Human Infections with New Subspecies of Campylobacter fetus

Mary E. Patrick

, Maarten J. Gilbert, Martin J. Blaser, Robert V. Tauxe, Jaap A. Wagenaar, and Collette Fitzgerald

Author affiliations: Centers for Disease Control and Prevention, Atlanta, Georgia, USA (M.E. Patrick, R.V. Tauxe, C. Fitzgerald); Utrecht University, Utrecht, the Netherlands (M.J. Gilbert, J.A. Wagenaar); New York University School of Medicine, New York, New York, USA (M.J. Blaser); Central Veterinary Institute, Lelystad, the Netherlands (J. Wagenaar); World Health Organization Collaborating Center for Campylobacter/World Organisation for Animal Health Reference Laboratory for Campylobacteriosis, Utrecht (J.A. Wagenaar, M.J. Gilbert)

Abstract

Campylobacter fetus subsp. testudinum subsp. nov. is a newly proposed subspecies of C. fetus with markers of reptile origin. We summarize epidemiologic information for 9 humans infected with this bacterium. All cases were in men, most of whom were of Asian origin. Infection might have been related to exposure to Asian foods or reptiles.

Campylobacter spp. are the most common cause of bacterial gastrointestinal illness in humans. C. jejuni is the most common species and accounts for > 88% of reported cases in the United States (1). C. fetus is an uncommonly reported species that typically affects `immunocompromised, pregnant, or elderly persons and causes severe infections, including bacteremia and meningitis (2).
Two subspecies of C. fetus have been described: C. fetus subsp. fetus and C. fetus subsp. venerealis (3). C. fetus subsp. fetus has been isolated from intestinal tracts of sheep and cattle and from tissues from sporadic abortions in these species. C. fetus subsp. venerealis is restricted to cattle and causes bovine genital campylobacteriosis (4). Although C. fetus subsp. venerealis has been isolated from humans (5), its role in human disease is uncertain; most cases of C. fetus infection are caused by C. fetus subsp. fetus.
In 1984, C. fetus was isolated from feces of a reptile, a Florida box turtle (Terrapene carolina bauri) that was kept as a pet (6). C. fetus has also been isolated from feces of a healthy western hognose snake (Heterodon nasicus) and a blotched blue-tongue lizard (Tiliqua nigrolutea) that had unformed feces and was losing weight (7). Substantial genetic divergence between C. fetus strains of reptile and mammal origin has been demonstrated (8).
A human isolate of C. fetus with markers of reptile origin was reported in 2004 (9). A subsequent study involving phenotypic and molecular characterization of the 2004 human case, 4 additional human cases, and 3 reptiles definitively identified this collection of strains as a newly proposed subspecies named C. fetus subsp. testudinum subsp. nov. (7,10). The Centers for Disease Control and Prevention recently screened Campylobacter strains from its historical culture collection and identified 4 additional human cases of infection with this subspecies.