7.6.1 Isolation of Campylobacter species
All Campylobacter species are fastidious and relatively slow growers, and small colonies are evident on enriched media after 48–72h of incubation. There are many established protocols for the isolation and identification of C. jejuni and C. coli from animal faeces for surveillance and research purposes.
Diagnosis of C. fetus subspecies fetus relies on the isolation of the bacterium from fetal stomach, liver, lungs, or placental cotyledons. Sterile site lung and stomach specimens from aborted fetuses can be plated directly on blood agar plates and incubated in 3–5% CO2 for up to five days. Contaminated specimens will require inoculation onto selective media containing antibiotics, but such media may also inhibit the growth of many C. fetus strains.
C. fetus subspecies venerealis is more fastidious, with low recovery rates of culture reported worldwide. Hence, diagnosis of bovine genital campylobacteriosis is often done using PCR or other culture-free methods (see Section 5.4.4).
Genus identification is done phenotypically by assessing colony morphology, and the presence of typical gull-shaped, oxidase-positive, Gram-negative bacteria (Figure 20). Biochemical reactions allow a presumptive species identification. If needed, species-specific PCR or 16S rRNA gene sequencing can be done for species confirmation.
Campylobacter can be stored frozen or freeze dried, but viability drops significantly when stored at room temperature or refrigerated.
7.6 Campylobacter species
