days).
Chronic carriage — Chronic carriage of nontyphoidal Salmonella is defined as the shedding of a Salmonella species for more than one year, as documented by an initial positive culture of a stool sample obtained at least one month after resolution of the acute illness and repeat positive cultures [47]. Chronic carriage appears to occur rarely (0.2 to 0.6 percent in one study [48]) in otherwise healthy subjects but may occur somewhat more frequently in young children, older individuals, women, and those with biliary tract abnormalities, especially gallstones. Chronic carriage is often identified incidentally, as part of public health follow-up, or when episodic or recurrent gastrointestinal symptoms prompt additional testing.
If chronic carriage is documented, attempted eradication may rarely be needed for employment or other social reasons like daycare attendance or the presence of a severely immunosuppressed family member. Eradication may also be warranted for immunosuppressed patients, particularly those with advanced HIV infection, who are at higher risk of complications from Salmonella infection. It is possible that chronic carriage of nontyphoidal Salmonella is associated with gall bladder and other cancers, as seen with chronic S. typhi carriage [49]. (See "Gallbladder cancer: Epidemiology, risk factors, clinical features, and diagnosis", section on 'Salmonella'.)
In contrast to short-term antibiotics, which can prolong the duration of Salmonella carriage post-infection when given for symptomatic gastroenteritis and has not been demonstrated to eradicate carriage when given to asymptomatic individuals, long-term antimicrobial therapy may be of some utility in patients who have prolonged or chronic carriage. The optimal approach to chronic carriage of nontyphoidal Salmonella has not been well studied [41]. Drawing upon the experience with treating carriage of S. typhi, four to six weeks of antimicrobial therapy is a reasonable approach, although many patients may have side effects related to treatment. When attempting eradication of carriage, we use a fluoroquinolone (eg, ciprofloxacin 500 mg orally twice daily or levofloxacin 500 mg orally once daily) for four weeks. Alternative regimens that have successfully eradicated S. typhi in some patients include trimethoprim-sulfamethoxazole (160 mg/800 mg orally twice daily) for three months or ampicillin or amoxicillin (3 to 5 g orally in four divided doses) for six weeks (depending upon susceptibilities of the isolate). A combination of cholecystectomy plus antibiotic therapy is probably most effective but does not guarantee carriage will be eradicated. (See "Enteric (typhoid and paratyphoid) fever: Treatment and prevention", section on 'Chronic carriage'.)
Some experts have suggested performing follow-up cultures six months after completing therapy in order to confirm eradication [47]. In addition, suppressive prophylactic therapy may be warranted in HIV-infected individuals, particularly, in those with a bacteremic primary illness, low CD4 cell counts, or poor response to antiretroviral therapy [35], in order to prevent relapse [50].
CONSIDERATIONS FOR SPECIFIC POPULATIONS
Pregnant women and their neonates — Pregnant women acquire nontyphoidal Salmonella infection at rates similar to the general population [51,52]. Pregnancy does not necessarily increase severity of illness, although there are case reports of pregnant women with severe nontyphoidal Salmonella infection, and fetal loss in the setting of disseminated infection is possible in any trimester [53-55]. Transplacental transmission is possible and can precipitate preterm delivery and neonatal complications [56]. Pregnant woman with fever and gastroenteritis symptoms should be evaluated for salmonellosis as well as other enteric bacterial infections (including Campylobacter and Listeria).
As with other immunocompetent adults or adolescents, routine treatment of salmonellosis in pregnancy is not necessary, particularly in the setting of mild illness early in pregnancy; antibiotics may not speed resolution or mitigate symptoms, and may prolong Salmonella carriage. (See 'Risk from prior antimicrobial therapy' above.)
Antibiotic therapy for treatment of salmonellosis in pregnancy is appropriate for febrile patients with severe disease, especially in the setting of bacteremia or infection near term. Women with peripartum infection may shed organisms during childbirth with high risk for neonatal transmission of infection [57]. If severe illness occurred early in pregnancy, there is no role for additional treatment at the time of delivery.
Prophylaxis of neonates may be appropriate in some situations to prevent complications of systemic neonatal salmonellosis, including meningitis [58,59]. In addition, outbreaks of salmonellosis in neonatal ICUs and maternity wards have been described [60,61].
Infectious disease consultation is advisable to assist with management and follow-up evaluation; these must be individualized depending on clinical circumstances including the patient, the organism, and presence of antibiotic resistance.
