E. Coli O26 Data Point to a "Low-Virulence Pathogen"

CHICAGO – Escherichia coli O26 does not appear to cause severe disease in children, according to an epidemiologic study of a recent outbreak in an Oregon child care center.

In all, 60% of 10 infected children and staff were asymptomatic, and none developed illness more serious than diarrhea, investigators reported at the annual Interscience Conference on Antimicrobial Agents and Chemotherapy.

Shedding in the stool of infected children was prolonged, lasting up to 46 days, but there was no secondary transmission of the pathogen to household members.

Laboratory testing showed that the pathogen produced type 1 Shiga toxin but not type 2 Shiga toxin, which is seen in some other E. coli serotypes and carries a higher risk of hemolytic uremic syndrome.

In all, 60% of 10 infected children and staff were asymptomatic, and none developed illness more serious than diarrhea, investigators reported

"This study raised more questions than it answered," acknowledged lead investigator Dr. Mathieu Tourdjman, a Centers for Disease Control and Prevention Epidemic Intelligence Service officer with the Oregon Health Authority in Portland. But taken together, the findings generally point to a low-virulence pathogen.

This new information does not warrant any change to Oregon’s policy for child care settings when O26 is detected, according to Dr. Tourdjman. That policy requires that infected children be excluded until they have two consecutive negative stool samples, but allows the local health department to waive the exclusion at its discretion.

"In the context of an O26 Shiga toxin 1–only outbreak in a child care center, we continue to recommend that symptomatic children be excluded at least until symptoms resolve, and that the incidence of infection should be closely monitored," he said. "Routine hand washing before meals and before and after changing diapers and toileting should be emphasized."

And restriction criteria should remain flexible. "In the absence of severe disease, requiring two consecutive negative stool samples to lift the exclusion might not be justifiable," Dr. Tourdjman commented. "And routine testing of asymptomatic children should not be recommended."

Public health officials agree that children with E. coli O157 (the most common serotype) should be excluded from child care until two consecutive negative stool samples are obtained, he noted by way of background. But because of a lack of data, there is no consensus when it comes to restrictions for children with E. coli O26, the second most common serotype.

The Oregon outbreak occurred in October 2010 at a child care center having 76 attendees aged 6 weeks to 12 years, Dr. Tourdjman reported at the conference, which was sponsored by the American Society for Microbiology.

Overall, 61 people – all 13 staff, all 41 attendees in four of five preschool classrooms, and all 7 school-aged siblings of those attendees – provided stool samples for testing.

Results showed that nine of the children and one of the staff were positive for Shiga toxin–producing E. coli O26, as determined by initial polymerase chain reaction for the toxin and confirmed by subsequent stool culture for typing.

Four of the 10 positive individuals, all children, had diarrhea, which was bloody in one case. But none experienced hemolytic uremic syndrome or other serious illness. Laboratory tests showed that all isolates matched and all produced only Shiga toxin type 1.

Of the nine infected children, two had consistently negative test results after their initial positive result. Among the other seven, the median duration of shedding in stool was 25 days, with a maximum of 46 days.

Half of the households of infected children agreed to testing to assess possible secondary transmission, and 14 of 17 household members provided stool samples. None were positive by polymerase chain reaction for Shiga toxin.

In the wake of the outbreak, the child care center was thoroughly cleaned and staff were trained in hygiene practices, according to Dr. Tourdjman. The children with diarrhea were excluded from the center, and the asymptomatic positive children were cohorted (separated from other children in a single classroom).

However, the cohorting was discontinued after 3 weeks given that all factors pointed to a low-virulence pathogen and there was strict compliance with the hygiene practices. "The decision to stop cohorting was not based on the results of the shedding study," he noted. "No symptoms were reported at the center after the discontinuation of cohorting."

Dr. Tourdjman did not report any relevant financial conflicts of interests.

CHICAGO – Escherichia coli O26 does not appear to cause severe disease in children, according to an epidemiologic study of a recent outbreak in an Oregon child care center.

In all, 60% of 10 infected children and staff were asymptomatic, and none developed illness more serious than diarrhea, investigators reported at the annual Interscience Conference on Antimicrobial Agents and Chemotherapy.

Shedding in the stool of infected children was prolonged, lasting up to 46 days, but there was no secondary transmission of the pathogen to household members.

Laboratory testing showed that the pathogen produced type 1 Shiga toxin but not type 2 Shiga toxin, which is seen in some other E. coli serotypes and carries a higher risk of hemolytic uremic syndrome.

In all, 60% of 10 infected children and staff were asymptomatic, and none developed illness more serious than diarrhea, investigators reported

"This study raised more questions than it answered," acknowledged lead investigator Dr. Mathieu Tourdjman, a Centers for Disease Control and Prevention Epidemic Intelligence Service officer with the Oregon Health Authority in Portland. But taken together, the findings generally point to a low-virulence pathogen.

This new information does not warrant any change to Oregon’s policy for child care settings when O26 is detected, according to Dr. Tourdjman. That policy requires that infected children be excluded until they have two consecutive negative stool samples, but allows the local health department to waive the exclusion at its discretion.

"In the context of an O26 Shiga toxin 1–only outbreak in a child care center, we continue to recommend that symptomatic children be excluded at least until symptoms resolve, and that the incidence of infection should be closely monitored," he said. "Routine hand washing before meals and before and after changing diapers and toileting should be emphasized."

And restriction criteria should remain flexible. "In the absence of severe disease, requiring two consecutive negative stool samples to lift the exclusion might not be justifiable," Dr. Tourdjman commented. "And routine testing of asymptomatic children should not be recommended."

