Testing and Clearance Issues Faced in a Daycare
Outbreak of Non-O157 Enterhemorrhagic E. coli
Edwards L1, Black M2,
Glenn A1, Young S1, Parajon D3,
Oussova T1, Blythe D1
1Maryland Department of Health and Mental Hygiene, Baltimore,
Maryland, 2Howard County Department
of Health, Columbia, Maryland, 3Johns Hopkins School
of Hygiene and Public Health, Baltimore, Maryland.
Background: Important to controlling daycare outbreaks
of enterohemorrhagic E. coli (EHEC) is identifying and excluding
persons capable of infecting others. For some non-O157 EHEC outbreaks
only EHEC toxin assays, and not cultures, can be used to identify
EHEC in stool. We describe aspects of one such daycare outbreak,
including duration of positive toxin assays among children and adults
and exclusion from daycare.
Methods: After receiving a report of a case of
EHEC in a child attending daycare, a questionnaire was administered
to parents of daycare children, the daycare operator, and their
close contacts. All daycare attendees and symptomatic contacts were
evaluated. Stools were tested using a commercially-available EIA
test for the detection of Shiga-like Toxins I and II, and were examined
for presence of E. coli O157:H7. Persons were excluded from attending
or working at the daycare until they submitted two stool specimens
that were consecutively negative for EHEC toxin.
Results: Of the 30 persons interviewed, 19 (63%)
reported recent gastroenteritis. Only one had bloody stools. Seventeen
people were tested for EHEC. Toxin was detected in stools from five,
including four of 13 symptomatic and one of four asymptomatic people.
The five included three daycare children, one parent, and the daycare
operator. No sorbitol non-fermenter was isolated and O157 antigen
was not detected. The toxin-producing E. coli could not be identified.
For daycare children, the median time from symptom onset to the
collection of the second EHEC-toxin negative stool was 39 days (range:
36 – 40 days). During the clearance process, four of the five
(80%) cases submitted at least one negative stool for EHEC that
was subsequently followed by a positive stool.
Conclusions: This outbreak of non-O157 EHEC in
a daycare illustrates the need for individuals to submit two consecutively
negative stools for EHEC prior to readmission to daycare. Even though
the process is inconvenient and costly for parents and daycare operators,
provisions must be taken to assure that the EHEC toxin has been
cleared in order to prevent further transmission at the daycare.
Maryland Department of
Health & Mental Hygiene — Epidemiology & Disease Control
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