Food handlers and health care workers — Individuals who work in food service are potential sources of Salmonella outbreaks, and health care personnel could potentially transmit to patients with substantial comorbidity. It is reasonable and customary for such individuals to remain home from work while gastroenteritis symptoms persist [62], since organism excretion is more common and at higher levels during active disease. However, there is no evidence that such individuals are a major source of outbreaks when asymptomatic, and there is no evidence that screening for asymptomatic carriage in such individuals is effective in reducing transmission. Hand hygiene and general infection control practices remain the most important aspects of preventing spread of Salmonella.
Large numbers of asymptomatic transient Salmonella excreters are undoubtedly employed in the health care and food industries worldwide for the following reasons:
●The initial episode of Salmonella gastroenteritis may be clinically mild and remain undiagnosed
●The median duration of Salmonella excretion after gastroenteritis is five weeks and excretion is frequently episodic (see 'Short-term carriage following infection' above)
Nevertheless, in one study, only 2 percent of 566 outbreaks of salmonellosis in the United Kingdom were traced to specific infected food handlers [63]. Furthermore, transmission from asymptomatic food handlers has only rarely been documented [64,65]. One of these outbreaks was in Amman, Jordan and occurred despite routine surveillance of kitchen employees for Salmonella carriage [65]. Nosocomial fecal-oral transmission is often related to poor handwashing practices [66,67]. The importance of handwashing was illustrated in a foodborne outbreak of salmonellosis among nurses; there was no transmission to patients, presumably because of adherence to proper handwashing procedures [68].
In the United States, some states require one or more negative stool cultures (more than 48 hours after discontinuation of antibiotics, if given) before such employees can return to work. A similar approach may be locally mandated, or instituted during outbreaks in daycare centers, but scrupulous attention to proper infection control procedures are most important. While reassuring, a single negative stool culture does not ensure that the individual is no longer shedding [41]. Obtaining multiple negative stool cultures from employees may be warranted occasionally in individuals whose work requires direct handling of food that is to be consumed without further cooking, or direct contact with infants or immunosuppressed patients. However, it does not seem reasonable to routinely implement this approach for employees with lower risk occupations. As national policy for these settings is not mandated, judgments based upon individual employees and local health administration standards are appropriate.
SOCIETY GUIDELINE LINKS — Links to society and government-sponsored guidelines from selected countries and regions around the world are provided separately. (See "Society guideline links: Acute diarrhea in adults" and "Society guideline links: Acute diarrhea in children".)
INFORMATION FOR PATIENTS — UpToDate offers two types of patient education materials, "The Basics" and "Beyond the Basics." The Basics patient education pieces are written in plain language, at the 5th to 6th grade reading level, and they answer the four or five key questions a patient might have about a given condition. These articles are best for patients who want a general overview and who prefer short, easy-to-read materials. Beyond the Basics patient education pieces are longer, more sophisticated, and more detailed. These articles are written at the 10th to 12th grade reading level and are best for patients who want in-depth information and are comfortable with some medical jargon.
Here are the patient education articles that are relevant to this topic. We encourage you to print or e-mail these topics to your patients. (You can also locate patient education articles on a variety of subjects by searching on "patient info" and the keyword(s) of interest.)
●Basics topic (see "Patient education: Salmonella infection (The Basics)")
SUMMARY AND RECOMMENDATIONS
●Epidemiology − Enteric fever is caused by Salmonella typhi and Salmonella paratyphi. Other Salmonella serotypes are collectively known as nontyphoidal salmonellae and are frequently isolated from the stool of patients with gastroenteritis. Salmonella infection is most commonly associated with ingestion of poultry, eggs, and milk products, but many other food products and animal contacts are also sources of infection. These are discussed in detail elsewhere. (See "Nontyphoidal Salmonella: Microbiology and epidemiology", section on 'Epidemiology'.)
●Clinical manifestations − Symptoms of Salmonella gastroenteritis typically occur within 8 to 72 hours following exposure. The cardinal features include diarrhea, nausea, vomiting, fever, and abdominal cramping, and are usually self-limited. Fever generally resolves within 48 to 72 hours, and diarrhea within 4 to 10 days. (See 'Clinical manifestations' above.)
