An uncommon Helicobacter isolate from blood: evidence of a group of Helicobacter spp. pathogenic in AIDS patients

Abstract

An unusual Helicobacter sp. was isolated from the blood of a human immunodeficiency virus (HIV)-infected patient. This organism had spiral morphology, with single amphitrichous flagella, and was negative for hippurate hydrolysis, production of urease, and reduction of nitrate. 16S rRNA gene sequence analysis verified that the isolate was a species of Helicobacter, most closely related to an undescribed Helicobacter-like isolate from Vancouver, British Columbia, Canada, and to Helicobacter westmeadii, a recently described species from Australia. Both organisms had also been isolated from the blood of HIV-infected patients. These blood isolates, along with Helicobacter cinaedi, form a cluster of closely related Helicobacter spp. that may represent an emerging group of pathogens in immunocompromised patients.

FIG. 1

Negatively stained transmission electron micrograph of VA isolate. Spiral form and single bipolar flagella are evident. Bar = 0.90 mm.

FIG. 2

Phylogenetic tree delineating the relationship between the 16S rRNA gene sequence for the VA isolate and sequences available in GenBank. Scale represents percent homology. Asterisks indicate species isolated from human blood.