A cluster of Escherichia coli O157: nonmotile infections associated with recreational exposure to lake water.
OBJECTIVE
To identify cases and determine risk factors for an outbreak of Escherichia coli (E. coli) O157: nonmotile (NM) infections in children attending a summer day care program in California.


METHODS
The authors conducted a retrospective cohort study; the cohort comprised first and second graders who attended the day care program during the last week in August 1999. Shiga toxin testing and molecular subtyping using pulsed-field gel electrophoresis were performed on isolates. Lake water, lake bottom sediment samples, and waterfowl feces from the lake environs were cultured for E. coli O157.


RESULTS
Three cases of Shiga toxin-producing E. coli O157: NM infections with matching pulsed-field gel electrophoresis patterns and four probable cases were found. Children who swallowed more than a mouthful of water had a higher attack rate than those who swallowed less than a mouthful or none at all (43% vs. 10%, relative risk = 4.43, 95% confidence interval 1.12, 17.50).


CONCLUSIONS
E. coli O157: NM infections were associated with swallowing water from a freshwater lake. Potential sources of contamination include feces from humans, cattle, or deer. This outbreak illustrates the value in screening patients with diarrhea for E. coli O157, submitting isolates to public health laboratories, and using molecular techniques to identify related cases. Outbreaks associated with contaminated freshwater could be averted by prevention and early detection of contamination.
Feldman
Katherine A
KA
California Epidemiologic Investigation Service, California Department of Health Services, Sacramento, CA, USA. kfeldman@dhs.ca.gov
Mohle-Boetani
Janet C
JC
Ward
Judy
J
Furst
Karen
K
Abbott
Sharon L
SL
Ferrero
Dennis V
DV
Olsen
Alfred
A
Werner
S Benson
SB
D002140:California / Q000453:epidemiology; D002648:Child; D002656:Child Day Care Centers; D016000:Cluster Analysis; D015331:Cohort Studies; D003092:Colitis / Q000175:diagnosis / Q000453:epidemiology / Q000382:microbiology; D003967:Diarrhea / Q000453:epidemiology / Q000382:microbiology; D004196:Disease Outbreaks; D016521:Electrophoresis, Gel, Pulsed-Field; D004927:Escherichia coli Infections / Q000175:diagnosis / Q000453:epidemiology* / Q000635:transmission; D019453:Escherichia coli O157; D006801:Humans; D011998:Recreation; D012189:Retrospective Studies; D012307:Risk Factors; D022603:Shiga Toxins / Q000302:isolation & purification; D014871:Water Microbiology; D014873:Water Pollutants / Q000032:analysis
D022603:Shiga Toxins; D014873:Water Pollutants