It has long been said that, in 1885, pioneering American veterinary scientist, Daniel E. Salmon, discovered the first strain of Salmonella.  Actually, Theobald Smith, research-assistant to Dr. Salmon, discovered the first strain of SalmonellaSalmonella cholerae suis.  But, being the one in charge, Dr. Salmon got all the credit.  In any case, today the number of known strains of the bacteria totals over two thousand.  In recent years, concerns have been raised, as particular strains of the bacteria have become resistant to traditional antibiotics, in both animals and humans.

The term Salmonella refers to a group or family of bacteria that variously cause illness in humans.  The taxonomy and nomenclature of Salmonella have changed over the years and are still evolving.  Currently the Centers for Disease Control and Prevention (CDC) recognizes two species which are divided into seven subspecies.  These subspecies are divided into over 50 serogroups based on somatic (O) antigens present.  The most common Salmonella serogroups are A, B, C, D, E, F, and G.  Serogroups are further divided into over 2,500 serotypes.  Salmonella serotypes are typically identified through a series of tests of antigenic formulas listed in a document called the Kauffmann-White Scheme published by the World Health Organization Collaborating Centre for Reference and Research on Salmonella.[1]

Three serotypes–Enteriditis, Typhimurium, and Newport–have persisted as the serotypes most often isolated in patients and reported to the CDC over the last decade.  In 2009 these three serotypes accounted for 42% of all reported cases of Salmonella.[2]  Other serotypes are less common.  For example, that same year Salmonella serotype Braenderup ranked 11th out of reported Salmonella serotypes, accounting for only 720 cases of the 40,828 reported Salmonella cases that year.[3]

A.             Where Does Salmonella Come From?

Salmonella is an enteric bacterium, which means that it lives in the intestinal tracts of humans and other animals, including birds.  Salmonella bacteria are usually transmitted to humans by eating foods contaminated with animal feces or foods that have been handled by infected food service workers who have practiced poor personal hygiene.  Contaminated foods usually look and smell normal.  Contaminated foods are often of animal origin, such as beef, poultry, milk, or eggs, but all foods, including vegetables, may become contaminated. Many raw foods of animal origin are frequently contaminated, but thorough cooking kills Salmonella.  The food handler who neglects to thoroughly wash his or her hands with soap and warm water after using the bathroom may contaminate foods that have otherwise been properly prepared.

B.             What are the Symptoms of Salmonellosis?

Once in the lumen of the small intestine, the bacteria penetrate the epithelium, multiply, and enter the blood within 24 to 72 hours.  Variables such as the health and age of the host and virulence differences among the serotypes affect the nature of the diagnosis.  Infants, the elderly, individuals hospitalized, and the immune-suppressed are the populations that are the most susceptible to disease and suffer the most severe symptoms.

“The majority of persons infected with Salmonella have diarrhea, fever, and abdominal cramps 12-72 hours after exposure.  The illness usually lasts 4-7 days, and the majority of persons recover without treatment.” MMWR Weekly, supra at 684. However, much longer incubation periods of 120 hours to 31 days have been documented in previous Salmonella outbreaks.[4]

The acute symptoms of Salmonella gastroenteritis include the sudden onset of nausea, abdominal cramping, and bloody diarrhea with mucous. As already noted, there is no real cure for a Salmonella infection; treatment, therefore, tends to be palliative – although prescription of antibiotics is common, even if usually contraindicated.

Medical treatment is acutely important if the patient becomes severely dehydrated or if the infection spreads from the intestines. Persons with severe diarrhea often require re-hydration, usually with intravenous fluids.  Antibiotics are not necessary or indicated unless the infection spreads from the intestines, and then it can be treated with ampicillin, gentamicin, trimethoprim/sulfamethoxazole, or ciprofloxacin. Unfortunately, some Salmonella bacteria have become resistant to antibiotics, largely as a result of the use of antibiotics to promote the growth of feed animals.


