Microbial Hazards in Foods: Food-Borne Infections and Intoxications 495Kalamaki, Price, and Fung (1997) sum-
marized screening and identifi cation test kits
for Escherichia coli in Table 1 of their article.
Similar tables for the detection of Entero-
bacteriaceae, Campylobacter, Salmonella,
Listeria, Rotavirus, Staphylococcus aureus,
Vibrio cholerae, and V. vulnifi cus are pre-
sented in the same publication. Due to these
developments, it is possible now to have a
negative screening of Escherichia coli
0157 : H7 in about one day. However, when
a food sample shows a positive screening
result, the conventional methods must be
used to confi rm the presence or absence of
E. coli 0157 : H7.
From a food industry point of view, E. coli
O157 : H7 has an even more important role in
food safety and commerce because in 1994,
this was the only microbe to be declared a
“ food adulterant ” by offi cials of the U.S.
government. This implies that if E. coli
O157 : H7 is found in a batch of ground beef,
the producer has violated the law. Thus, mil-
lions of pounds of ground beef have been
recalled and destroyed in the past several
years because of this ruling in the United
States.Yersinia enterocolitica
Yersinia enterocolitica is a Gram - negative,
facultative anaerobic, non - spore - forming
bacterium; it is sucrose - positive, rhamnose -
negative, indole - positive, motile at 20 ° C but
not at 37 ° C, and highly virulent to mice.
Serotyping is very important in separating
this organism from other closely related
Gram - negative bacteria. Although Y. entero-
colitica has an optimal growth temperature at
around 32 ° to 34 ° C, it is often isolated on
enteric agars at 22 ° to 25 ° C. It grows slowly
in simple glucose - salts medium but grows
much better with supplements such as methi-
onine or cysteine and thiamine. One impor-
tant aspect of this organism is that it can
grow in refrigerated vacuum - packaged meat
because it is a facultative anaerobe and is aThis method is now used extensively for
large - scale detection of E. coli O157 : H7 and
other pathogens. This organism will continue
to be very important in food microbiology for
the foreseeable future.
ETEC or enterotoxigenic E. coli are the
major causes of infantile diarrhea in develop-
ing countries and are most frequently respon-
sible for traveler ’ s diarrhea. The serotypes
involved include O8, O15, O20, O25, and
others.
EIEC or enteroinvasive E. coli are strains
that cause nonbloody diarrhea and dysentery
by invading and multiplying within colonic
epithelial cells. Serotypes include O28ac,
O112, O124, and others.
EAggEC — enteroaggregative E. coli —
cells affect infants and children with persis-
tent diarrhea. They have the characteristic
pattern of aggregative adherence on Hep - 2
cells.
EPEC or enterotoxigenic E. coli has been
defi ned as “ diarrheagenic E. coli, belonging
to serogroups epidemiologically incrimi-
nated as pathogens but whose pathogenic
mechanisms have not been proven to be
related to heat - liable enterotoxins (LT), heat -
stable enterotoxins (ST), or to Shigella - like
invasiveness. The serotypes included in
EPEC are O55, O86, O111ab, O119, O125ac,
o126, and others.
DAEC or diffusely adherent E. coli have
been associated with diarrhea in children in
Mexico and can produce mild diarrhea
without blood or fecal leukocytes.
A comprehensive treatment of E. coli
O157 : H7 and other E. coli strains, as well as
many food - borne pathogens, can be found in
the book by Doyle, Beuchat, and Montville
(1997).
Prevention and control of pathogenic E.
coli is best done by educating food - handlers,
who should adhere to strict hygienic prac-
tices. Fecal and other waste materials from
humans and animals should be decontami-
nated and not allowed to be in contact with
water and food supplies.