With back-to-back outbreaks of a potentially deadly strain of Escherichia coli -- one traced to California spinach in September and now another linked to products sold by Taco Bell -- some experts are renewing warnings against treating the symptoms with antibiotics.
For at least five years, the federal Centers for Disease Control and Prevention, the American Medical Assn. and other medical groups have advised against using antibiotics because of evidence that they can make patients sicker.
But some doctors still prescribe antibiotics because they are unaware of the advice, misdiagnose the still-rare E. coli O157:H7 or don't find the relationship between antibiotics and greater medical risk convincing.
The studies exist, "but I don't know how well known they are," said Dr. David Acheson, chief medical officer in the Food and Drug Administration's food safety center and one of several experts to warn against antibiotic use in treating the E. coli strain.
A 2000 study found that children infected by E. coli O157:H7 and given antibiotics developed a life-threatening complication called hemolytic uremic syndrome at higher rates than children who did not take antibiotics. The syndrome is the leading cause of kidney failure in children.
It is unclear whether antibiotics have contributed to the severity of the spinach- and Taco Bell-related outbreaks. A Riverside County couple believes, however, that the drugs endangered the life of their 7-year-old son, whose infection with E. coli O157:H7 may be linked to unpasteurized milk from a Fresno dairy.
When Tony and Mary Martin rushed their son, Sam, to a Riverside hospital in September, the first doctor they saw suspected E. coli and warned against using antibiotics to treat the boy's severe abdominal cramps and bloody diarrhea.
In the five days it took to get lab tests back on Sam's stool sample, the boy changed hospitals and physicians, and he was given the antibiotics Flagyl and Claforan.
Within hours, Tony Martin said, Sam's kidneys shut down. He spent two months in the hospital.
"This could have been prevented with a 3-cent band on his wrist that said, 'No antibiotics,' " Tony Martin said.
California and nine other states are taking part in a study by the CDC to help settle the antibiotic question. Preliminary results are expected by summer 2007.
"No one knows for sure whether antibiotics are a risk factor," said Dr. Linda Demma, a CDC epidemiologist. "Different doctors will do different things, since the literature is inconclusive so far. We're hoping to prove it one way or the other."
Scientists who have studied the link aren't waiting for further confirmation to preach restraint.
"It's kind of like aspirin and Reyes syndrome," said Dr. Phillip Tarr, professor of pediatric gastroenterology at Washington University in St. Louis and an author of the 2000 study. "No one ever did a control study that proved aspirin causes Reyes syndrome. But none of us will give aspirin for chicken pox."
Patients suspected of being infected with E. coli should be hospitalized and given intravenous hydration, he said.
The CDC discourages giving antibiotics for diarrhea in general because it promotes antibiotic resistance and because most people recover without treatment. Some doctors, however, prescribe antibiotics for a less dangerous Shigella bacteria because antibiotics reduce the amount of bacteria shed in stools and allow children to return to day care with less chance of infecting others.
E. coli O157:H7 is a nasty bug, apart from how it's affected by antibiotics. Like the toxin ricin, which causes similar symptoms when ingested, E. coli O157:H7 is on the nation's list of possible substances that could be used in bioterrorism attacks.
It is one of hundreds of strains of E. coli, usually a relatively harmless bacterium found in the intestinal tracts of cattle and other animals. The more potent strain first attracted notice in 1982, when 47 people became ill after eating undercooked fast-food hamburgers.
What sets this version apart from the more benign versions is its ability to produce potentially lethal toxins. The theory goes that as antibiotics attack the bacterium, the toxins begin replicating and burst into the body.
"When I was in academia," the FDA's Acheson said, "it was part of my mantra to talk about the dangers of antibiotic use."
Not everyone who takes antibiotics gets worse. And some develop hemolytic uremic syndrome without taking antibiotics. CDC scientists believe that the unusually high proportion of people in the spinach outbreak who were hospitalized or developed the syndrome was probably the result of a particularly lethal sub-type of E. coli O157:H7. They also think that the spinach may have been especially heavily contaminated with E. coli.
Two elderly women and a 2-year-old child died in the spinach outbreak last September, which sickened more than 200 people in 26 states.
As of Sunday, the CDC said, 61 people with illness associated with the Taco Bell outbreak, which might be linked to California-grown green onions, have been reported in five states.
The Martins believe that Sam contracted a strain of E. coli from raw milk. State health officials investigating four other cases of E. coli in September found that the only thing the sick children had in common was that they had drunk raw milk from Organic Pastures Dairy Co. Their investigation is ongoing.
The sub-strain of O157:H7 found in the children's stool samples was different from the spinach sub-strain.
Of the five children who drank raw milk and got sick, three who recovered fairly quickly were not treated with antibiotics. Sam and a girl from San Bernardino County were, and both developed hemolytic uremic syndrome.
The girl went home from the hospital in October, Sam in November. Most children with the syndrome recover completely, but Sam Martin will need to be monitored for long-term kidney damage and other complications.