A.        Reactive Arthritis

The term reactive arthritis refers to an inflammation of one or more joints, following an infection localized at another site distant from the affected joints.  The predominant site of the infection is the gastrointestinal tract.  Several bacteria, including Salmonella, induce septic arthritis.[5] The resulting joint pain and inflammation can resolve completely over time or permanent joint damage can occur.[6]

The reactive arthritis associated with Reiter’s may develop after a person eats food that has been tainted with bacteria. In a small number of persons, the joint inflammation is accompanied by conjunctivitis (inflammation of the eyes), and uveitis (painful urination). Id.  This triad of symptoms is called Reiter’s Syndrome.[7] Reiter’s syndrome, a form of reactive arthritis, is an uncommon but debilitating syndrome caused by gastrointestinal or genitourinary infections. The most common gastrointestinal bacteria involved are Salmonella, Campylobacter, Yersinia, and Shigella. Reiter’s syndrome is characterized by a triad of arthritis, conjunctivitis, and urethritis, although not all three symptoms occur in all affected individuals.[8]

Although the initial infection may not be recognized, reactive arthritis can still occur. Reactive arthritis typically involves inflammation of one joint (monoarthritis) or four or fewer joints (oligoarthritis), preferentially affecting those of the lower extremities; the pattern of joint involvement is usually asymmetric. Inflammation is common at enthuses—i.e., the places where ligaments and tendons attach to bone, especially the knee and the ankle.

Salmonella has been the most frequently studied bacteria associated with reactive arthritis. Overall, studies have found rates of Salmonella-associated reactive arthritis to vary between 6 and 30%.[9]  The frequency of post-infectious Reiter’s syndrome, however, has not been well described.  In a Washington State study, while 29% developed arthritis, only 3% developed the triad of symptoms associated with Reiter’s syndrome.[10]  In addition, individuals of Caucasian descent may be more likely those of Asian descent to develop reactive arthritis,[11] and children may be less susceptible than adults to reactive arthritis following infection with Salmonella.[12]

A clear association has been made between reactive arthritis and a genetic factor called the human leukocyte antigen (HLA) B27 genotype. HLA is the major histocompatibility complex in humans; these are proteins present on the surface of all body cells that contain a nucleus, and are in especially high concentrations in white blood cells (leukocytes). It is thought that HLA-B27 may affect the elimination of the infecting bacteria or an individual’s immune response.[13] HLA-B27 has been shown to be a predisposing factor in one-half to over two-thirds of individuals with reactive arthritis.[14]  While HLA-B27 does not appear to predispose to the initial infection itself, it increases the risk of developing arthritis that is more likely to be severe and prolonged. This risk may be slightly greater for Salmonella and Yersinia-associated arthritis than with Campylobacter, but more research is required to clarify this.[15]

B.        Irritable Bowel Syndrome

A recently-published study surveyed the extant scientific literature and noted that post-infectious irritable bowel syndrome (PI-IBS) is a common clinical phenomenon first-described over five decades ago.[16]  The Walkerton Health Study (WHS) further notes that:

Between 5% and 30% of patients who suffer an acute episode of infectious gastroenteritis develop chronic gastrointestinal symptoms despite clearance of the inciting pathogens.[17]

In terms of its own data, the “study confirm[ed] a strong and significant relationship between acute enteric infection and subsequent IBS symptoms.”[18]  The WHS also identified risk-factors for subsequent IBS, including:  younger age; female sex; and four features of the acute enteric illness—diarrhea for > 7days, presence of blood in stools, abdominal cramps, and weight loss of at least ten pounds.[19]

Irritable bowel syndrome (IBS) is a chronic disorder characterized by alternating bouts of constipation and diarrhea, both of which are generally accompanied by abdominal cramping and pain.[20]  In one recent study, over one-third of IBS sufferers had had IBS for more than ten years, with their symptoms remaining fairly constant over time.[21]  IBS sufferers typically experienced symptoms for an average of 8.1 days per month.[22]

As would be expected from a chronic disorder with symptoms of such persistence, IBS sufferers required more time off work, spent more days in bed, and more often cut down on usual activities, when compared with non-IBS sufferers.[23]  And even when able to work, a significant majority (67%), felt less productive at work because of their symptoms.[24]  IBS symptoms also have a significantly deleterious impact on social well-being and daily social activities, such as undertaking a long drive, going to a restaurant, or taking a vacation.[25]  Finally, although a patient’s psychological state may influence the way in which he or she copes with illness and responds to treatment, there is no evidence that supports the theory that psychological disturbances in fact cause IBS or its symptoms.[26]


Morbidity and mortality in the elderly from infectious disease, generally, is far greater than in other populations.  For instance, death rates for infectious diarrheal disease alone are five (5) times higher in people over 74 years of age than in the next highest group, children under four (4) years of age, and fifteen times higher than the rates seen in younger adults.  Published studies attribute the elderly’s heightened risks, both of infection and mortality due to enteric infectious disease, to several factors:  (1) the aging of the gastrointestinal tract (reduced gastric acidity/reduced gastric motility); (2) a higher prevalence of underlying medical disorders (co-morbidity factors); and (3) malnutrition and a decline in the immune response that leaves the host less able to defend itself against infectious agents.

