Campylobacter

ORGANISM:

GENERAL CONCEPTS:

The genus Campylobacter is a relatively recently discovered important human pathogen. The reason for this is that the organisms are microaerophilic, requiring low concentrations of oxygen only. Indeed, Campylobacter infections occur more often than Salmonella and Shigella diarrheas combined. In the United States, there are about 2 million cases annually, most among college students.

DISTINCTIVE PROPERTIES:

Campylobacter jejuni
Agricultural Research Service.
Photo by De Wood; digital colorization by Chris Pooley.

Campylobacters are Gram-negative, curved rods (the name derives from the Greek "campylo", meaning curved). These organisms are microaerophilic and motile.
Campylobacters possess a typical Gram-negative cell wall containing LPS endotoxin.
There are approximately 50 heat-labile "K" (capsular) and "H" (flagellar) antigens and 60 different heat-stable "O" (somatic) antigens associated with different species of Campylobacter.
These organisms are able to use amino acids and citric acid cycle intermediates for growth. C. jejuni grows best at 42°.

PATHOGENESIS:

A relatively small inoculum is required to cause illness; as few as 800 bacteria can produce disease in healthy persons.
Illness generally occurs following a 2-4 day incubation period when the bacteria multiply in the intestine, reaching numbers similar to Salmonella and Shigella infections (10⁶-10⁹ per gram of feces). Symptoms resemble an acute enteritis with fever, diarrhea, nausea and abdominal pain. The illness is generally self-limiting but may last a week.
C. jejuni appears to produce an enterotoxin similar to both the cholera and Escherichia coli toxins.

HOST DEFENSES:

Host defense mechanisms that help to combat Campylobacter infections are not well characterized but gastric acidity and secretory IgA may be important.

EPIDEMIOLOGY:

The genus Campylobacter is widely distributed among cattle, sheep, dogs, cats and other animals, existing as normal flora commensals.
Human infection results from the ingestion of contaminated water, milk or undercooked foods. Outbreaks resulting from ingestion of raw clams have been reported.

DIAGNOSIS:

Clinical: Clinical diagnosis is difficult since the symptomology is non-specific.
Laboratory: Special methods are required for isolation. Growth occurs in 5% O₂, 10% CO₂, 85% N₂ at 42°. A Gram stain of fecal material may reveal curved ("seagull" or "comma") shaped organisms.

CONTROL:

Sanitary: As with other fecal-oral diseases, sanitary means of control are most important. Proper disposal of feces, cooking foods, etc. can prevent disease.
Immunological: None available.
Chemotherapeutic: Erythromycin or tetracycline can be used for severe or prolonged illness.