Modernist-Cuisine-Vol.-1-Small

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A Bestiary of Foodborne Pathogens
The foodborne pathogens that are known to science come in a wide array
of shapes and sizes, and they vary wildly in their behavior and virulence.
The six groups that pose the greatest concern to cooks are listed below
from largest to smallest. Each has different risks, but the means of
addressing the risks vary in each case. Although plasmids—infectious
strands of DNA—can exist within a range of organisms, we discuss them
in the context of their bacterial hosts, in which they play critical roles in
causing disease.
Parasitic worms (see page 120)
Parasitic worms are the largest of the foodborne
pathogens. They can live for decades and grow
to dimensions that are clearly visible to the
naked eye.
Size: they range from microscopic worms a tiny
fraction of a millimeter long to tapeworms that
can reach 9 m / 30 ft in extreme cases
Associated illnesses: trichinellosis, anisakiasis,
ascariasis, fascioliasis, “fish flu,” and taeniasis
Examples: roundworms such as Trichinella
spiralis (above top and bottom), Anisakis simplex,
and Ascaris lumbricoides;
flukes such as Fasciola hepatica and
Nanophyetus salmincola;
tapeworms such as Taenia saginata and
Taenia solium
Protists (see page 126)
This incredibly diverse group of mostly singlecelled
microorganisms includes fungus-like,
plant-like, and animal-like varieties. Most
animal-like protists (or protozoa) are harmless,
but a few parasitic species can be deadly,
including Toxoplasma species.
Size: typically 0.005–3 mm, although brown
algae can range from 0.001 mm to 100 m / 328 ft
Associated illnesses: toxoplasmosis, giardiasis
(“beaver fever”), cyclosporiasis (“traveler’s
diarrhea”), and amebiasis
Examples: Toxoplasma gondii (above top)
Giardia lamblia (above bottom)
Cyclospora cayetanensis
Cryptosporidium parvum
Entamoeba histolytica
Bacteria (see page 130)
Bacteria are perhaps the most famous form of
single-celled life; they are diverse, hardy, and
highly adaptive. Bacteria can cause foodborne
illnesses in more ways than any other pathogen
because they can multiply on food before
consumption.
Size: although the typical range is 0.001–
0.005 mm, these microorganisms have diameters
that run from 200 nanometers (200
billionths of a meter) to 700 microns (700
millionths of a meter, or 0.7 mm)
Associated illnesses: salmonellosis, shigellosis,
listeriosis, and other bacterial infections such as
those caused by Escherichia coli strain O157:H7
and Campylobacter species; also multiple forms
of food poisoning such as botulism
Examples: E. coli (above top)
Campylobacter jejuni
Listeria monocytogenes
Yersinia enterocolitica
multiple Salmonella species
multiple Shigella species
Clostridium perfringens (above bottom)
Staphylococcus aureus
Bacillus cereus
Viruses (see page 152)
Because viruses have genes that are composed
of DNA or RNA, these microorganisms can
evolve like other life forms. Yet most scientists
do not consider them fully alive because they
cannot grow or reproduce beyond the confines
of the cells they infect. A single group, the
noroviruses, causes two-thirds of all known
foodborne illnesses in the United States.
Size: 20–400 nanometers (billionths of a meter)
Associated illnesses: norovirus-, rotavirus-, or
astrovirus-linked gastroenteritis, and foodborne
hepatitis
Examples: norovirus (above top)
rotavirus (above bottom)
hepatitis A virus
astroviruses
Plasmids (see page 133)
Plasmids are naked strands of DNA that supplement
a microbe’s normal set of genes. Multiple
and identical copies of a plasmid can exist
within the same cell, and in bacteria those DNA
strands often move from one cell to another,
sometimes converting the recipient into
a potent killer.
Size: The plasmids that reside in bacteria can
contain from 1,000 to more than 1.6 million base
pairs, or “letters,” of DNA. If a plasmid’s genetic
strand were stretched out from end to end, its
length could exceed that of the host organism.
Plasmid DNA is normally tightly coiled, however,
so that many copies can fit easily inside
a cell.
Associated illnesses: shigellosis, E. coli O157:H7
infection, and many other diseases related to
foodborne bacteria
Examples: the pINV plasmid that is required for
invasive E. coli and Shigella bacterial strains to
function;
the p0157 plasmid within E. coli O157:H7;
the pSS plasmid of Shigella sonnei;
plasmids associated with Yersinia enterocolitica,
Clostridium perfringens, and other diseasecausing
bacteria
Prions (see page 156)
Prions are the simplest pathogens yet discovered;
they are infectious proteins that can
change normal bodily proteins into misshapen
versions that create disease. These “good
proteins gone bad” can cause rare foodborne
illnesses that eventually prove fatal.
Size: Scientists estimate that a human prion is
4–5 nanometers (billionths of a meter) in
diameter
Associated illnesses: kuru (above top) and
variant Creutzfeldt-Jakob disease (above
bottom); researchers have linked kuru to bovine
spongiform encephalopathy (BSE), known
informally as “mad cow disease”
Examples: a prion is often referred to by
biochemists as either a prion protein cellular,
or PrP C , when it is normal, or as a prion protein
scrapie, or PrP Sc , when it is abnormally folded
and therefore capable of causing disease
(scrapie is a disease of sheep that is similar
to BSE)
108 VOLUME 1 · HISTORY AND FUNDAMENTALS
MICROBIOLOGY FOR COOKS 109