A.        Aging of the Gastrointestinal Tract—An Invitation to Infection

Inflammation and shrinkage of the gastric mucosa increase with age.  These changes lead to low gastric acidity.  In patients with gastric ulcer disease, the drugs used to treat the condition further block gastric acid production.  Because stomach acids play an important role in limiting the number of bacteria that enter the small intestine, low gastric acidity increases the likelihood of infection if a pathogen is ingested with food or water.

Gastrointestinal motility (peristalsis) decreases with age.  Peristalsis, which is the mechanism that propels the stomach contents through the intestinal tract, is also the mechanical means for removing ingested, life-threatening pathogens.  The risk of infection by potentially invasive pathogens corresponds with the duration of contact between the pathogen and the intestinal mucosa.  Thus, a decrease in peristalsis delays the clearance of the pathogen from the intestinal tract and contributes substantially to the increased prevalence and severity of infection in the elderly.

B.        A Higher Prevalence of Underlying Medical Conditions—Co-Morbidity Factors

Underlying medical conditions or disease (co-morbid factors) also contribute to the morbidity and mortality of infection in the elderly.  Among hospitalized patients, those older than 65 develop pneumonia twice as often as younger patients due to poor nutrition, neuromuscular disease (poor cough reflex and aspiration), pharyngeal colonization, depressed level of alertness, endotracheal intubation, intensive care unit admission, nasogastric tube use, and antacid use.  Pneumonia is the leading infectious cause of death in the elderly.

Atherosclerosis, another common co-morbid disease, compromises circulation and blood flow to the peripheral tissues and the skin, particularly in elderly individuals who are hospitalized and bedridden with an infectious illness.  Unfortunately, it is the skin and the previously discussed mucous membranes that serve as the body’s first line of defense against invasion by infectious microorganisms.  Loss of the integrity of the skin may result in the development of pressure ulcers, which are warm, moist mediums for infectious microorganisms to rapidly multiply and are associated with a number of infectious complications.

When an infectious microorganism, regardless of source, gains access to the bloodstream, the patient may develop systemic sepsis, also known as bacteremia.  Bacteremia is most common in people who are already affected by, or are being treated for, some other medical problem (co-morbid disease); conversely, people in good health with strong immune systems rarely develop bacteremia.  The main sources of bacteremia in elderly patients are the urinary tract, gastrointestinal tract, respiratory tract, and the skin.  Other potential sources include surgical wounds, invasive tubes and catheters, intravenous lines—virtually any site where an invasive medical procedure has occurred.  Bacterial organisms most likely to cause bacteremia include members of the Staphylococcus, Streptococcus, and Escherichia coli genera.  Because bacteremia is far more prevalent in those with co-morbid conditions, which group is substantially populated by the elderly, the presence of co-morbid conditions is clearly a determinant of the mortality associated with infectious disease.

C.        A Weakened Immune System—the Inability to Fight off Infection

With advancing age come progressive weakness, decline, and dysfunction of the immune system.  Many of the body’s natural physiologic responses to infection are therefore blunted in the elderly; and the intensity of many clinical signs and symptoms in an elderly patient with an infectious process are heightened when compared to those in a younger person.  This age-related decline contributes significantly to the increased risk of severe illness and mortality in elderly persons with infectious disease.

The effect of a weakened immune response on the health of an elderly person often manifests most apparently during periods of intense stress (e.g., surgery, sepsis, multiple organ failure, malnutrition, dehydration).

[1]           Grimont, PAD, Weill, F. Antigenic formulae of the Salmonella serovars, 2007, 9th Edition. WHO Collaborating Centre for Reference and Research on Salmonella. Paris: Pasteur Institute. http://www.pasteur.fr/ip/portal/action/WebdriveActionEvent/oid/01S-000036-089.

[3]           Id.

[4]           O’ Mahony, et al., An outbreak of Salmonella Heidelberg infection associated with a long incubation period, J. Public Health (1990) 12 (1): 19-21;  Abe, et al., Prolonged Incubation Period of Salmonellosis Associated with Low Bacterial Doses, J. Food Protection (2004) Vol. 67, No. 12; 2735-2740.

[5]           See J. Lindsey, “Chronic Sequellae of Foodborne Disease,” Emerging Infectious Diseases, Vol. 3, No. 4, Oct-Dec, 1997.

[6]           Id.

