Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
Other Campylobacter Species
The genus Campylobacter includes approximately 26 species and 9 subspecies. Of the Campylobacter species that are associated with human disease, C. jejuni is the prototype for enteric infections, and C. fetus is the prototype for extraintestinal infections. Campylobacter species other than C. jejuni and C. coli are estimated to comprise 3% of Campylobacter isolates isolated from stool. Refinement of microbiologic techniques for isolation of Campylobacter species and use of molecular assays have expanded our knowledge about the diversity of Campylobacter species and the spectrum of human infections associated with these organisms. However, Campylobacter species other than C. jejuni and C. coli may be significantly underdiagnosed as causes of gastrointestinal tract disease because selective Campylobacter media and incubation conditions may inhibit their growth, and similarities between their biochemical characteristics may make species identification difficult.
Phylogenetic trees have been established for Campylobacter on the basis of 16S ribosomal DNA sequences. These trees contain three distinct clades (species groups) ( Table 164.1 ). The first clade includes C. fetus and C. hyointestinalis , which are generally associated with disease in farm animals. The second clade includes C. coli, C. jejuni, C. lari, and C. upsaliensis species, which are associated with gastroenteritis in humans. The third includes C. curvus, C. concisus, C. gracilis, C. rectus, C. showae, and C. sputorum , which are associated with the periodontal cavity of humans and animals. C. jejuni and C. coli are described in Chapter 163 .
TABLE 164.1
Location of and Disease Associated With Campylobacter Species
| Association or Disease | Campylobacter Species |
|---|---|
| Disease in farm animals | Campylobacter fetus a Campylobacter hyointestinalis a |
| Gastroenteritis and rarely bacteremia | Campylobacter coli a Campylobacter jejuni a Campylobacter helveticus Campylobacter lari a Campylobacter upsaliensis a |
| Periodontal cavities of humans and animals | Campylobacter curvus Campylobacter concisus Campylobacter gracilis Campylobacter rectus Campylobacter showae Campylobacter sputorum |
Campylobacter Fetus
In 1913 McFadyean and Stockman found a Vibrio -like organism in aborted ovine fetuses and proposed the name Vibrio fetus ovis . The same organism later was implicated as a cause of abortion and infertility in other domestic animals, and the name was shortened to V. fetus . A second type of infection in cattle and sheep, causing sporadic abortion, but not infertility, was recognized; the causal agent was named V. fetus subsp. venerealis . In 1947 Vincent and colleagues reported the first human infection by C. fetus in a pregnant woman with a bloodstream infection (BSI) who aborted at 6 months of gestation. Currently, three subspecies of C. fetus have been recognized: C. fetus subsp. fetus , venerealis , and testudinum . , C. fetus subsp. venerealis is rarely associated with human disease. C. fetus subsp. fetus is predominantly associated with gastrointestinal illness but can cause BSI in those with underlying risk factors given its predilection for vascular endothelium, as well as perinatal infections. C. fetus subsp. testudinum was recently recognized as an organism associated with bacteremia and diarrhea in adult men, most of whom had reptile exposure. It appears to be an opportunistic pathogen, affecting immunocompromised or elderly individuals.
Microbiology and Epidemiology
C. fetus subsp. fetus are curved, motile, gram-negative, microaerophilic bacteria that are oxidase, catalase, and nitrate-positive; they grow at 25°–37°C but not at 42°C. It is estimated that at least 20% of C. fetus infections are undetected since isolation is typically performed at 42°C. Classically, C fetus subsp. fetus has been distinguished from subsp. venerealis as it shows 1% glycine resistance and production of H2S in L-cysteine media, whereas venerealis fails to grow in glycine and does not produce H2S. Subspecies identification can be accurately determined by 16s ribosomal sequencing. Matrix-assisted laser desorption ionization−time of flight (MALDI-TOF) and polymerase chain reaction (PCR) have proven to be less reliable methods, particularly for differentiation of C. fetus subsp. fetus from venerealis .
A paracrystalline protein structure composed of S-layer proteins surrounding the bacterial outer membrane is a unique virulence factor of C. fetus and C. rectus . This structure is implicated in invasion, resistance to phagocytosis, complement-mediated killing, and immune evasion by antigenic variation. Multiple case reports of infective prosthetic endocarditis resulted in the discovery that C fetus subsp. fetus has biofilm forming capability, although the mechanism is poorly understood.
Compared with other Campylobacter -infected patients, C. fetus is associated with male sex, hospitalization, and BSI. Although C. fetus accounts for 0.3–3.9% of all Campylobacter isolates, it is identified in 19%–53% of Campylobacter bacteremia. A source of C. fetus infection seldom is identified, although cases have been reported with cattle or sheep exposure, after ingestion of raw milk or contaminated food or water, by sexual and transplacental transmission, and in neonates after vaginal delivery.
In adults, nearly 75% of reported C. fetus infections are in men, and an estimated 42%–74% of systemic cases occur in patients with underlying conditions such as liver disease, diabetes mellitus, medical devices, HIV infection, and malignancy. , , , , However, there is an increased risk for infection among healthy elderly individuals and pregnant women. , Although uncommon, C. fetus infection during pregnancy can result in birth complications and systemic infection of the neonate. , C. fetus infections in children are usually confined to the neonatal period in association with maternal infection, but case reports of infection in children with underlying disease describe C. fetus septicemia, hepatitis, and pericarditis. ,
You're Reading a Preview
Become a Clinical Tree membership for Full access and enjoy Unlimited articles
If you are a member. Log in here