Food Biochemistry and Food Processing (2 edition)

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41 Microbial Safety of Food and Food Products 793

are reported annually in the United States. Individuals most sus-

ceptible to Listeriosis include the elderly, the young, immuno-

compromised patients, and pregnant woman. A wide variety of

foods including processed meats, milk and dairy products, fruits,

and vegetables have been implicated in a number of Listerioses

outbreaks. In 1999, a multistate outbreak involving 1000 cases

of Listeriosis in the United States was linked to consumption

of contaminated hot dogs and delicatessen meats, resulting in

a recall of 35 million pounds of these food products (MMWR

1999).

VerotoxigenicESCHERICHIA COLI(VTEC)

Infections

VerotoxigenicEscherichia coli(VTEC) belonging to the O157

serogroup is the most common VTEC serogroup implicated in

foodborne disease outbreaks. This organism was first recog-

nized as a cause of hemorrhagic colitis in 1982. VTEC O157

and serogroups O5, O26, and O111 are of high prevalence in fe-

ces of healthy cattle. Thus, foods of animal origin such as meat,

milk, and dairy products can be contaminated with these or-

ganisms. Other types of foods such as salads, vegetables, fruits,

sandwiches, and cooked meat can be contaminated during prepa-

ration. Contaminated water can also be a source of infection by

this organism. The majority of food- and waterborne outbreaks

had links with contamination of fecal origin. Infection by VTEC

can result in hemorrhagic colitis (HC) and hemolytic uremic

syndrome (HUS), abdominal pain, and watery diarrhea (bloody

or nonbloody). The HC symptoms may lead to complications

of the HUS and subsequent renal failure. Although HUS can

occur in any age group, children are more susceptible (Karmali

1989). In adults, 50% of thrombocytopenic purpura (TP) cases

are caused by HUS.

Other bacterial foodborne infections can occur as a result of in-

gestion of food contaminated withStaphylococcus aureustoxin,

Clostridium perfringens, Clostridium botulinumtoxin, Shigella

spp.,Yersinia enterocolitica, Brucellaspp.,Vibrio cholera, Vib-

rio paraheamolylicus, andBacillus cereusenterotoxin.

Foodborne Parasite Infections

Foodborne parasite infections are caused by certain groups of

protozoa. It is believed that foodborne infections related to par-

asites are underreported by an estimated factor of 10 or more

(Casemore 1991), and the etiological agent of foodborne out-

breaks is identified in less than 50% of the cases (Bean et al.

1990, Cliver 1987). Parasites commonly associated with food-

borne disease and possible food and water sources are listed in

Table 41.3.

Cryptosporidium parvumis the species ofCryptosporidium

associated with infection in humans (Current and Blagburn

1990). It is a common cause of gastrointestinal infections in im-

munocompromised individuals and is an opportunistic pathogen

associated with infections in patients with acquired immune

deficiency syndrome (AIDS), but it affects healthy people as

well. Although drinking water contaminated with human or an-

imal feces is the usual source of transmission of this organ-

Table 41.3.Foodborne Parasites, Fungi, and Viruses

Associated with Food- or Waterborne Illness

Pathogen Sources of Pathogen or Toxin

Parasites

Cryptosporidium Contaminated surface water or

foods in contact with

contaminated water

Cyclospora Raspberry, mesculun lettuce, and

basil

Sarcocystis Raw or undercooked meat

Toxoplasma Raw or undercooked meat

Giardia Contaminated surface water

Fungi

Penicillium Mycotoxins in apple juice, walnuts,

corn and cereals

Aspergillus Mycotoxins in groundnuts, corn,

figs and tree nuts

Fusarium Mycotoxins in cereals, corn, wheat

and barley

Viruses

Hepatitis A and E Contaminated water, fruits and

vegetables, raw shellfish, raw

oysters

Norwalk/Norwalk–

like viruses

Variety of foods and water

Calcivirus Water and contaminated foods

Astrovirus Water and contaminated foods

ism to humans, epidemiological links between the consump-

tion of contaminated foods such as raw sausage, offal, and

raw milk and cryptosporidiosis have been reported (Casemore

1990, Casemore et al. 1986). The largest outbreak of waterborne

cryptosporidiosis was reported in Milwaukee, Wisconsin, with

403,000 persons ill. Reported outbreaks in most countries are

associated with contaminated drinking water or contaminated

swimming pools.

Cyclosporais an emerging pathogen, which causes diarrheal

infections in humans. The first reported outbreak ofCyclospora

infection occurred in 20 US states and two provinces in Canada,

Ontario and Quebec, during the months of May and June, 1996,

and April and May, 1997. Consumption of contaminated im-

ported raspberries was implicated in many of these outbreaks

(Herwaldt and Ackers 1996, Herwaldt and Beach 1997). Con-

taminated mesclun lettuce and basil have also been linked to

Cyclosporaoutbreaks (MMWR 1997).

Sarcocystis is another coccidian parasite, which is prevalent

in livestock. Human infection occurs as a result of ingestion of

raw or undercooked meat containing mature sarcocysts (Tenter

1995).

Toxoplasma gondiiis an intracellular parasite, which is preva-

lent in man and animals (Fayer 1981). Ingestion of raw or un-

dercooked meat from livestock and game animals is often im-

plicated in human toxoplasmosis infections. Another parasite

commonly implicated in food and waterborne illness isGiardia.