Content area
Full Text
Abstract
Escherichia coli O157:H7 has been associated with a number of waterborne outbreaks, but it has never been recovered
from an implicated environment. This paper reports on an August 1999 outbreak of E, coli O157:H7 associated with swimming in Battle Ground Lake in Clark County, Washington. E. coli O157:H7 was isolated from duck feces, as well as from two water samples. The authors used pulsed-field gel electrophoresis to compare these isolates with patent isolates for genetic homology. All the isolates yielded the same restriction fragment patterns. In addition, using polymerase chain reaction, the authors found patient isolates and environmental isolates to have the same virulence factors (Stx, eaeA, and hly).
Introduction
Escherichia coli O157:H7 has emerged as a significant foodborne and waterborne pathogen. Over the past two decades, reports of waterborne E. coli O157:H7 outbreaks attributed to drinking water or recreational contact have increased. The first reported isolation of E. coli O157:H7 from water came from a freshwater sample taken from a water reservoir (without any connection to human illness) in the countryside surrounding the city of Philadelphia (McGowan, Wickersham, & Strockbin, 1989).
The first reported outbreak of E. coli O157:H7 associated with recreational water occurred in the summer of 1991. The 1991 outbreak involved 21 cases of E. coli O157:H7 and 59 cases of Shigella sonnei infections, all associated with swimming in Blue Lake near Portland, Oregon (Keene et al., 1994). Four more outbreaks of E. coli O157:H7 have been epidemiologically linked to swimming in freshwater lakes (Ackman et al., 1997; Cransberg et al., 1996; Paunio et al., 1999; Waner et al., 1996). In several waterborne outbreaks of E. coli O157:H7, investigators were unable to isolate the pathogen from the suspected water (Ackman et al., 1997; Cransberg et al., 1996; Dev et al., 1984; Keene et al., 1994; Paunio et al., 1999; Swerdlow et al., 1992; Warner et al., 1996). In August 1999, 36 case patients developed E. coli O157:H7 infection. Most had a history of swimming in Battle Ground Lake (BGL) located in Battle Ground Lake State Park in Clark County, Washington (28 swimmers and 8 contacts of swimmers; 35 stool-culture confirmed, one serologically confirmed). The outbreak was detected through routine infectious-diseases surveillance by personnel of the Southwest Washington Health...