Super Toxic Bug

Medscape Medical News, June 3, 2011

Be on alert for ‘Super Toxic’ Bug in Travelers, CDC says:

As health officials in Germany continued to seek the source of a uniquely toxic enterohemorrhagic Escherichia coli outbreak that has claimed the lives of at least 18 people, the Centre for Disease Control and Prevention issued a notice to healthcare providers to be on alert for the Shiga toxin producing E.coli O104:H4(STEC O104:H4) infections among travelers returning from Germany.

While there are some reports of the outbreak stabilizing the World Health Organization confirms that a total of 1823 cases of STEC O104:H4 have been reported, including 520 cases of hemolytic uremic syndrome, a potentially life threatening complication of the infection that can cause kidney failure. Twelve HUS cases were fatal and 6 deaths were reported among non-HUS cases.

The number of countries reporting cases of the STEC O 104:H4 poisoning had increased to 11 on Friday. However, all but 1 of the deaths since the outbreak emerged in May have occurred in Germany. The 18th death was reportedly in Sweden and involved a person who had recently returned from Germany.

Symptoms of the strain, which European authorities have called “super toxic”, are notably severe, including stomach cramps, bloody diarrhea, vomiting and fever. However, fever is not usually high.

Four suspected cases of the infection have been reported in United States, all involving people who had recently traveled to Hamburg, Germany, said Chris Braden MD, Director of Foodborne, Waterborne and Environmental Diseases for the CDC, at a press briefing today.

Three of the four cases in the US involved HUS and the patients were hospitalized. “The fourth case did not develop HUS but had bloody diarrhea, and we know there was a Shiga toxin producing organism involved,” he said.

Dr.Braden described the STEC O 104:H4 strain as “very rare” but not entirely unfamiliar.

“The CDC is not aware of any confirmed cases of this infection ever reported in the US. However, we have become aware of similar strains in other countries in the past,” he said.

The strain attacks the body in a manner unlike other strains of Shiga producing E.coli.

“The strain is different in its genetic markers and in the way it attaches to the lining of the intestine,” Dr. Braden added.

In addition to causing particularly severe symptoms, the strain is usual in that most of its victims appear to be women and people over the age of 20.

“It is true that in Germany 60% of the enterohemorrhagic E.coli cases and 71% of the HUS cases are female,” the WHO confirmed.

The unusual patterns underscore that little is known about the strain’s unusual nature, but they could also suggest the source that may be somehow related to the adult female demographic, Dr. Braden said.

“We have a lot to learn about this particular organism. It’s possible this organism had a predilection for adults over children, but it’s also possible the type of food or produce is being eaten by adult women than others.”

Dr. Braden also noted that the duration time from exposure to onset of symptoms is also unique, with incubation times of more than a week upto 12 days, compared to as little as 5 days commonly seen with other E.coli infections.

Most patients’ symptoms resolve within 5 to 7 days. However, HUS can develop a week after diarrhea begins. “The classic triad of findings in HUS is acute renal damage, microangiopathic hemolytic anemia( evidence of schistocytes and helmet cells on peripheral blood smear) and thrombocytopenia,” the CDC explained in a statement.

After backtracking on an earlier suggestion that the source of E.coli strain could be linked to organic Spanish cucumbers, German officials maintain that cucumbers, tomatoes and the lettuce are top suspects.

In addition, the Robert Koch Institute, Germany’s national disease control agency, has advised consumers, particularly those in the northern Germany region around Hamburg to avoid those vegetables.

In treating suspected STEC cases, some research has shown that administering antibiotics may in fact increase their risk of developing HUS, but the CDC recommended that clinicians ultimately determine treatment according to each individual patient. “There may be indications for antibiotics in patients with severe intestinal inflammation if perforation is of concern”, the agency said. “Of note, isolates of STEC O104:H4 from patients in Germany have demonstrated resistance to multiple antibiotics.”