Campylobacter jejuni is the most common bacterial enteric pathogen in developed countries and is an important cause of traveler’s diarrhea. Most infections are associated with ingestion of improperly cooked chicken, but outbreaks also can be caused by unpasteurized milk or contaminated water.
The pathogenesis of Campylobacter infection remains poorly defined, but four major virulence properties contribute: motility, adherence, toxin production, and invasion. Flagella allow Campylobacter to be motile. This facilitates adherence and colonization, which are also necessary for mucosal invasion. Cytotoxins that cause epithelial damage and a cholera toxin–like enterotoxin are also released by some C. jejuni isolates. Dysentery or bloody diarrhea, is generally associated with invasion and only occurs with a small minority of Campylobacter strains. Enteric fever occurs when bacteria proliferate within the lamina propria and mesenteric lymph nodes.
Campylobacter infection can result in reactive arthritis, primarily in patients with HLA-B27. Other extraintestinal complications, including erythema nodosum and Guillain-Barré syndrome (Chapter 22), a flaccid paralysis caused by autoimmune-induced inflammation of peripheral nerves, are not HLA-linked. Fortunately, Guillain-Barré syndrome develops in 0.1% or less of individuals infected with
Campylobacter.
MORPHOLOGYCampylobacter, Shigella, Salmonella, andmanyotherbacterialinfections,includingYersinia andE. coli, allinduceasimilarmicroscopicpicture,termedacute self-limited colitis. Specificdiagnosisisprimarilybystoolculture.Thehistologyofacuteself-limitedcolitisincludesprominentlaminapropriaandintraepithelialneutrophilinfiltrates(
Fig.15.23A );cryptitis (neutrophilinfiltrationofthecrypts)andcrypt abscesses (cryptswithaccumulationsofluminalneutrophils)alsomaybepresent.Thepreservationofcryptarchitectureinmostcasesofacuteself-limitedcolitisishelpfulindistinguishingtheseinfectionsfromchronicinflammatoryillnessessuchasinflammatoryboweldisease(
Fig.15.23B
Ingestion of as few as 500 C. jejuni organisms can cause disease after an incubation period of up to 8 days. Watery diarrhea, either acute or with onset after an influenza like prodrome, is the primary manifestation, and dysentery develops in 15% to 50% of patients. Patients may shed bacteria for 1 month or more after clinical resolution. The disease is self-limited, and antibiotic therapy generally is not required.
Fig. 15.23 Bacterialenterocolitis.(A)Campylobacter jejuni infectionpro-ducesacute,self-limitedcolitis.Neutrophilscanbeseenwithinsurfaceandcryptepithelium,andacryptabscessispresent(lower right). (B)Enteroinva-siveEscherichia coli infectionissimilartootheracute,self-limitedcolitides.Notethemaintenanceofnormalcryptarchitectureandspacing,despiteabundantintraepithelialneutrophils.
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Shigella are gram-negative bacilli that are unencapsulated, nonmotile, facultative anaerobes responsible for one of the most common causes of bloody diarrhea. Shigellae are highly transmissible by the fecal-oral route or through ingestion of contaminated water and food; the infective dose is fewer than 100 organisms, and each gram of stool contains as many as 109 organisms during acute phases of the disease.