Salmonella enterica subspecies enterica is a gram-negative, rod-shaped bacillus. More than 2,500 Salmonella serotypes have been identified. Nontyphoidal salmonellosis refers to illnesses caused by all serotypes of Salmonella except for Typhi, Paratyphi A, Paratyphi B (tartrate negative), and Paratyphi C.
Usually through the consumption of food or water contaminated with animal feces. Transmission can also occur through direct contact with infected animals or their environment and directly between humans.
Nontyphoidal salmonellae are a leading cause of bacterial diarrhea worldwide; they are estimated to cause 94 million cases of gastroenteritis and 115,000 deaths globally each year. The risk of Salmonella infection among travelers returning to the United States varies by region of the world visited. In one analysis, the incidence of laboratory-confirmed infections from 2004 through 2009 was 7.1 cases per 100,000 among travelers to Latin American and Caribbean, 5.8 cases per 100,000 among travelers to Asia, and 25.8 cases per 100,000 among travelers to Africa. The true number of illnesses is much higher, because most ill people do not have a stool specimen tested. Travelers with salmonellosis were most likely to report visiting the following countries: Mexico (38% of travel-associated salmonellosis), India (9%), Jamaica (7%), the Dominican Republic (4%), China (3%), and the Bahamas (2%). Salmonella infection and carriage has been reported among internationally adopted children.
Gastroenteritis is the most common clinical presentation of nontyphoidal Salmonella infection. The incubation period of nontyphoidal salmonellosis is 6–72 hours, but illness usually occurs within 12–36 hours after exposure. Illness is commonly manifested by acute diarrhea, abdominal pain, fever, and sometimes vomiting. The illness usually lasts 4–7 days, and most people recover without treatment. Approximately 5% of people develop bacteremia or focal infection (such as meningitis or osteomyelitis). Salmonellosis outcomes differ by serotype. Infections with some serotypes, including Dublin and Choleraesuis, are more likely to result in invasive infections. Rates of invasive infections and death are generally higher among infants, older adults, and people with immunosuppressive conditions (including HIV), hemoglobinopathies, and malignant neoplasms.
Diagnosis is based on isolation of Salmonella organisms. About 90% of isolates are obtained from routine stool culture, but isolates are also obtained from blood, urine, and material from sites of infection. Isolates of salmonellae are needed for serotyping and antimicrobial susceptibility testing.
Current recommendations are to treat most patients with uncomplicated Salmonella infection with supportive therapy and no antimicrobial agents. Antimicrobial therapy should be considered for patients who are severely ill (for example, those with severe diarrhea, high fever, or manifestations of extraintestinal infection) and for gastroenteritis caused by Salmonella species in people at increased risk of invasive disease (infants aged <3 months, older adults aged ≥60 years, and the debilitated or immunosuppressed). Fluoroquinolones are often employed for empiric treatment of patients with moderate to severe travelers’ diarrhea; azithromycin and rifaximin are also commonly used. Resistance to antimicrobial agents varies by serotype and geographic region. Resistance to older antimicrobial agents (chloramphenicol, ampicillin, and trimethoprim-sulfamethoxazole) has been present for many years, and resistance to both fluoroquinolones and third-generation cephalosporins has increased.
No vaccine is available against nontyphoidal Salmonella infection. Preventive measures are aimed at avoiding foods and drinks at high risk for contamination; frequent handwashing, especially after contacting animals or their environment; and taking additional food and water precautions while traveling (see Chapter 2, Food & Water Precautions).
American Academy of Pediatrics. Salmonella infections. In: Pickering LK, editor. Red Book: 2012 Report of the Committee on Infectious Diseases. 29th ed. Elk Grove Village, IL: American Academy of Pediatrics; 2012. p. 635–40.
American Public Health Association. Salmonellosis. In: Heymann DL, editor. Control of Communicable Diseases Manual. 19th ed. Washington, DC: American Public Health Association; 2008. p. 534–40.
Galanis E, Lo Fo Wong DM, Patrick ME, Binsztein N, Cieslik A, Chalermchikit T, et al. Web-based surveillance and global Salmonella distribution, 2000–2002. Emerg Infect Dis. 2006 Mar;12(3):381–8.
Johnson LR, Gould LH, Dunn JR, Berkelman R, Mahon BE, FoodNet Travel Working Group. Salmonella infections associated with international travel: a Foodborne Diseases Active Surveillance Network (FoodNet) study. Foodborne Pathog Dis. 2011 Sep;8(9):1031–7.
Jones TF, Ingram LA, Cieslak PR, Vugia DJ, Tobin-D’Angelo M, Hurd S, et al. Salmonellosis outcomes differ substantially by serotype. J Infect Dis. 2008 Jul 1;198(1):109–14.
Kendall ME, Crim S, Fullerton K, Han PV, Cronquist AB, Shiferaw B, et al. Travel-associated enteric infections diagnosed after return to the United States, Foodborne Diseases Active Surveillance Network (FoodNet), 2004–2009. Clin Infect Dis. 2012 Jun;54 Suppl 5:S480–7.
Majowicz SE, Musto J, Scallan E, Angulo FJ, Kirk M, O’Brien SJ, et al. The global burden of nontyphoidal Salmonella gastroenteritis. Clin Infect Dis. 2010 Mar 15;50(6):882–9.
Medalla F, Hoekstra RM, Whichard JM, Barzilay EJ, Chiller TM, Joyce K, et al. Increase in resistance to ceftriaxone and nonsusceptibility to ciprofloxacin and decrease in multidrug resistance among Salmonella strains, United States, 1996–2009. Foodborne Pathog Dis. 2013 Apr;10(4):302–9.
Paredes-Paredes M, Flores-Figueroa J, Dupont HL. Advances in the treatment of travelers’ diarrhea. Curr Gastroenterol Rep. 2011 Oct;13(5):402–7.