Campylobacter fetus is a rod-shaped, gram-negative species of bacteria within the genus Campylobacter of phylum Pseudomonadota. Identification of C. fetus species in infected animals or people is routinely performed by culture on blood or cefoperazone deoxycholate agar. Subspecies of C. fetus commonly causes reproductive disease in ruminants and gastrointestinal disease in humans. Transmission of C. fetus subspecies venerealis occurs mainly through venereal contact while transmission of C. fetus subspecies fetus occurs mainly through ingestion of bacteria in a contaminated environment. Infertility in cattle and abortion in sheep are common outcomes of infection associated with C. fetus subspecies venerealis and C. fetus subspecies fetus, respectively. Disease in humans occurs through zoonotic transmission of C. fetus mainly via ingestion of contaminated food or water sources. C. fetus can be diagnosed with polymerase chain reaction assays, enzyme linked immunosorbent assays and vaginal mucus agglutination testing. As vaccines are typically not efficient in preventing future spread, infected bulls are often culled. Human infections may be treated with erythromycin as antimicrobial resistance has been emerging for the fluoroquinolones. Morphology and identification On cytology, C. fetus is a gram-negative rod, though may present coccoid under suboptimal conditions. A distinguishing feature of C. fetus is the "S-shape" of the rod, resembling thin, helical spirochaetes. C. fetus can be a highly motile organism by means of a single, unsheathed flagellum. Genus identification based on motility may be possible due to their characteristic corkscrew-like movement. C. fetus are non-spore forming and microaerophilic organisms that are both catalase and oxidase-positive, but non-fermentative. Identification of C. fetus requires aseptic sample collection, followed by culture and potentially further biochemical and molecular methods. To increase the likelihood of successful growth, cultures on blood agar should be performed as soon as possible following collection. If samples are likely to be contaminated or faster growth is required, selective media or the use of antibiotics can be employed to inhibit growth of contaminants. Modified charcoal cefoperazone deoxycholate (CCD) agar is a growth medium designed to isolate Campylobacters from feces. On CCD agar, C. fetus will grow as grey colonies that may appear moist. Growth of C. fetus can be seen within 40–48 hours of incubation between 25-37 °C under microaerophilic conditions. Some, but not all species of C. fetus will grow at 42 °C. Because C. fetus is a fastidious organism to grow, positive cultures can be considered diagnostic, however negative cultures cannot rule out the