TUESDAY, March 13 (HealthDay News) — Patients suffering from a
strain of E. coli that produces Shiga toxin, which can be deadly, appear
to respond to the antibiotic azithromycin (Zithromax), according to German
researchers.
Starting in May 2011, an outbreak of Shiga-toxin-producing E. coli
infected nearly 4,000 people in Germany, more than 800 of whom had
confirmed cases of hemolytic uremic syndrome (HUS), which causes red blood
cells to break apart, resulting in kidney failure.
Current treatment discourages using antibiotics for
Shiga-toxin-producing E. coli because it could increase the risk for HUS,
the researchers note.
“The successful decolonization of long-term carriers of the German
outbreak strain is an important finding, as the legal authorities in many
countries restrict long-term carriers in their social or working life,”
said lead researcher Dr. Johannes Knobloch, of the institute of medical
microbiology and hygiene at the University of Lubeck. “However,
decolonization by azithromycin should be investigated in further studies
for other E. coli strains.”
E. coli can cause persistent diarrhea, and it can be spread by those
infected through person-to-person contact.
The German outbreak was a mix of E. coli strains O157 and O104 (or
enteroaggregative E. coli), both investigated in the new study, which was
published in the March 14 issue of the Journal of the American Medical
Association. “For the treatment of one strain — enteroaggregative E.
coli — azithromycin is one of the antibiotics of choice,” Knobloch
said.
The study reports on 65 infected patients — some with HUS — who were
followed for almost 40 days after showing initial symptoms. Among these
patients, 22 were treated with azithromycin starting almost 12 days after
their symptoms began; the others were not.
Knobloch’s team found that there were significantly fewer carriers of
E. coli among those who took azithromycin, compared to those who
didn’t.
Twenty-one days after starting treatment, nearly 32 percent of those
taking azithromycin still carried the bacteria, compared with almost 84
percent of those not treated, they found.
After about one month, only 4.5 percent of those who received
azithromycin still had the bacteria, compared with more than 81 percent of
those who were not treated, and at 35 days none of the patients in the
treated group had the bacteria.
In addition, all the treated patients remained bacteria-free after two
weeks of antibiotic treatment, the researchers noted. However, 25 of the
43 untreated patients still carried the bacteria 42 days after their
symptoms started.
Based on the successful use of azithromycin, it was decided to provide
the drug to the 15 patients who still had symptoms.
After receiving azithromycin treatment, these patients no longer
carried the bacteria. Moreover, there were no signs of HUS among any of
the patients who took the antibiotic, the researchers said.
“This is a small study, but since other antibiotics activate the Shiga
toxin, this is a revealing study,” said Dr. Marc Siegel, an associate
professor of medicine at New York University in New York City.
“Azithromycin may well be the preferred antibiotic when you suspect an
aggressive E. coli or a toxic E. coli.”
Another expert, Hugh Pennington, emeritus professor of bacteriology at
the University of Aberdeen in Scotland, is more cautious.
This finding is “not surprising, but relevance to E. coli O157 is far
from certain,” he said. The O157 strain of E. coli is particularly severe
and also produces the Shiga toxin that often leads to hemolytic uremic
syndrome.
“Neither does it help much regarding the issue of antibiotic use
increasing the frequency of hemolytic uremic syndrome caused by E. coli
O157,” Pennington said. “The issue here, of course, is not whether
antibiotics help after hemolytic uremic syndrome has developed, but
whether they help to induce it. The jury is still out.”
More information
For more about E. coli, visit the U.S. National Library of Medicine.
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