What the Heck is an E. coli ?
What's going on, here?
Here we go again --- This "bug" simply refuses to disappear from
the news. Every time you turn around anymore, there are warnings about
hamburger meat (involving Hudson Foods and E. coli, or
non-pasteurized apple juice and E. coli.
So, I thought it might be useful to find out
just what an "E. coli" is, and why all the warnings. Before we
start with the problems, it'll help to discuss some background, first.
What does E.coli mean?
E. coli is the abbreviated name of the bacterium in the Family
Enterobacteriaceae named Escherichia (Genus) coli
(Species). Dave Graham in the Department of Microbiology, University
of Illinois at Urbana/Champaign, recently pointed me to information
gleaned from G.W. Tannock's book, Normal Microflora,1995, Chapman & Hall,
which reveals that approximately 0.1% of the total bacteria within an
adult's intestines (on a Western diet) is represented by E. coli.
Although, in a newborn infant's intestines E. coli, along with
lactobacilli and enterococci represent the most abundant bacterial flora.
In fact, it is for this reason that the organisms which happily inhabit
the intestinal tract as normal flora are named enteric bacteria. The
Family to which E. coli belongs (Enterobacteriaceae, is
named what it is - because of the Greek word enterikos - which
pertains to the intestine. The name Escherichia comes from the
name of the person Escherich, who in 1885 first isolated and
characterized this bacterium.
I thought E.coli bacteria were OK....
You are correct, for the most part. The presence of E. coli and
other kinds of bacteria within our intestines is necessary for us to
develop and operate properly, and for us to remain healthy - E.
coli, along with other species of bacteria, provide us with many
necessary vitamins for example. The bacteria make the vitamins, and we
gladly absorb them. We pretty much depend upon E. coli in our
intestines for our source of Vitamin K and B-complex vitamins.
The fetus of any animal is completely sterile. Immediately after birth
however, the newborn acquires all kinds of different bacteria which live
symbiotically (we help them to live, and they help us to live) with the
newborn and throughout the individual's life. From the day we are born,
we are _never_ without bacteria. However, the helpful bacteria like
these are located "only" in regions of our body directly
exposed to the environment, e.g., our intestines, upper and lower respiratory
tract, etc... and never within our bloodstream or the tissues inside our
body. Sounds weird, but, it's true - billions of these little critters
chugging away, making things we need, helping to digest our food, etc.,
-- very important to us and most of them are exceedingly kind to us - except
when they become teenagers and enter the throes of puberty (just kidding).
Indeed, animals who are born and raised "germ free", are really
wimpy.... they have thin intestinal walls, puny heart output, and require
lots of vitamin supplements just to stay alive.
So, when are E.coli bacteria bad for us?
Truly, you have billions of "friends" that you never knew you
had. So, "What's the big deal about E. coli?" you ask with a
puzzled expression on your face. Well, now I need to talk about the
"bad guys." Bacteria are somewhat like humans in that certain
individual humans are not very nice - and we know that some individual humans
can be downright dangerous. Of course _all_ humans belong to the Genus/Species
Homo sapiens, and all E. coli belong to, well, Escherichia
coli. So, as there exist individual humans, so too can different individuals
exist among E. coli bacteria - we call such individuals a different
"strain" of bacteria within a given species. Some of these
different strains of bacteria (there may be several within a given
species) can be harmful to us. Each of us - given the assumption that a
human is reading this information - is sort of a strain of the human
species, sapiens. We are different because we are genetically
different, e.g., unless we are one member of an identical twin pair, the
combination of genes each of us possess is different from every other
human on the face of the earth - or arm of the earth for that matter. If
you think about it a little bit, there are only about 5-billion (is that
about right?) humans who are alive on the earth - there are probably that
many bacteria in your intestine alone - don't worry - they don't take up
much room.... So, it is possible for us to acquire an individual strain
of E. coli which mixes with the other E. coli in our
intestines. Now, since an individual strain of E. coli may exist,
this situation means that this particular strain of E. coli is
genetically different than the vast majority of E. coli in our
intestines; otherwise, it would not be a different strain of this
organism. If this E. coli strain happens to have genetic
information for producing something harmful to us, then, we may be in
OK; who "is" the bad guy?
