Salmonellosis

Overview 
Theory 
Diagnosis 
Management 
Follow up 
Resources 

Salmonella gastroenteritis is typically self-limiting, and antibiotics should not be used in most cases. For patients meeting specific criteria for antibiotic use, the goal of therapy is to resolve the infection and lower the rate of more severe disease or extraintestinal complications.

Supportive treatment

Fluid replacement

All patients with gastroenteritis should be assessed for volume depletion and electrolyte imbalances.[82]

Most individuals with acute diarrhoea or gastroenteritis are able to maintain fluid and salt balances through the consumption of water, juices, sports drinks, soups, and saltine crackers.[68]

Reduced osmolarity oral rehydration solution (ORS) is recommended for mild to moderate dehydration:[66]

in infants, children, and adults with acute diarrhoea

associated with vomiting or severe diarrhoea.

Infants, children, and adults with mild to moderate dehydration should receive ORS until clinical dehydration is corrected.[66]

Once the patient is rehydrated, maintenance fluids should be administered. Replace ongoing losses in stools from infants, children, and adults with ORS, until diarrhoea and vomiting are resolved.[66]

Nasogastric administration of ORS may be considered in infants, children, and adults with moderate dehydration, who cannot tolerate oral intake, or in children with normal mental status who are too weak or who refuse to drink adequately.[66]

Severe dehydration

Intravenous fluids, such as lactated Ringer’s and normal saline solution, should be administered when there is severe dehydration, shock, or altered mental status and failure of ORS therapy or ileus.[66] The use of balanced crystalloid solutions may be associated with slightly shorter duration of hospitalisation in children, compared with normal saline.[83] [ ] Intravenous rehydration should be continued until pulse, perfusion, and mental status normalise, and the patient awakens, has no risk factors for aspiration, and has no evidence of ileus.

Anti-diarrhoeal/anti-emetic treatment

Treatment with an anti-diarrhoeal and/or an anti-emetic is not a substitute for fluid and electrolyte therapy.[66] It can be considered once the patient is adequately hydrated.

Loperamide, an anti-diarrhoeal agent, may be given to immunocompetent adults with acute watery diarrhoea, but should be avoided in suspected or proven cases where toxic megacolon may result in inflammatory diarrhoea, or diarrhoea with fever. Loperamide should not be given to children <18 years of age with acute diarrhoea.[66]

Bismuth subsalicylate, another anti-diarrhoeal, can be given to adults to control rates of passage of stool, and may help patients function better during bouts of mild to moderate illness.[68]

Ondansetron, an anti-emetic, may be given to facilitate tolerance of oral rehydration in children >4 years of age, and in adolescents with acute gastroenteritis associated with vomiting.[66] [ ]

Probiotics

Probiotics may be offered to reduce the symptom severity and duration in immunocompetent adults and children with infectious or antimicrobial-associated diarrhoea.[66]

Zinc

Oral zinc supplementation reduces the duration of diarrhoea in children 6 months to 5 years of age who reside in countries with a high prevalence of zinc deficiency, or who have signs of malnutrition.[66]

Medical treatments

As most cases of gastroenteritis are self-limited in nature, antibiotics are not recommended as the initial treatment.[66][68] However, although antibiotics do not shorten the duration of symptoms in uncomplicated and self-limited cases of gastroenteritis, they may be beneficial in severe or complicated infections and in patients at increased risk of complications, including immunocompromised hosts.[84][85][86][87]

Empiric antibiotic treatment is not recommended for patients who are immunocompetent who have bloody diarrhoea while waiting for the results of investigations.[66]

The use of antibiotics does not significantly shorten the length of illness or decrease symptoms in typical cases.[84][88][89][90][91] Furthermore, antibiotics may cause adverse effects, prolong the carriage of Salmonella, and increase the risk of relapse.[84] Treatment of an undifferentiated diarrhoeal illness (e.g., Shiga toxin-producing Escherichia coli) with an antibiotic may have adverse consequences, such as a potentially increased risk of haemolytic uraemic syndrome.[92]

Patients at risk of developing severe disease

For patients with severe illness, or who are at high risk of developing more severe disease i.e., bacteraemia, or other forms of extraintestinal salmonellosis, a short course of oral antibiotics should be considered. These patient groups include:[44][45][66][93][94][95]

Infants <3 months of age with suspicion of a bacterial aetiology
adults over 50 years, to reduce the risk of seeding pre-existing atherosclerotic lesions with bacteraemia
HIV-infected patients
people who have recently travelled internationally with body temperatures ≥38.5°C (101.3°F) and/or signs of sepsis
patients with vascular abnormalities, such as prosthetic valves or grafts
patients with prosthetic joints
immunocompromised people with severe illness and bloody diarrhoea.