●Diagnosis and evaluation − Nontyphoidal Salmonella gastroenteritis is generally suspected as part of the differential diagnosis of acute diarrhea, particularly when accompanied by abdominal cramping and fever or in the setting of a community outbreak. Gastroenteritis due to salmonellae is clinically indistinguishable from gastroenteritis caused by other pathogens, and definitive diagnosis requires isolation of Salmonella on stool cultures. However, identifying a pathogen is not always warranted for clinical management of acute diarrhea. Indications for stool cultures in a patient presenting with acute diarrhea include severe illness, immunocompromising conditions, and comorbidities that increase the risk for complications. (See 'Diagnosis and evaluation' above and 'Differential diagnosis' above and "Causes of acute infectious diarrhea and other foodborne illnesses in resource-rich settings".)
●Management
•Supportive care
-The cornerstone of therapy of symptomatic Salmonella gastroenteritis is replacement of fluids and electrolytes. The role of antibiotics depends upon the clinical setting. (See 'Supportive management' above.)
-For immunocompetent patients 12 months to 50 years old with mild to moderately illness, we suggest not routinely treating Salmonella gastroenteritis with antibiotics (Grade 2B). In such patients, antimicrobial therapy does not shorten the duration of illness and can increase the risk of extended asymptomatic carriage of Salmonella. (See 'Indications' above.)
•Role for antimicrobial therapy − For patients at risk for severe infection, the potential for antibiotics to improve disease or prevent complications appears to outweigh the risks of antibiotic use. These patients include:
-Individuals with severe illness (high or persistent fever, very frequent bowel movements, need for hospitalization)
-Infants <12 months
-Adults >50 years
-HIV-infected patients
-Immunocompromised patients
-Individuals with cardiac, valvular, endovascular abnormalities or substantial joint disease
For these individuals, we suggest treating Salmonella gastroenteritis with antibiotics (Grade 2C). (See 'Indications' above.)
•Antibiotic selection − Fluoroquinolones (eg, ciprofloxacin 500 mg orally twice daily or levofloxacin 500 mg orally once daily) are generally the most appropriate agents for adults and adolescents who warrant treatment for Salmonella gastrointestinal infection. Serious Salmonella infection is also a reasonable indication for use of fluoroquinolones in children, especially if other agents are not readily available. Other appropriate antibiotic choices include trimethoprim-sulfamethoxazole, cefixime, and azithromycin. (See 'Antibiotic selection' above.)
•Duration − For immunocompetent individuals with severe gastrointestinal, non-bacteremic Salmonella infection that warrants antibiotic therapy, three to seven days of treatment is generally appropriate. For immunocompetent patients who are given antibiotics because of age or underlying vascular or joint disease, 3 to 14 days of treatment is reasonable depending upon the specific clinical situation, suspicion of bacteremia, laboratory findings, and microbiological data. It is appropriate to treat immunocompromised patients for a longer duration (eg, 14 days or even for weeks to months) in an effort to prevent persistent or relapsing infection. (See 'Duration' above.)
●Asymptomatic carriage
•Short-term carriage − Asymptomatic convalescent excretion of Salmonella is extremely common after either symptomatic or asymptomatic nontyphoidal Salmonella infection, and routine follow-up cultures are not warranted after uncomplicated Salmonella gastroenteritis in immunocompetent patients, particularly if symptoms have resolved. Immunocompromised patients may warrant special consideration. (See 'Short-term carriage following infection' above.)
•Chronic carriage − In contrast, chronic carriage of nontyphoidal Salmonella (shedding of a Salmonella species for more than one year) is rare in otherwise healthy individuals but may occur in older individuals and those with biliary tract abnormalities, especially gallstones. The optimal approach to chronic carriage of nontyphoidal Salmonella has not been well studied; based on evidence from patients with chronic S. typhi carriage, four to six weeks of antimicrobial therapy is a reasonable approach. Cholecystectomy may also be warranted. (See 'Chronic carriage' above.)
●Reducing transmission risk − It is customary for food handlers and health care workers with Salmonella gastroenteritis to remain home from work while symptoms persist because of the risk of transmission. However, there is no evidence that such individuals are a major source of outbreaks or infection when asymptomatic. Hand hygiene and general infection control practices remain the most important aspects of preventing spread of Salmonella. Practitioners should be aware of the need to comply with local public health requirements, which vary. (See 'Food handlers and health care workers' above.)
