NONTYPHOIDAL SALMONELLA INFECTIONS
 Salmonellae are motile, gram-negative, rod-shaped bacteria of the family Enterobacteriaceae.
 Most frequently isolated Salmonella strains causing human disease:
o S enteritidis (26.1%)
o S typhimurium (22.1%)
o S enteritidis heidelberg (4.8%)
o Salmonella enteritidis newport (4.3%)
 Most types of Salmonella live in the intestinal tracts of animals and birds and are transmitted to
humans by contaminated foods of animal origin. The most common sources of salmonellae are
beef, poultry, and eggs.
 Stringent procedures for cleaning and inspecting eggs were implemented in the 1970s and have
made salmonellosis caused by external fecal contamination of egg shells extremely rare.
 However, unlike eggborne salmonellosis of past decades, the current epidemic is due to intact
and disinfected grade A eggs. The reason for this is that Salmonella enteritidis silently infects
the ovaries of healthy appearing hens and contaminates the eggs before the shells are formed.
Only a small number of hens seem to be infected at any given time, and an infected hen can lay
many normal eggs while only occasionally laying an egg contaminated with the Salmonella
bacterium. Salmonella enteritidis, can be inside perfectly normal-appearing eggs, and if the
eggs are eaten raw or undercooked, the bacterium can cause illness. Also keeping eggs
adequately refrigerated prevents any Salmonella present in the eggs from growing to higher
numbers. Commercially manufactured ice cream and eggnog are made with pasteurized eggs
and have not been linked with Salmonella enteritidis infections.
 Salmonellae attach to and invade the intestine, survive within phagosomes, effect massive
efflux of electrolytes and water into the intestinal lumen.
Symptoms and Signs
 The elderly, infants, and those with impaired immune systems may have a more severe illness.
o In these patients, the infection may spread from the intestines to the blood stream, and
then to other body sites and can cause death unless the person is treated promptly with
antibiotics.
Salmonella infection may present clinically as gastroenteritis, bacteremic syndrome, focal disease,
asymptomatic carrier state.
Gastroenteritis
 usually starts 6-12 to 48-72 hours after consuming a contaminated food or beverage
 fever (38-39°C)
 nausea, sometimes vomiting, abdominal cramps, followed by diarrhea
 stools are loose and bloodless
 Salmonellae may rarely cause large-volume choleralike diarrhea or may be associated with
tenesmus.
 The disease is usually mild, lasting 1 to 4-7 days.
 most persons recover without antibiotic treatment
 In stool specimens stained with methylene blue, WBCs are often seen, indicating inflammatory
colitis.
 Diagnosis is confirmed by culturing Salmonella from stool specimens or rectal swabs.
Focal manifestations of Salmonella infection may occur with or without sustained bacteremia. In
patients with bacteremia, localized infection may occur, involving the:
 GI tract (liver, gallbladder and appendix),
 Cardiovascular: Salmonella infections (commonly S typhimurium or S choleraesuis) may
produce arterial infections or endocarditis.
 Pulmonary: Salmonella pneumonia or empyema is rare in the absence of comorbid illnesses
such as underlying lung disease, malignancy, diabetes, sickle cell anemia, or alcohol abuse.

Genitourinary: Individuals with urolithiasis or structural abnormalities or individuals who are
undergoing immunosuppressive therapy are predisposed to Salmonella urinary tract infections.
 Neurologic: Salmonella meningitis may rarely occur, typically in infants and young children.
 Skeletal: Infection with salmonellae may cause septic arthritis and osteomyelitis. The latter
affects the long bones and typically occurs in patients with sickle cell disease.
Bacteremia is relatively uncommon in patients with gastroenteritis. However, S. choleraesuis, S.
typhimurium, and S. heidelberg, among others, can cause a sustained bacteremic syndrome lasting >=
1 wk. Although blood cultures are positive, stool cultures are generally negative. Patients with AIDS
or HIV infection may have recurrent episodes of bacteremia or other invasive infections (eg, septic
arthritis) due to Salmonella. Multiple Salmonella infections in a patient without other risk factors
should prompt HIV testing.
