Abstract: 9264 A. Introduction

Campylobacter jejuni is the leading cause of bacterial diarrheal disease, causing more cases than Salmonella and Shigella combined. Most Campylobacter infections are sporadic, with few outbreaks.¹ Campylobacter infections also have been associated with Guillain-Barré syndrome.² Campylobacter spp. are ubiquitous in the environment and throughout the food chain.¹ Poultry,³ sheep,⁴ cattle,⁴ and wild birds⁵ have all been implicated as reservoirs for Campylobacter. They have been recovered from water, wastewater, and soil.⁶ Peak infections of Campylobacter occur in May and September.¹ Outbreaks of Campylobacter disease also have been associated with drinking raw milk¹ and private drinking water.⁷ In a study of 21 outbreaks of Campylobacter infections in England, 6 were traced to water, 5 to milk, 5 to food, and in 5 the source could not be identified.⁸ One difficulty in linking exposure to disease and identifying outbreaks is the approximately 2-week incubation period between exposure and disease. In addition, it remains difficult to distinguish pathogenic from nonpathogenic Campylobacter.¹

Campylobacter physiology is an important determinant of its presence in water and other environments. These bacteria are microaerophiles and grow at 3% to 5% oxygen and 2% to 10% CO₂.⁹ In the laboratory, Campylobacter spp. require a low redox potential for growth and are relatively sensitive to ultraviolet light and desiccation.⁶ The presence of Campylobacter in streams and rivers is associated with passage through farmland or the introduction of wastewater.⁶ Campylobacter spp. have also been recovered from groundwater, an environment that supports their physiological requirements. In water, the highest numbers of these bacteria are found in the winter months⁶ and thus do not correlate with the seasonal appearance of disease. Because Campylobacter bacteria do not grow in surface waters and die off rapidly, their numbers fall rapidly as the distance from the source increases.⁶ This explains why there is no significant association between Campylobacter presence in farmland and water beyond 600 m of the source.¹⁰ Further confounding our understanding of the epidemiology of Campylobacter disease is the low infectious dose and the presence of viable but nonculturable Campylobacter spp.¹¹

Because of the relatively fastidious requirements for growth, isolation from samples that contain other microorganisms can be increased substantially (e.g., 4-fold) by enrichment.