Among children with E. coli infections, those given antibiotics are more likely to develop a life-threatening complication called hemolytic uremic syndrome (HUS), according to a new study.

Avoiding antibiotics as a treatment for E. coli has been a longstanding recommendation for doctors; however this latest research – published Monday in Clinical Infectious Diseases – is the most comprehensive to date in that it takes into account the greatest number of cases and more than 200 different strains of E. coli O157:H7.

Researchers at Washington University Medical Center in St. Louis analyzed E. coli O157:H7 infections in 259 children over the course of 9.5 years. Cases studied came from 231 different strains of the bacterium, showing that the connection between antibiotics and HUS is not specific to certain strains in certain outbreaks.

The study also found two other risk factors that indicate a greater chance of developing HUS: vomiting and a high white blood cell count.  

However, “Antibiotics are the only thing you can really do anything about,” says Dr. Phillip Tarr, Co-Leader of the Pathobiology Research Unit and senior author of the study. 

And by “do anything,” he means do nothing when it comes to antibiotic treatment.

The study boils down to one simple message, he says: “Don’t give antibiotics.” 

Despite the fact that this is not new advice, it does not seem to be heeded by all physicians.

“Antibiotic use in these infections appears common,” notes the Washington University study.

Indeed a 2011 study from University of Colorado Denver found that out of 147 E. coli O157 patients, 62 percent were given antibiotics and 29 percent were prescribed these drugs even after stool tests confirmed their cases as E. coli infections. 

The authors of the Washington University paper cite another study, which found that between 2007 and 2008, 36 percent of HUS patients at 11 care centers in the U.S. and Scotland were given antimicrobials. 

A Minnesota study reported that these drugs were administered to 44 percent of participants (all children) infected with E. coli O157:H7.

 “It is very concerning that patients seeking care for diarrhea are more likely to receive antimicrobials than to submit their stools for culture,” note the authors of the Washington University study.

This study comes on the heels of a report which found that victims of the E. coli O104:H4 outbreak in Europe last spring were less likely to carry this bacteria long-term after being given the antibiotic azithromycin late in the course of illness. The findings from that study have given some researchers hope that that azithromycin may have value as a treatment for E. coli symptoms if administered earlier on. 

However in the Washington University study, “Azithromycin treatment did not confer benefit,” reports Tarr. Although he notes that the “numbers [of patients given this drug] were small.”