[7]           Id. See also, Dworkin, et al., “Reactive Arthritis and Reiter’s Syndrome following an outbreak of gastroenteritis caused by Salmonella enteritidis,” Clin. Infect. Dis., 2001 Oct. 1;33(7): 1010-4; Barth, W. and Segal, K., “Reactive Arthritis (Reiter’s Syndrome),” American Family Physician, Aug. 1999, online at www.aafp.org/afp/990800ap/499.html.

[8]           Hill Gaston JS, Lillicrap MS.  (2003).  Arthritis associated with enteric infection. Best Practices & Research Clinical Rheumatology.  17(2):219-239.

[9]           Id.

[10]          Dworkin MS, Shoemaker PC, Goldoft MJ, Kobayashi JM.  “Reactive arthritis and Reiter’s syndrome following an outbreak of gastroenteritis caused by Salmonella enteritidis.  Clin. Infect. Dis. 33(7):1010-1014.

[11]          McColl GJ, Diviney MB, Holdsworth RF, McNair PD, Carnie J, Hart W, McCluskey J, “HLA-B27 expression and reactive arthritis susceptibility in two patient cohorts infected with Salmonella Typhimurium,”  Australian and New Zealand Journal of Medicine 30(1):28-32 (2001).

[12]          Rudwaleit M, Richter S, Braun J, Sieper J, “Low incidence of reactive arthritis in children following a Salmonella outbreak,” Annals of the Rheumatic Diseases. 60(11):1055-1057 (2001).

[13]          Hill Gaston and Lillicrap, supra Note 7.

[14]          Id.; Barth WF, Segal K., “Reactive arthritis (Reiter’s syndrome).” American Family Physician.  60(2):499-503, 507 (1999).

[15]          Hill Gaston and Lillicrap, supra Note 7.

[16]          J. Marshall, et al., Incidence and Epidemiology of Irritable Bowel Syndrome After a Large Waterborne Outbreak of Bacterial Dysentery, Gastro., 2006; 131;445-50 (hereinafter “Walkerton Health Study” or “WHS”). The WHS followed one of the largest E. coli O157:H7 outbreaks in the history of North America. Contaminated drinking water caused over 2,300 people to be infected with E. coli O157:H7, resulting in 27 recognized cases of HUS, and 7 deaths. Id. at 445.  The WHS followed 2,069 eligible study participants. Id.  For Salmonella specific references, see Smith, J.L., Bayles, D.O., Post-Infectious Irritable Bowel Syndrome: A Long Term Consequence of Bacterial Gastroenteritis, Journal of Food Protection. 2007:70(7);1762-1769.

[17]          Id. at 445 (citing multiple sources).

[18]          WHS, supra note 34, at 449.

[19]          Id. at 447.

[20]          A.P.S. Hungin, et al., Irritable Bowel Syndrome in the United States: Prevalence, Symptom Patterns and Impact, Aliment Pharmacol. Ther. 2005:21 (11); 1365-75.

[21]          Id. at 1367.

[22]          Id.

[23]          Id. at 1368.

[24]          Id.

[25]          Id.

[26]          Amy Foxx-Orenstein, DO, FACG, FACP, IBS—Review and What’s New, General Medicine 2006:8(3) (Medscape 2006) (collecting and citing studies).  Indeed, PI-IBS has been found to be characterized by more diarrhea but less psychiatric illness with regard to its pathogenesis. See Nicholas J. Talley, MD, PhD, Irritable Bowel Syndrome: From Epidemiology to Treatment, from American College of Gastroenterology 68th Annual Scientific Meeting and Postgraduate Course (Medscape 2003).

Salmonella:  Marler Clark, The Food Safety Law Firm, is the nation’s leading law firm representing victims of Salmonella outbreaks. The Salmonella lawyers of Marler Clark have represented thousands of victims of Salmonella and other foodborne illness outbreaks and have recovered over $600 million for clients.  Marler Clark is the only law firm in the nation with a practice focused exclusively on foodborne illness litigation.  Our Salmonella lawyers have litigated Salmonella cases stemming from outbreaks traced to a variety of foods, such as cantaloupe, tomatoes, ground turkey, salami, sprouts, cereal, peanut butter, and food served in restaurants.  The law firm has brought Salmonella lawsuits against such companies as Cargill, ConAgra, Peanut Corporation of America, Sheetz, Taco Bell, Subway and Wal-Mart.

If you or a family member became ill with a Salmonella infection, including Reactive Arthritis or Irritable bowel syndrome (IBS), after consuming food and you’re interested in pursuing a legal claim, contact the Marler Clark Salmonella attorneys for a free case evaluation.