Fundamental Food Microbiology, Third Edition - Fuad Fathir

372 FUNDAMENTAL FOOD MICROBIOLOGY
3. Enteroinvasive Esc. coli (EIEC)
These strains are known to cause dysentery similar to that that caused in shigellosis.
The ability of the strains to produce an invasive factor is thought to be the cause of
the disease. Human carriers, directly or indirectly, spread the disease. Ingestion of
as many as 10 6 cells may be necessary for an individual to develop symptoms. An
outbreak in the U.S. as early as 1971 was recognized from the consumption of
imported Camembert cheese contaminated with serotype O124:B17.
4. Enterohemorrhagic Esc. coli (EHEC)
The strains in this group (a principal serogroup is O157:H7) have been recognized
relatively recently as the cause of severe bloody diarrhea (hemorrhagic colitis) and
hemorrhagic uremic syndrome (HUS) in humans. Animals, particularly dairy cattle,
are thought to be the carriers. Ingestion of as few as 10 to 100 cells can produce
the disease, especially in sensitive individuals. Three enterotoxins (verotoxins) produced
by the serotype cause the disease symptoms.
Although there is no clear differentiation for these four subgroups, both EIEC
and EHEC strains seem to fit with the enteric pathogens associated with foodborne
infection. Thus, these two groups are discussed in this chapter. Both EPEC and
ETEC groups are included in Chapter 26, under toxicoinfection.
B. Gastroenteritis Due to EIEC
1. Toxins
The pathogens produce several polypeptides, the genes of which are encoded in a
plasmid. These are considered to be the invasive factors that enable the pathogen to
invade epithelial cells and set up infection in the colon. Separate toxins have not yet
been identified. 16,17
2. Disease and Symptoms
The disease and symptoms are similar to those for shigellosis. Following ingestion
of the pathogen (ca. 10 6 cells) and incubation period, symptoms appear as abdominal
cramps, profuse diarrhea, headache, chills, and fever. A large number of pathogens
are excreted in the feces. Symptoms can last for 7 to 12 d, but a person can remain
a carrier and shed the pathogens in feces for a long time. 16,17
3. Food Association
Only humans are known to be the host of the pathogen, and a food can get contaminated
directly or indirectly though fecal contamination. Outbreaks from the ingestion
of foods contaminated with the pathogen have been recorded. The 1971 outbreak
in the U.S. from the ingestion of an imported cheese was traced to contamination
of the processing plant equipment from a malfunctioning water filtration system. In
1983, another outbreak on a cruise ship was related to potato salad contaminated
by a carrier food handler. 16,17