Public health officials agree that children with E. coli O157 (the most common serotype) should be excluded from child care until two consecutive negative stool samples are obtained, he noted by way of background. But because of a lack of data, there is no consensus when it comes to restrictions for children with E. coli O26, the second most common serotype.

The Oregon outbreak occurred in October 2010 at a child care center having 76 attendees aged 6 weeks to 12 years, Dr. Tourdjman reported at the conference, which was sponsored by the American Society for Microbiology.

Overall, 61 people – all 13 staff, all 41 attendees in four of five preschool classrooms, and all 7 school-aged siblings of those attendees – provided stool samples for testing.

Results showed that nine of the children and one of the staff were positive for Shiga toxin–producing E. coli O26, as determined by initial polymerase chain reaction for the toxin and confirmed by subsequent stool culture for typing.

Four of the 10 positive individuals, all children, had diarrhea, which was bloody in one case. But none experienced hemolytic uremic syndrome or other serious illness. Laboratory tests showed that all isolates matched and all produced only Shiga toxin type 1.

Of the nine infected children, two had consistently negative test results after their initial positive result. Among the other seven, the median duration of shedding in stool was 25 days, with a maximum of 46 days.

Half of the households of infected children agreed to testing to assess possible secondary transmission, and 14 of 17 household members provided stool samples. None were positive by polymerase chain reaction for Shiga toxin.

In the wake of the outbreak, the child care center was thoroughly cleaned and staff were trained in hygiene practices, according to Dr. Tourdjman. The children with diarrhea were excluded from the center, and the asymptomatic positive children were cohorted (separated from other children in a single classroom).

However, the cohorting was discontinued after 3 weeks given that all factors pointed to a low-virulence pathogen and there was strict compliance with the hygiene practices. "The decision to stop cohorting was not based on the results of the shedding study," he noted. "No symptoms were reported at the center after the discontinuation of cohorting."

Dr. Tourdjman did not report any relevant financial conflicts of interests.

CHICAGO – Escherichia coli O26 does not appear to cause severe disease in children, according to an epidemiologic study of a recent outbreak in an Oregon child care center.

In all, 60% of 10 infected children and staff were asymptomatic, and none developed illness more serious than diarrhea, investigators reported at the annual Interscience Conference on Antimicrobial Agents and Chemotherapy.

Shedding in the stool of infected children was prolonged, lasting up to 46 days, but there was no secondary transmission of the pathogen to household members.

Laboratory testing showed that the pathogen produced type 1 Shiga toxin but not type 2 Shiga toxin, which is seen in some other E. coli serotypes and carries a higher risk of hemolytic uremic syndrome.

In all, 60% of 10 infected children and staff were asymptomatic, and none developed illness more serious than diarrhea, investigators reported

"This study raised more questions than it answered," acknowledged lead investigator Dr. Mathieu Tourdjman, a Centers for Disease Control and Prevention Epidemic Intelligence Service officer with the Oregon Health Authority in Portland. But taken together, the findings generally point to a low-virulence pathogen.

This new information does not warrant any change to Oregon’s policy for child care settings when O26 is detected, according to Dr. Tourdjman. That policy requires that infected children be excluded until they have two consecutive negative stool samples, but allows the local health department to waive the exclusion at its discretion.

"In the context of an O26 Shiga toxin 1–only outbreak in a child care center, we continue to recommend that symptomatic children be excluded at least until symptoms resolve, and that the incidence of infection should be closely monitored," he said. "Routine hand washing before meals and before and after changing diapers and toileting should be emphasized."

And restriction criteria should remain flexible. "In the absence of severe disease, requiring two consecutive negative stool samples to lift the exclusion might not be justifiable," Dr. Tourdjman commented. "And routine testing of asymptomatic children should not be recommended."

Public health officials agree that children with E. coli O157 (the most common serotype) should be excluded from child care until two consecutive negative stool samples are obtained, he noted by way of background. But because of a lack of data, there is no consensus when it comes to restrictions for children with E. coli O26, the second most common serotype.

The Oregon outbreak occurred in October 2010 at a child care center having 76 attendees aged 6 weeks to 12 years, Dr. Tourdjman reported at the conference, which was sponsored by the American Society for Microbiology.

Overall, 61 people – all 13 staff, all 41 attendees in four of five preschool classrooms, and all 7 school-aged siblings of those attendees – provided stool samples for testing.

Results showed that nine of the children and one of the staff were positive for Shiga toxin–producing E. coli O26, as determined by initial polymerase chain reaction for the toxin and confirmed by subsequent stool culture for typing.

Four of the 10 positive individuals, all children, had diarrhea, which was bloody in one case. But none experienced hemolytic uremic syndrome or other serious illness. Laboratory tests showed that all isolates matched and all produced only Shiga toxin type 1.

Of the nine infected children, two had consistently negative test results after their initial positive result. Among the other seven, the median duration of shedding in stool was 25 days, with a maximum of 46 days.

Half of the households of infected children agreed to testing to assess possible secondary transmission, and 14 of 17 household members provided stool samples. None were positive by polymerase chain reaction for Shiga toxin.

In the wake of the outbreak, the child care center was thoroughly cleaned and staff were trained in hygiene practices, according to Dr. Tourdjman. The children with diarrhea were excluded from the center, and the asymptomatic positive children were cohorted (separated from other children in a single classroom).

However, the cohorting was discontinued after 3 weeks given that all factors pointed to a low-virulence pathogen and there was strict compliance with the hygiene practices. "The decision to stop cohorting was not based on the results of the shedding study," he noted. "No symptoms were reported at the center after the discontinuation of cohorting."

Dr. Tourdjman did not report any relevant financial conflicts of interests.