Characterization of Waterborne Outbreak–associated Campylobacter jejuni, Walkerton, Ontario

waterborne outbreak of 2000 resulted from entry of Escherichia coli O157:H7 and Campylobacter spp. from neighboring farms into the town water supply. Isolates of Campylobacter jejuni and Campylobacter coli obtained from outbreak investigations were characterized by phenotypic and genotypic methods, including heat-stable and heat-labile serotyping, phage typing , biotyping, fla–restriction fragment length polymorphism (RFLP) typing, and pulsed-field gel electrophoresis. Two main outbreak strains were identified on the basis of heat-stable serotyping and fla-RFLP typing. These strains produced a limited number of types when tested by other methods. Isolates with types indistinguishable from, or similar to, the outbreak types were found only on one farm near the town of Walkerton, whereas cattle from other farms carried a variety of Campylobacter strains with different type characteristics. Results of these analyses confirmed results from epidemiologic studies and the utility of using several different typing and subtyping methods for completely characterizing bacterial populations. A n outbreak of Campylobacter jejuni in a farming community in southern Ontario, Canada, in 1985 resulted from contamination of well water caused by spring runoff and heavy rains (1). In May 2000, a second waterborne outbreak of Escherichia coli O157:H7 and Campylobacter occurred in Bruce County, Ontario. Well water serving the town of Walkerton was contaminated by surface water carrying livestock waste immediately after heavy rains (2,3). A detailed microbiologic and epidemiologic analysis of the most recent outbreak may provide insights that could help make this type of outbreak less frequent. Most sporadic cases of campylobacteriosis are associated with preparation or consumption of poultry products (4). Outbreaks have been associated with consumption of unpasteurized milk or unchlorinated water (5). An estimated 20% of cases of illness caused by C. jejuni are due to vehicles of infection other than food, including water (6). Waterborne outbreaks of Campylobacter tend to occur in spring or early fall, an association attributed to seasonality of surface water contamination and infection in cattle herds (5). Contaminated water sources have been implicated in outbreaks involving E. coli O157:H7 and Campylobacter together in Scotland (7) and in New York State (8,9). The former outbreak resulted from sewage contamination of the water supply of a small village in Fife, Scotland. The latter outbreak was associated with contamination of wells at a state fair (10). Excrement from birds and animals, including cattle, has been shown to contaminate surface water supplies used by humans infected with Campylobacter (9). Campylobacter spp. have …