Carriers do not appear to play a major role in large outbreaks of nontyphoidal gastroenteritis.
Persistent shedding of organisms in the stool for >= 1 yr occurs in only 0.2 to 0.6% of patients with
nontyphoidal Salmonella infections.
Chronic consequences -- reactive arthritis and Reiter's syndrome symptoms may follow 3-4 weeks
after onset of acute symptoms. Reactive arthritis may occur with a frequency of about 2% of cultureproven cases. Septic arthritis, subsequent or coincident with septicemia, also occurs and can be
difficult to treat.
Lab Studies:
 Bacteriology
Freshly passed stool is the preferred specimen for the isolation of nontyphoidal Salmonella species. A
variety of selective media is routinely employed, including MacConkey, eosin-methylene blue (EMB)
agar, Hektoen enteric (HE) agar, Salmonella-Shigella (SS) agar, and xylose-lysine-deoxycholate
(XLD) agar.
Salmonella species may be differentiated by conventional biochemical assays and serological typing.
 Other Tests
Specialized laboratories may employ phage typing, plasmid analysis, ribotyping, pulsed field gel
electrophoresis, and polymerase chain reaction when diagnosing salmonellosis.
Prophylaxis and Treatment
 Poultry, meat, eggs, and other foods must be properly cooked, handled, stored, and refrigerated.
 Gastroenteritis is treated symptomatically with fluids, electrolyte replacement and bland diet.
 Antibiotics prolong excretion of the organism and are unwarranted in uncomplicated cases.
 Elderly nursing home residents, infants, and patients with HIV infection or AIDS should be
treated with antibiotics. Antibiotic resistance is more common with nontyphoidal Salmonella.
o TMP-SMX, 5 mg/kg of TMP component po every 12 h for children, or
o Ciprofloxacin 500 mg po q 12 h for adults, or
o Amoxicillin1 g PO q8h for 3-7 d, or
o Chloramphenicol (Chloromycetin) 500 mg PO/IV qid for 3-7 d
 Nonimmunocompromised patients should be treated for 3 to 5 days, but those with AIDS may
require prolonged suppression to prevent relapses.
 Systemic or focal disease should be treated with antibiotic. Sustained bacteremia is generally
treated for 4 to 6 wk. Abscesses should be drained surgically; at least 4 wk of antibiotic therapy
should follow surgery.
 Asymptomatic carriage is usually self-limited, and antibiotic treatment is rarely required.
Antibiotics can prolong the shedding of organisms in the stool after the drug has been
discontinued. In unusual cases (eg, in food handlers or health care workers), eradication may be
attempted with ciprofloxacin 500 mg po q 12 h for 1 mo, but follow-up stool cultures should be
obtained in the weeks after drug administration to document elimination of Salmonella.
o Current recommendations are that antibiotics should be reserved for patients with
severe disease or patients who are at high risk of invasive disease.
o
If an antibiotic is indicated, treatment with an oral quinolone, trimethoprimsulfamethoxazole, or amoxicillin (1 g PO q8h for 3-7 d) for 48-72 hours or until
defervescence is usually adequate.
Complications:
 Cardiovascular - Endocarditis, pericarditis, valve perforation, and arteritis
 CNS - Meningitis, ventriculitis, and abscess
 Pulmonary - Pneumonia, abscess, empyema, and bronchopleural fistula
 Bone/joints - Osteomyelitis and septic arthritis
 Hepatobiliary - Hepatic abscess, cholecystitis, and peritonitis
 Splenic - Abscess
 Urinary - Cystitis, pyelonephritis, and renal abscess
 Genital - Ovarian abscess, testicular abscess, prostatitis, and epididymitis
 Soft tissue - Abscess
Prognosis:
 Nontyphoidal salmonellosis is generally self-limiting, with symptoms typically lasting no
longer than 3-7 days.
 Salmonellosis may be severe in patients who are debilitated, immunocompromised, or at the
extremes of age
 Patients occasionally require hospitalization, but death is rare (<1%).
 After resolution of symptoms, the mean duration of fecal shedding of Salmonella is 4-5 weeks,
depending on the strain.