Overview of foodborne illness (E. coli and Campylobacter)

Widespread, deadly, and underreported

Foodborne pathogens are common and opportunistic; they disproportionately affect children, the elderly, and immunocompromised individuals.

Despite a sophisticated nationwide surveillance and reporting network, it is difficult to draw an accurate picture of foodborne illness in the United States. In 2006 there were 1,270 foodborne disease outbreaks, resulting in a reported 27,634 cases and 11 deaths.¹ And the CDC admits these numbers may not be complete and accurate. “The number of reported cases of diseases under surveillance is a vast underestimate of the true burden, because most episodes of disease never reach the reporting system.”²

The World Health Organization estimates that in 2005, 1.8 million people worldwide died from diarrheal diseases. The majority are foodborne. Many children in developing countries suffer from malnutrition as a consequence of diarrheal disease.³

E. coli pathogenesis

E. coli bacteria are natural inhabitants of the human body, colonizing the digestive tracts of neonates within hours of birth.⁴ The bacteria enjoy a symbiotic relationship with their hosts. Highly adaptable, E. coli can thrive in anaerobic and aerobic environments, sense chemical and temperature changes, and grow fimbriae to attach to mucosal surfaces.⁵

There are more than 700 known E. coli serotypes, which are characterized by their expression of O, H, and K antigens.⁴ Pathogenic E. coli are diarrheagenic and fall into distinct categories according to their mechanism of pathogenesis.⁴ Recent E. coli outbreaks have been traced to ground beef, leafy vegetables (including spinach), packaged cookie dough, and pizza.

Enterohemorrhagic E. coli (EHEC)

Enterohemorrhagic E. coli, so named because they cause bloody diarrhea, are found in humans, cattle, and goats. Some serotypes can produce Shiga toxins (STx) and are referred to as Shiga toxigenic E. coli (STEC). STEC are associated with significant morbidity and mortality. The STEC serotype O157:H7 has been isolated in many outbreaks.⁴ However there is growing concern over non-O157 Shiga toxin producing E. coli, which now cause about 50% of all STEC infections.^6,7

STEC infection

Infection by Shiga toxin producing E. coli (STEC), including serotype O157:H7 and non-O157, poses the greatest risk of serious disease and potential fatality.

STEC remain in the GI tract, but the Shiga toxin causes a number of pathological effects, most importantly on vascular endothelial cells. STEC infection can result in:

• No effects at all
• Watery diarrhea, sometimes accompanied by abdominal pain, nausea, and vomiting
• Hemorrhagic colitis, characterized by bloody diarrhea
• Hemolytic uremic syndrome (HUS) in about 5% to 8% of pediatric patients with hemorrhagic colitis⁸
  • HUS is characterized by acute renal failure
  • HUS is potentially fatal
  • HUS can result in permanently compromised kidney function

According to the CDC, of 3,464 patients with STEC infection⁹:

• 42% were hospitalized
• 6.3% suffered hemolytic uremic syndrome (HUS)
• 0.6% died (5% mortality rate for HUS patients)⁹

Campylobacter pathogenesis

Campylobacter is the leading bacterial cause of gastroenteritis (often called “stomach flu”) and diarrhea in the developed world.^10,11 Campylobacter accounts for 5% to 7% of all cases of gastroenteritis in the U.S.¹²

Two species of Campylobacter, C. jejuni and C. coli, are common human pathogens. C. jejuni is the most common isolate and there is evidence to suggest that the species might take different routes to infection depending on ethnicity, type of food eaten, and travel destinations.¹³

Campylobacter infection is sporadic and not driven by outbreak. About 50% of the cases are attributable to handling and eating poultry.¹⁰ The infection is substantially underreported; the CDC estimates that campylobacterosis affects 2.4 million Americans each year including an estimated 124 deaths.¹¹

Campylobacter infection (campylobacterosis)

Campylobacter produces two toxins¹⁴:

• Enterotoxins which disturb water regulation in the GI tract and cause diarrhea
• Cytoxins closely related to Shiga toxin, which are letal to epithelial cells in the gut and can activate inflammatory mediators ^14,15

In addition to diarrhea, symptoms of campylobacterosis include:

• Bloody diarrhea (usually occult)
• Abdominal pain
• Nausea
• Fever
• Headache
• Muscle pain¹⁶

While the majority of cases resolve without intervention in two to five days,¹¹ Campylobacter can cause serious and long-term consequences, including¹¹:

• Bacteremia (attributable primarily to C. fetus)¹²
• Gullain-Barre Syndrome (an autoimmune inflammatory disease affection the peripheral nervous system) in about 1 out of every 1,000 cases of campylobacterosis¹¹

Diagnosing E. coli and Campylobacter infections