Campylobacter, Arcobacter, and Helicobacter

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Campylobacter, Arcobacter, and Helicobacter

Because of morphologic similarities and an inability to recover these organisms using routine laboratory media for primary isolation, the genera Campylobacter, Arcobacter, and Helicobacter are considered in this chapter (Figure 34-1). All organisms belonging to these genera are small, curved, motile, gram-negative bacilli. With few exceptions, most of these bacteria also have a requirement for a microaerobic (5% to 10% O2) atmosphere.

Campylobacter and Arcobacter

General Characteristics

Campylobacter and Arcobacter spp. are relatively slow growing, fastidious, and, in general, asaccharolytic; organisms known to cause disease in humans are listed in Table 34-1.

TABLE 34-1

Campylobacter and Arcobacter spp., Their Source, and Spectrum of Disease in Humans

Organism Source Spectrum of Disease in Humans
C. concisus, C. curvus, C. rectus, C. showae Humans Periodontal disease; gastroenteritis (?)
C. gracilis Humans Deep-tissue infections: head, neck, and viscera; gingival crevices
C. coli Pigs, poultry, sheep, bulls, birds
C. jejuni subsp. jejuni Poultry, pigs, bulls, dogs, cats, birds, and other animals
C. jejuni subsp. doylei Humans
C. lari Birds, poultry, other animals; river and seawater
C. hyointestinalis subsp. hyointestinalis Pigs, cattle, hamsters, deer Gastroenteritis
C. upsaliensis Dogs, cats
C. fetus subsp. fetus Cattle, sheep
C. fetus subsp. venerealis Cattle Septicemia
C. sputorum biovar sputorum Humans, cattle, pigs
Arcobacter cryaerophilus Pigs, bulls, and other animals
A. butzleri Pigs, bulls, humans, other animals; water

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*Most common clinical presentation.

Epidemiology and Pathogenesis

The majority of Campylobacter species are pathogenic and associated with a wide variety of diseases in humans and other animals. These organisms demonstrate considerable ecologic diversity. Campylobacter spp. are microaerophilic (5% to 10% O2) inhabitants of the gastrointestinal tracts of various animals, including poultry, dogs, cats, sheep, and cattle, as well as the reproductive organs of several species. When random fecal samples from chicken carcasses from butcher shops in the New York City area were tested for Campylobacter, 83% of the samples yielded more than 10 colony-forming units per gram of feces. In general, Campylobacter spp. produce three syndromes in humans: febrile systemic disease, periodontal disease, and, most commonly, gastroenteritis. Arcobacter species appear to be associated with gastroenteritis. Studies have indicated that A. butzleri was the fourth most common Campylobacter-like organism isolated from stool and was associated with a persistent, watery diarrhea. In addition, more recent data indicate that Arcobacter is underreported in gastrointestinal infections and diarrhea throughout many European countries. The organism is found in the environment and in untreated water. It is also prevalent in commercially prepared meats including chicken, beef, pork, lamb, and poultry.

Within the genus Campylobacter, C. jejuni and C. coli are commonly associated with infections in humans and are transmitted via contaminated food, milk, or water. Outbreaks have been associated with contaminated drinking water and improperly pasteurized milk, among other sources. In contrast to other agents of foodborne gastroenteritis, including Salmonella and staphylococci, Campylobacter spp. does not multiply in food. Other campylobacters have been isolated from patients as a result of consumption of untreated water, immunocompromised patients, or patients recently returned from international travel. C. jejuni subsp. doylei has been isolated from children with diarrhea and from gastric biopsies in adults. In developed countries, the majority of C. jejuni infections are transmitted by direct contact during the preparation and eating of chicken. Person-to-person transmission of Campylobacter infections plays only a minor role in the transmission of disease. There is a marked seasonality with the rates of C. jejuni infection in the United States; the highest rates of infection occur in late summer and early fall. Campylobacter spp. has been recognized as the most common etiologic agent of gastroenteritis in the United States.

Although infections with C. jejuni are evident as a result of acute inflammatory enteritis of the small intestine and colon, the pathogenesis remains unclear. However, multiplication of organisms in the intestine leads to cell damage and an inflammatory response. Blood and polymorphonuclear neutrophils are often observed in patient stool specimens. Most strains of C. jejuni are susceptible to the nonspecific bactericidal activity of normal human serum; this susceptibility probably explains why C. jejuni bacteremia is uncommon.

Spectrum of Disease

As previously mentioned, Campylobacter species are the causative agent of gastrointestinal or extraintestinal infections. An increase in extraintestinal disease, including meningitis, endocarditis, and septic arthritis has been reported in patients with acquired immunodeficiency syndrome (AIDS) and other immunocompromised individuals. The different campylobacters and the associated diseases are summarized in Table 34-1. Gastroenteritis associated with Campylobacter spp. is usually a self-limiting illness and does not require antibiotic therapy. Most recently, postinfectious complications with C. jejuni have been recognized and include reactive arthritis and Guillain-Barré syndrome, an acute demyelination (removal of the myelin sheath from a nerve) of the peripheral nerves. Studies indicate that 20% to 40% of patients with this syndrome are infected with C. jejuni 1 to 3 weeks prior to the onset of neurologic symptoms.

Laboratory Diagnosis

Specimen Collection, Transport, and Processing

There are no special requirements for the collection, transport, and processing of clinical specimens for the detection of campylobacters; the two most common clinical specimens submitted to the laboratory are feces (rectal swabs are also acceptable for culture) and blood. Specimens should be processed as soon as possible. Delays of more than 2 hours require the stool specimen to be placed either in Cary-Blair transport medium or in campy thio, a thioglycollate broth base with 0.16% agar and vancomycin (10 mg/L), trimethoprim (5 mg/L), cephalothin (15 mg/L), polymyxin B (2500 U/L), and amphotericin B (2 mg/L). Cary-Blair transport medium is suitable for other enteric pathogens; specimens received in transport medium should be processed immediately or stored at 4° C until processed.

Direct Detection

Upon gram staining, Campylobacter spp. display a characteristic microscopic morphology as small, curved or seagull-winged, faintly staining, gram-negative rods (Figure 34-2). Polymerase chain reaction (PCR) amplification may provide an alternative to culture methods for the detection of Campylobacter spp. from clinical specimens. The detection of Campylobacter DNA in stools from a large number of patients with diarrhea suggests that Campylobacter spp. other than C. jejuni and C. coli may account for a proportion of cases of acute gastroenteritis in which no etiologic agent is identified.

Cultivation

Stool.

Successful isolation of Campylobacter spp. from stool requires selective media and optimum incubation conditions. Recommended inoculation of two selective agars is associated with increased recovery of the organisms. Because Campylobacter and Arcobacter spp. have different optimum temperatures, two sets of selective plates should be incubated, one at 42° C and one at 37° C. Extended incubation may be required, 48 to 72 hours, before there is evidence of visible growth. Table 34-2 describes the selective plating media and incubation conditions required for the recovery of Campylobacter spp. from stool specimens.

42° C microaerobic conditions* for 72 hours 37° C under microaerobic conditions for at least 72 hours up to 7 days A. cryaerophilus, A. butzleri Campy-CVA 37° C under microaerobic conditions§ for 72 hours

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*Atmosphere can be generated in several ways, including commercially produced, gas-generating envelopes to be used with plastic bags or jars. Evacuation and replacement in plastic bags or anaerobic jars with an atmosphere of 10% CO2

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