Antibiotics recommended to treat adults include a fluoroquinolone (e.g., ciprofloxacin) or azithromycin, depending on the local susceptibility patterns and travel history.[66][68]

Resistance to fluoroquinolones has been described in some locations; therefore patients without an appropriate clinical response to a fluoroquinolone should be considered for alternative antibiotic therapy based on susceptibility results.[96][97] In 2012, the Clinical Laboratory Standards Institute (CLSI) adjusted the fluoroquinolone breakpoints for Salmonella in recognition of reports of suboptimal treatment responses in infections caused by strains with modest reductions in in vitro susceptibility.[98] A UK study suggested that foreign travel is associated with having a fluoroquinolone-resistant strain.[99]

Fluoroquinolones are associated with serious, disabling, and potentially irreversible adverse effects including tendonitis, tendon rupture, arthralgia, neuropathies, and other musculoskeletal or nervous system effects.[100][101] The US Food and Drug Administration has also issued warnings about the increased risk of aortic dissection, significant hypoglycaemia, and mental health adverse effects in patients taking fluoroquinolones.[102][103]

Alternative antibiotic therapy

A third-generation cephalosporin or azithromycin is recommended specifically for infants <3 months of age, depending on local susceptibility patterns and travel history.[66]

Treatment of children is complicated, given both increasing resistance among Salmonella isolates and potential toxicity of fluoroquinolone antibiotics in paediatric patients.[97][104][105][106][107]

A study of ciprofloxacin for the treatment of typhoid fever suggested that it may be used safely for Salmonella infections.[108] Ciprofloxacin is generally not recommended in the paediatric population due to the potential risk of arthropathy, but there are reports of successful and safe use in this patient population for certain indications.[109]

Studies (both in vitro and in vivo) have suggested that carbapenems and tigecycline may be active against non-typhoidal strains, but further research is needed before these are recommended in clinical practice.[110][111] Clinical experience with tigecycline in Salmonella infections is very limited.[112] Clinical experience with carbapenems is also limited, and failures with meropenem have been reported.[113][114] Ertapenem may be preferred due to its ability to kill intracellular Salmonella.[111]

Treatment failure

Patients not responding to antibiotic therapy should be assessed for the possibility of a drug-resistant Salmonella strain.

Resistance has been associated with a greater risk of complicated disease and mortality.[60] Antimicrobial susceptibility testing should therefore be performed on every clinical isolate. Antimicrobial therapy should be altered during clinical failures and be based on susceptibility results.[66]

Chronic carrier state

A chronic carrier state is defined as positive stool or urine culture for Salmonella at 12 months or more following the acute illness.[32]

Chronic carriage of non-typhoidal Salmonella occurs in 0.5% of cases (compared with 3% of those with S Typhi).[33] Certain groups are at higher risk for chronic carriage, including infants, women, patients with gallstones or kidney stones, and patients co-infected with Schistosoma haematobium.

Prolonged carriage may be treated with long-term antibiotic therapy, and surgery should be considered in the case of concurrent gallstones.[33]

Antibiotics

Long-term rather than short-term antibiotics should be used. Despite appropriate antibiotic use, therapy may eradicate carriage in only 80% of cases.[115] The type of antibiotic therapy is similar to that used for S Typhi: amoxicillin, trimethoprim/sulfamethoxazole, or ciprofloxacin.[45][115][116][117] The latter 2 antibiotics have superior penetration capabilities and may be the preferred agents.[118][119] Many providers opt for a fluoroquinolone given the possibility of resistance to other agents and the shorter treatment duration.[120] The choice of the antibiotic should ultimately be based on sensitivity testing of the colonizing isolate.

Praziquantel

Patients with co-existing S haematobium infection should be treated with praziquantel before antibiotic therapy.[33]

Surgery

Carriage of Salmonella may persist in the setting of concurrent gallstones.[33] Cholecystectomy is recommended, especially if chronic carrier state persists despite antibiotic therapy.[121]

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