Complications are rare although reactive arthritis can develop and
Campylobacterhas been shown to cause the serious neurological disease,
Guillain–Barre syndrome.
As with other pathogens the infective dose will depend upon a number
of factors including the virulence of the strain, the vehicle with which it is
ingested and the susceptibility of the individual. Young adults (15–24
years old) and young children (1–4 years) appear particularly susceptible.
In an outbreak at a boys’ school in England caused by contamination of
a water-holding tank with bird droppings, the infective dose was esti-
mated as 500 organisms and in a separate study, a similar dose in milk
caused illness in a volunteer. Motility, chemotaxis and the corkscrew
morphology of the cells are all important factors in the virulence of
Campylobacter, enabling it to penetrate the viscous mucus which covers
the epithelial surface of the gut. Studies withC. jejunihave demonstrated
a chemotactic response toward the sugarL-fucose, a number of amino
acids, and intestinal mucus from mice and pigs. AlthoughCampylobacter
does not normally possess fimbriae it probably possesses other adhesins
that enable it to adhere to epithelial cells once the mucosal barrier has
been penetrated. The production of peritrichous ‘pili-like’ appendages
when cells are grown in the presence of bile has been observed. A
nonpiliated mutant did not show any reduced adherence or invasion in
a cell line although it did produce significantly reduced disease symptoms
in an animal model.
There is considerable uncertainty as to the precise mechanisms by
whichCampylobactercauses illness. It has been shown to be invasive in
cell cultures and a number of toxins with cholera-like or cytotoxic
activity have been described. Their role in pathogenesis however has
been brought into question following the complete sequencing of the
Campylobactergenome which has failed to identify sequences associated
with known toxins. One exception is the so-called cytolethal distending
toxin which has also been reported in a small number ofE. coliand
Shigellastrains. There is evidence that some of the pathogenic features of
the illness are the result of the body’s inflammatory response to invasion
by the organism, a factor also implicated in illness caused bySalmonella.
7.4.4 Isolation and Identification
Although most of the isolation procedures and media used were designed
forC. jejuni, they are also suitable forC. coliandC. laridis.
Pathogenic campylobacters have a reputation for being difficult to
grow but in fact their nutritional requirements are not particularly
complex and they can be grown on a number of peptone-based media
including nutrient broth. Where problems can sometimes arise is in their
sensitivitiy to oxygen and its reactive derivatives. Although pathogenic
Chapter 7 195