The rare strain of E. coli that is getting a lot of
"press" lately because it is indeed a bad bug, is E.
coli O157:H7, a member of the EHEC - enterohemorrhagic E.
coli group. Enterohemorrhagic means an intestinally-related (here we
are at the Greek word enterikos again) organism which causes
hemorrhaging - and therefore, loss of blood. The image shown below
is a picture of an electron microscope visualization (an electron
micrograph) of O157:H7 (compliments of David Graham, University of
Illinois at Urbana/Champaign).
How then do we "pick up" this organism?
Basically, here is the problem: E.coli bacteria are everywhere
in the environment. But, since they are such a common occupant of all animals,
anytime we eat something, drink something, or touch our hands to something
that has been either a part of or has been near where animals are, there is
always the potential to ingest these bacteria - is a good reason for washing
your hands now and then, huh?
How did this strain of E. coli come to be?
Since bacterial cells are all over the place, it is possible for them to
acquire genetic information from other sources (bacterial viruses,
plasmids, or just naked pieces of DNA floating around and about) - bacteria
are "pretty good" at this - this information has nothing to do with
the original genetic information necessary for the survival of the bacterium -
although in some cases, acquisition of this information may provide an
advantage for survival. In the case of E.coli O157:H7, a long-ago
cell appears to have been infected with a bacterial virus. This particular
virus had the ability to insert its own DNA into the bacteria's chromosome
without harming the bacterium - and to remain there. Now, every time this
bacterial cell divided, the virus DNA, being now a part of the bacterial DNA,
was passed on to every daughter cell - and now, we have the E.coli
strain, O157:H7.... This virus's genetic information (genes) unfortunately
(for us) contained information for the production of a toxin, called Shiga-like
toxin (SLT), or is sometimes called, Vero toxin. Consequently, this strain of
E.coli, and all of its progeny produce this toxin. The toxin is a
protein which causes severe damage to intestinal epithelial cells (the cells
that line the wall of the intestine). The damage is so severe that if we
acquire this bacterial strain, not only do we lose water and salts, blood
vessels are damaged, and bleeding occurs - lots of bleeding - hemorrhaging.
This condition is particularly dangerous to small children - may be lethal -
children are too small to tolerate much blood and fluid loss. It is for this
reason that small children should not be allowed to become dehydrated, even in
mild cases of diarrhea. Too, in some cases another syndrome is involved which
is called hemolytic uremic syndrome (HUS), which is characterized by kidney
failure and loss of red blood cells. Approximately 5% to 10% of little kids
progress to this stage of disease - which is very dangerous for them. In
severe cases, the disease can cause permanent kidney damage. The presence of
this bacterium can also be very dangerous to the elderly or infirm. There can
be a combination of HUS and some other things which involve the blood system,
which can be lethal to the elderly in 50% of the cases. So,
E.coli O157:H7 is a dangerous organism, for sure.
1. As of August, 1997, various "lots" of hamburger meat
produced for shipment by Hudson Foods were found to be contaminated with a
harmful strain of E. coli. The strain of E. coli involved
is again O157:H7. The Hudson Foods plant in Nebraska responsible for
the contaminated beef is now closed. Approximately 25 million pounds of
beef are being recalled - all of the beef shipped from this
plant. And, all beef presently at the plant is being destroyed. If you
wish, please examine the following link to information regarding recalls.
U S Food & Drug
Administration Center for Food Safety & Applied Nutrition.
Interestingly, the USDA as no authority to force an industry to recall
food which threatens the safety of the population in the US. The
government can only recommend that the meat be recalled. The
Secretary of Agriculture states that he is planning to see that Congress
again consider legislation to increase the authority of the USDA - the
arm of the Federal Government which is responsible for the safety of food
products in the nation.
During and after November, 1996, I am sure that you heard about the
outbreak of O157:H7 E. coli in Canada, the Northwest and West (US).
