INTRODUCTION

Campylobacters are small gram-negative bacteria first recognized as causes of abortion in cattle and sheep in the early twentieth century [1]. A few decades later, the organism (originally called Vibrio) was reported as an occasional cause of illness in humans [2]. In 1973, a new genus, Campylobacter, was designated [3]. It was not until the 1980s that the full impact of Campylobacter infections on human health began to be appreciated; they are now known to be a leading cause of acute diarrhea worldwide. (See "Epidemiology and causes of acute diarrhea in developed countries".)

Campylobacter spp are common commensals in the gastrointestinal tract of animals, especially poultry; thus, animal-to-human transmission of infections occurs frequently. The microbiology, pathogenesis, and epidemiology of Campylobacter infection will be reviewed here. The clinical features and treatment of Campylobacter infection are discussed separately. (See "Clinical manifestations, diagnosis, and treatment of Campylobacter infection".)

MICROBIOLOGY

Campylobacters belong to a distinct group of specialized gram-negative bacteria designated rRNA superfamily VI [4]. Apart from the genus Campylobacter, the group also contains Arcobacter and Helicobacter. Arcobacters are closely related to campylobacters, and some cause intestinal infection in humans. Helicobacter pylori is well known as a cause of gastritis and peptic ulcer disease, but there are other Helicobacter species that cause infection of the human gut. (See "Infection with less common Campylobacter species and related bacteria" and "Pathophysiology of and immune response to Helicobacter pylori infection".)

A feature common to all these bacteria is that they are adapted to colonize the surface of the mucous membranes of the alimentary and reproductive tracts. This adaptation is reflected in their morphology. The combination of spiral shape and long polar flagella leads to rapid motility that enables the organisms to "corkscrew" their way through mucus with a facility denied to conventional bacteria (picture 1).

Most members of this group are microaerophilic, or partially anaerobic, and most undergo transformation into coccoid forms when exposed to adverse conditions, especially oxidation [5]. These appear to be degenerative forms, but some believe they are potentially dormant forms capable of long survival [6]. Although some campylobacters can survive in cold water for several weeks, even months, they are not necessarily in coccal form. In general, these bacteria are fragile and easily destroyed by heat, desiccation, acidity, irradiation, and disinfectants.