Submitted to: BMC Microbiology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 2/28/2007
Publication Date: 2/28/2007
Citation: Miller, W.G., Parker, C., Heath, S., Lastovica, A. 2007. Identification of genomic differences between campylobacter jejuni subsp. jejuni and C. jejuni subsp. doylei at the nap locus leads to the development of a C. jejuni subspeciation multiplex pcr method. BioMed Central Microbiology. 7:11. Interpretive Summary: The human bacterial pathogen, Campylobacter jejuni, is the primary cause of human bacterial gastroenteritis in the world. C. jejuni is composed of two subspecies, C. jejuni subsp. jejuni and C. jejuni subsp. doylei. Infection with either of these two subspecies can lead to different clinical outcomes with C. jejuni subsp. doylei infection leading more often to blood-borne disease (bacteremia/septicemia). Because of this, we developed a simple, inexpensive assay that can be used to distinguish between the two subspecies in a matter of hours, decreasing the identification time by at least 90%. This assay can also be used simultaneously to identify other potentially important Campylobacter spp also implicated in human illness. Additionally, we compared the DNA sequence of the two subspecies and found that the C. jejuni subsp. doylei strains are missing an important cell-killing toxin. Finally, further analysis suggests strongly that C. jejuni subsp. doylei arose from a single evolutionary event, i.e. C. jejuni subsp. doylei strains all share a common ancestor and that C. jejuni subsp. doylei strains may be an offshoot of a small group of doylei-like C. jejuni subsp. jejuni strains.
Technical Abstract: The human bacterial pathogen Campylobacter jejuni contains two subspecies: C. jejuni subsp. jejuni (Cjj) and C. jejuni subsp. doylei (Cjd). Although Cjd strains are isolated infrequently in many parts of the world, they are obtained primarily from human clinical samples and result in an unusual clinical symptomatology in that, in addtion to gastroenteritis, they are associated often with bacteremia. In this study, we describe a novel multiplex PCR method that can be used to unambiguously subspeciate C. jejuni isolates. This method correctly subspeciated 188 Cjj and Cjd isolates. In addition, combination of this multiplex PCR with a recently described lpxA-based speciation PCR method permits speciation and subspeciation of thermophilic Campylobacter spp. in a single amplification. We also present, for the first time, a genomic comparison of the two C. jejuni subspecies, using DNA microarray-based comparative genomic hybridization and MALDI-TOF mass spectrometry. Multiple metabolic, transport and virulence functions (e.g. cytolethal distending toxin) are shown to be variable between the two subspecies. Comparison of the two subspecies yields not only intriguing insights into potential differences in virulence but also provides clues as to the potential evolutionary origin of Cjd.