The outbreak has been traced to ingestion of a popular brand of non-pasteurized
apple juice (Odwalla, Inc.). I believe that one 16 month-old child has
died in Colorado as a result of the illness caused by this bacterium, and a
fairly large number of people were made severely ill (40) in British
Columbia, California, Colorado, and Washington. This brand of apple
juice is distributed to: Washington, California, Oregon, Colorado, New
Mexico, Nevada, Texas, Idaho, and British Columbia. As of November 12,
1996, there is a call for legislation which will require that all apple juice
be pasteurized - just as milk is required to be pasteurized. Louis Pasteur
developed a process whereby milk is treated with heat (63C for 30 minute -
older method) to kill harmful bacteria (will not kill spores), but
nowadays milk and other pasteurized products produced in large quantities are
often treated by a modification of the older method. This process, called
flash pasteurization, involves exposure of milk and other liquid products to
at least 72C (approx. 162F) for at least 15 seconds, with rapid cooling.
Please see: Better Use a Pressure Cooker!
for more information on the use of heat to kill harmful organisms.
As of July 23, 1996, there had been about 8,000 cases of an EHEC strain
affecting people in a city in Japan. According to an email contact from Mr.
John Harrington in Osaka, who wrote: "The Ashahi Evening Newspaper
(Wed., July 24 edition), [states that as of] Tuesday, 8444 people throughout
Japan have developed O157-like symptoms. More than 6000 of them are in
Sakai, a suburb of Osaka. The outbreak has now spread to 40 of 47
prefectures (the equivalent of US counties), and the number of victims
seems to increase steadily at about 100 [per] day. Most recently, a 10
year old girl and a 85 year old woman died." From news reports it is my
understanding that over 600 children have become infected, and almost 60 of
them are in critical condition - with the uremic syndrome mentioned above. So
far, the authorities cannot locate the source of the contamination - school
lunches, they think. Unfortunately, when the outbreak among school children
in Sakai initially occurred, the remaining lunches were destroyed - so - there
are no samples from which to try to isolate the organism (locate the source of
contamination). I do not know if this strain is O157:H7 - there are several
different verotoxin-like expressing strains of E. coli, several of
which have been identified in Japan... each numbered in a similar fashion.
Hopefully, the Japanese health workers will be able to locate the source of
the problem, and the children will be OK.
What does all of this information have to do with hamburger meat,
or other food products?
We'll talk about meat products first. Unless there is a cut in the meat,
the meat below the surface is normally sterile (unless there is some
intracellular organism present). However, whether or not some intracellular
bug is around, the outside surfaces of all meat will have bacteria present -
so - if some meat happens to be contaminated with the rare E.coli strain,
O157:H7, it will be on the surface of the meat, and not down inside the fibers
of the meat. However, as soon as the meat is cut with a knife or punctured
with a fork, the knife blade or fork tine will carry the bacterial cells down
into the cut or puncture - usually, such a situation is relatively safe
because we cook the meat - certainly we cook the surface of the meat.
Remember though, bacteria are _really_ small, so even a tiny, pretty much
invisible cut in the meat could introduce bacteria down inside. In the case of
E.coli O157:H7, the total number of bacteria required for
infection appears to be about 10 - that's
right, only 10 bacterial cells! Therefore, it is always safest to
cook _all_ meat at least until the juices of the meat run absolutely
clear - not pink - clear.
Now, if the meat is ground (we call it hamburger if it's ground
beef) we have a much more risky situation because any bacterial cells
originally only on the surface of the meat, will _now_ be distributed
_throughout_ the preparation. It is _very_ important in this case to
thoroughly cook the meat - until the juices run absolutely clear.
Actually, the latest recommendation is that each hamburger
pattie must reach an internal temperature of 160 degrees F.
Apparently, viable (living) E. coli have been isolated from
hamburger meat cooked to the point of "juices running
clear". This procedure is very similar to that one would use to
cook pork or perhaps a Thanksgiving turkey, e.g., observe the internal
temperature of the meat before it is served.
