682 Modern Food Microbiology
4. In July 1985, 13 of 16 individuals at a picnic in Connecticut met the case definition of giardiasis, and the most likely vehicle food was a noodle salad.
78 Although most victims developed
symptoms between 6 and 20 days after the picnic, the salad preparer became ill the day after
the food was eaten by others. This was the second well-documented common-source outbreak
traced to a food product.
5. In 1988, 21 of 108 members of a church youth group in Albuquerque, New Mexico, were
victims. Taco ingredients were the most likely vehicles from dinners prepared by parents at a
church.
18
The U.S. Centers for Disease Control and Prevention (CDCP) recorded foodborne giardiases outbreaks in 1985 and 1986, with 1 outbreak and 13 cases in 1985 and 2 outbreaks and 28 cases in 1986.
5
The common occurrence of this organism suggests that it may be a more frequent cause of foodborne
infection than is reported. The incubation period of 7 days plus could be a factor in the apparent
underreporting. Another possible factor is the need to demonstrate the organism in stools and leftover
foods by microscopic examination, a practice that is not routine in the microbiological examination
of foods in foodborne gastroenteritis outbreaks.
Amebiasis
Amebiasis (amoebic dysentery), caused by Entamoeba histolytica, is often transmitted by the fecal–
oral route, although transmission is known to occur by water, food handlers, and foods. According to
Jackson
48 there is better documentation of food transmission of amebic dysentery than for the other
intestinal protozoal diseases. The organism is unusual in being anaerobic, and the trophozoites (ameba
stages) lack mitochondria. It is an aerotolerant anaerobe that requires glucose or galactose as its main
respiratory substrate.
69 The trophozoites of E. histolytica range in size from 10 to 60 µm, whereas the
cysts usually range between 10 and 20 µm. The trophozoites are motile; the cysts are not. It is often
found with Entamoeba coli, with which it is associated in the intestine and stools. In warm stools from
a case of active dysentery, E. histolytica is actively motile and usually contains red blood cells that
the protozoan ingests by pseudopodia. Although generally outnumbered in stools by Entamoeba coli,
the latter never ingests red blood cells. Although the trophozoites do not persist under environmental
conditions, the encysted forms can survive as long as 3 months in sewage sludge.
3 A person with this
disease may pass up to 4.5 × 10
7 cysts each day.
3
The possible transmission of cysts to foods becomes a real possibility when poor personal restroom
hygiene is practiced. The incidence of amebiasis varies widely, with a rate of 1.4% reported for
Tacoma, Washington, to 36.4% in rural Tennessee.
19 It is estimated that 10% of the world’s population
is infected with E. histolytica and that up to 100 million cases of amebic colitis or liver abscesses
occur each year.
In its trophozoite stage, the organism induces infection in the form of abscesses in intestinal mucosal
cells and ulcers in the colon. Its adherence to host-cell glycoproteins is mediated by a galactose-specific
lectin. It reproduces by binary fission in the large intestine. It encysts in the ileum, and cysts may occur
free in the lumen. The organism produces an enterotoxic protein with molecular weight of 35,000–
45,000 Da.
19
Syndrome, Diagnosis, and Treatment
The incubation period for amebiasis is 2–4 weeks, and symptoms may persist for several months. Its
onset is often insidious, with loose stools and generally no fever. Mucus and blood are characteristic
4. In July 1985, 13 of 16 individuals at a picnic in Connecticut met the case definition of giardiasis, and the most likely vehicle food was a noodle salad.
78 Although most victims developed
symptoms between 6 and 20 days after the picnic, the salad preparer became ill the day after
the food was eaten by others. This was the second well-documented common-source outbreak
traced to a food product.
5. In 1988, 21 of 108 members of a church youth group in Albuquerque, New Mexico, were
victims. Taco ingredients were the most likely vehicles from dinners prepared by parents at a
church.
18
The U.S. Centers for Disease Control and Prevention (CDCP) recorded foodborne giardiases outbreaks in 1985 and 1986, with 1 outbreak and 13 cases in 1985 and 2 outbreaks and 28 cases in 1986.
5
The common occurrence of this organism suggests that it may be a more frequent cause of foodborne
infection than is reported. The incubation period of 7 days plus could be a factor in the apparent
underreporting. Another possible factor is the need to demonstrate the organism in stools and leftover
foods by microscopic examination, a practice that is not routine in the microbiological examination
of foods in foodborne gastroenteritis outbreaks.
Amebiasis
Amebiasis (amoebic dysentery), caused by Entamoeba histolytica, is often transmitted by the fecal–
oral route, although transmission is known to occur by water, food handlers, and foods. According to
Jackson
48 there is better documentation of food transmission of amebic dysentery than for the other
intestinal protozoal diseases. The organism is unusual in being anaerobic, and the trophozoites (ameba
stages) lack mitochondria. It is an aerotolerant anaerobe that requires glucose or galactose as its main
respiratory substrate.
69 The trophozoites of E. histolytica range in size from 10 to 60 µm, whereas the
cysts usually range between 10 and 20 µm. The trophozoites are motile; the cysts are not. It is often
found with Entamoeba coli, with which it is associated in the intestine and stools. In warm stools from
a case of active dysentery, E. histolytica is actively motile and usually contains red blood cells that
the protozoan ingests by pseudopodia. Although generally outnumbered in stools by Entamoeba coli,
the latter never ingests red blood cells. Although the trophozoites do not persist under environmental
conditions, the encysted forms can survive as long as 3 months in sewage sludge.
3 A person with this
disease may pass up to 4.5 × 10
7 cysts each day.
3
The possible transmission of cysts to foods becomes a real possibility when poor personal restroom
hygiene is practiced. The incidence of amebiasis varies widely, with a rate of 1.4% reported for
Tacoma, Washington, to 36.4% in rural Tennessee.
19 It is estimated that 10% of the world’s population
is infected with E. histolytica and that up to 100 million cases of amebic colitis or liver abscesses
occur each year.
In its trophozoite stage, the organism induces infection in the form of abscesses in intestinal mucosal
cells and ulcers in the colon. Its adherence to host-cell glycoproteins is mediated by a galactose-specific
lectin. It reproduces by binary fission in the large intestine. It encysts in the ileum, and cysts may occur
free in the lumen. The organism produces an enterotoxic protein with molecular weight of 35,000–
45,000 Da.
19
Syndrome, Diagnosis, and Treatment
The incubation period for amebiasis is 2–4 weeks, and symptoms may persist for several months. Its
onset is often insidious, with loose stools and generally no fever. Mucus and blood are characteristic