Editor's Note: Hemolytic uremic syndrome (HUS) is the result of the simultaneous occurrence of microangiopathic hemolytic anemia, thrombocytopenia, and acute kidney injury. It is the most common cause of acute kidney injury in children, and over 90% of cases are the result of infection with Shiga toxin-producing Escherichia coli (STEC). Although the incidence in children younger than 5 years is reported at 2-3 per 100,000, that number has been increasing in recent years.
Recognizing enterohemorrhagic E coli (EHEC) as the likely cause of a presumed case of HUS is critical, because antibiotics and antimotility drugs should not be used in the management of these children. Medscape spoke with Prasad Bichu, MD, a pediatric nephrologist and Assistant Professor of Child Health at the University of Missouri Children's Hospital, about HUS, its epidemiology, and the recognition and management of these children.
Medscape: Can you address the rise in incidence of STEC HUS in recent years? What are some of the suspected reasons for the increase?
Dr. Bichu: Recent epidemiologic data from the US Centers for Disease Control and Prevention (CDC) estimate that STEC causes 265,000 illnesses, 3600 hospital stays, and 30 deaths each year. According to the CDC, most US cases of HUS have been the STEC O157 strain, but over the past couple of years, non-O157 STEC strains have caused HUS outbreaks.
It is unclear why the incidence of non-O157 STEC infections has increased. It seems logically intuitive that this may be due to increased consumption of raw food and unpasteurized milk in urban areas. There is a lot of misleading information online purporting that these products may be more nutritious and better for health. This information is potentially misleading and may be the underlying cause of the increased incidence of E coli, which then causes HUS. Exposure to water contaminated with animal waste is a common source of STEC infection in rural areas.
Medscape: We all know that EHEC is a foodborne pathogen, but what are the risk factors for infection with E coli O157:H7, the most virulent of the EHEC strains? Are there other factors that place children at particularly high risk?
Dr. Bichu: There are a number of factors that place kids at higher risk for exposure to O157:H7. I've already noted unpasteurized milk consumption, but kids can also be exposed via uncooked meat or contaminated food and water.
Exposure to undiagnosed children with STEC in the day care setting is another important risk factor. Sometimes the infected child does not appear to be ill. Other times, infection is missed and STEC is not diagnosed even if the child has been seen by a healthcare provider, as a result of unavailability of stool samples or the clinician not ordering the correct test.
My state has recently provided guidance to day care providers noting that children with EHEC must have at least 2 negative stool cultures before they should be allowed back into daycare. But if a kid has been having diarrhea due to E coli O157 and never been detected, he could still be spreading that infection to other kids in the daycare. Finally, there have been changes in the spectrum of the strain which causes STEC infection.
As far as the clinician is concerned, it's very difficult trying to differentiate between the strains of EHEC, because the symptoms are the same and, in actuality, it does not really make any difference in terms of management whether the organism is Shiga toxin-producing O157 or a non-Shiga-toxin-producing O157. It is more of epidemiologic value to know the strain as we try to evaluate how the spectrum of HUS and STEC E coli infections have progressed over the years, which may be important in understanding why HUS is becoming more common.
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Cite this: Hemolytic Uremic Syndrome: Why the Increase? - Medscape - Aug 28, 2014.