Just remember, if you like your meat and especially hamburgers,
"rare", you are taking a significant risk. It is also
important to realize that meat may not be the only source of
contamination with such bacteria or other dangerous bacteria - any
contaminated water source or contaminated person can load these bacteria
onto vegetables, etc. So, it is a good idea to be careful with
everything - wash fresh fruit, vegetables, etc., thoroughly before
eating. This last statement is very important, since as mentioned above,
recent cases of O157:H7 infection have been found associated with
non-pasteurized apple juice. This organism is apparently
spreading around and about. So, it is important to be vigilant and aware.
What do I do if I or someone in my family gets sick after eating
hamburger or something else - or for that matter, just gets sick?
No matter when, - if diarrhea occurs, always pay close attention
to the symptoms... look for the presence of fever, vomiting, etc.,
particularly if the person is an infant, a small child, or an elderly or
infirm adult. Look for any signs of blood in the stool. If you see
anything that worries you, call your physician immediately - don't
worry about the possibility of being mistaken and perhaps looking "silly."
The organism is difficult to identify [recommended method is to use a genetic
probe - associates with the toxin's(s) gene sequence(s)] - so - be as patient
as possible - treatment will be given for the symptoms and treatment will be
given to help rid the person of the infection.
How long does it take for any symptoms to appear?
Well, the answer to this question is a tough one. There are many things
which may influence the onset of symptoms for this particular disease.
Symptoms may appear within hours or may appear only after several
days. It is for this reason that if diarrhea occurs, one should
examine the stool for blood, and pay attention to any other symptoms
which may occur, particularly if the person affected is a young
child, is elderly, or is infirm in any way. The following are some of the
things which can influence the time it takes for symptoms to occur:
(1) The actual number of organisms ingested - the higher the number
ingested, the sooner the possibility for symptoms (the relatively greater
concentration of toxin made).
(2) The health status of the individual - the weaker or less healthy,
the sooner the possibility for symptoms.
(3) The individual's natural resistance to either (a) the
growth of the organism within the intestine, or (b) the effect of the
toxin itself. Different people may respond differently.
Usually, the disease is self-resolving (means that the disease clears
"on its own") within about 8 days or so. However, as stated above,
if any blood appears in the stool, or if watery diarrhea appears
in an infant or a small child, one should immediately contact
one's physician and describe the symptoms as accurately as possible.
Whether or not E. coli O157:H7 is involved, diarrhea for any
reason in a little kid can potentially be dangerous - so - discuss the symptoms
with your physician if you are the least bit concerned.
How can I reduce the risk of infection from E.coli O157:H7?
The best advice is to of course be smart about all of this... realize
that there is always a risk and simply take common-sense actions to
minimize the risk.
- Always clean any surface that has come in contact with raw
meat, before any other item is placed on that surface.
- Always thoroughly wash your hands after handling raw meat, and
before you handle any other utensils or other food items.
- Never use the same plate, tray or utensils for the cooked meat
that you use for the raw meat - unless you thoroughly wash the plate, tray or utensils
- Always cook meat, _especially_ ground meat, until the juices
run absolutely clear - pink _is not_ good enough. In fact, it is
necessary for the internal temperature of a hamburger pattie to reach 160
degrees F to kill all of any contaminating E. coli.
- In day-care centers, schools, etc., any small children with diarrhea
should be carefully handled, and kept separate from all well children. All
diapers, and any soiled clothing should be kept separate from all well
children. The day-care worker, teacher, and health-care personnel should
practice strict hygeine at all times, regardless of the health of the children.
Here is a link to the
National Food Safety Database with all kinds of useful information
about Food Safety. And, here are links to other pages with information on
E. coli O157:H7, and other emerging strains of enterohemorrhagic
E. coli. Please see:
All About Beef
from the USDA;
"The Bad Bug Book" provided by the FDA; and,
on Hemolytic Uremic Syndrome in South Australia, and a link to the
Centers for Disease Control and Prevention (CDC), Atlanta, Georgia:
Centers for Disease Control.
Copyright John C. Brown, 1995, updated September 16, 1997.
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