[lit-ideas] Eat your spinach--or not

  • From: Robert Paul <rpaul@xxxxxxxx>
  • To: lit-ideas@xxxxxxxxxxxxx
  • Date: Fri, 20 Oct 2006 11:27:05 -0700

Forwarded by Robert Paul, Reed College.

A ProMED-mail post
ProMED-mail is a program of the
International Society for Infectious Diseases

Date: Fri, 20 Oct 2006
From: ProMED-mail <promed@xxxxxxxxxxxxxx>
Source: San Francisco Chronicle [edited]

[1]2006's lethal outbreak of _E. coli_ in fresh spinach from the Salinas
Valley was caused by a particularly malevolent breed of the bacteria that
had previously sickened 109 Americans in 31 states, according to federal

Scientists have been tracking outbreaks of _E. coli_ O157:H7 since it
appeared in undercooked hamburger in 1982. Within this dangerous microbial
family, however, scientists have since recorded the genetic fingerprints of
20 000 subtypes. All of the victims in the spinach outbreak this summer
were sickened by a single subtype labeled EXHX01.0124. It may be the most
dangerous strain of O157:H7 yet detected.

"This bacterium is clearly more virulent than those in other outbreaks,"
said Kevin Reilly, deputy director for prevention services at the
California Department of Health Services. Half of those made ill by the
bacteria were hospitalized, kidney failure rates in children were more than
triple the norm, and 3 people have died.

Disease detectives first booked No. 0124 into the CDC's genetic fingerprint
computer in Atlanta in December 1998, when it turned up in 3 cases in
Massachusetts. It popped up again in 2000, causing a single illness in Kansas.

Then the rap sheet for 0124 began to grow -- from 5 states in 2001 to 37
states in 2005. Before a single case of spinach-related illness was logged
in 2006, there were already 34 cases in 17 states -- all of them caused by
the same rogue strain.

It is unlikely that scientists will ever discover how the 0124 strain
arrived in the Salinas Valley, but the record shows in retrospect that it
had been silently spreading throughout the country for at least 8 years.

The 0124 subtype accounts for less than 1 percent of the strains reported
each year, but it has been increasingly prevalent, said Dr. Peter
Gerner-Smidt, who tracks the subtypes of _E. coli_ at the CDC as chief of a
unique surveillance program known as PulseNet. Until the spinach outbreak,
it did not draw enough attention to bring on a more serious analysis. "It's
not a very common strain," Gerner-Smidt said.

Each year, laboratories in state health departments throughout the country
log several thousand cases of _E. coli_ infection, and submit the genetic
fingerprints of each case to PulseNet via a secure Internet line. There are
73 000 cases of _E. coli_ O157:H7 food poisoning each year, but seldom do
they appear in clusters large enough to trigger closer scrutiny. So
scientists never traced how the 109 victims were infected by the 0124 strain.

That changed in late August 2006, when Wisconsin health officials noticed a
spike in _E. coli_ cases. More worrisome, the severity of the illness was
unusual. When the DNA fingerprints of the bacteria were taken, they were a
match for 0124. When the state of Washington reported the same strain in
another cluster of patients, federal officials knew they had a large
multistate outbreak on their hands.

Gerner-Smidt agrees that that 0124 is probably a more dangerous strain than
others. Research is under way to figure out why.

Typically, _E. coli_ O157:H7 causes severe cramping and bloody diarrhea,
and about 10 percent of children who get it develop a life-threatening
kidney damage called hemolytic uremic syndrome. Of the 199 confirmed cases
in the spinach outbreak, however, 39 percent of children afflicted
developed the kidney condition, as have about 10 percent of adults. "That
is highly unusual," said Gerner-Smidt.

One possible explanation for 0124's unusual punch lies in its molecular
makeup. All _E. coli_ O157:H7 strains are dangerous because they are armed
with toxins similar to those found in the intestinal disease shigellosis.
Most strains carry 2 kinds, known as Shiga Toxin Types 1 and 2. But the
spinach outbreak strain appears to carry only Type 2.  Early research on
_E. coli_ suggests that Type 2 toxins are more potent than Type 1, and that
strains that carry Type 2 alone are more dangerous than those that carry
only Type 1 or both.

The unusual severity of illness found in the spinach outbreak is consistent
with those laboratory findings. Research is also under way to determine if
there is anything about the 0124 subtype that makes it more likely to grow
on spinach or other leafy green vegetables. UC Davis plant scientist Trevor
Suslow said that many strains of _E. coli_ O157:H7 have been tested on
lettuce and other leafy greens, and so far there is no evidence that any of
them grow better than others in plants. But Suslow said the hunt is on to
find out just how common this unwanted and dangerous intruder has become in
America's salad bowl.

In 8 of 9 years prior to this summer's outbreak of a particularly virulent
strain of _E. coli_ O157:H7 among consumers of fresh spinach, the CDC had
detected the same microbe in 109 patients scattered through 31
states.  Annual cases caused by same genetic subtype of _E. coli_
responsible for the spinach outbreak:
1998: 3
2000: 1
2001: 6
2002: 12
2003: 8
2004: 8
2005: 37
2006: 233 (199 Since August outbreak)


From: ProMED-mail <promed@xxxxxxxxxxxxxx>
Source: CBS2 Chicago [edited]

Two new cases of illness from the _E. coli_ bacterium linked to spinach
have been reported in Illinois.  The state Health Department said the 2
newest cases involve a woman from downstate Illinois and a child from the
northeast part of the state. It was not specified where in northeast
Illinois the child lived.  So far in Illinois, 4 cases of _E. coli_-related
illness have been linked to the national outbreak.

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