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Category: Clinical Microbiology
Helicobacter * , Page 1 of 2
< Previous page | Next page > /docserver/preview/fulltext/10.1128/9781555816728/9781555814632_Chap54-1.gif /docserver/preview/fulltext/10.1128/9781555816728/9781555814632_Chap54-2.gifAbstract:
The genus Helicobacter is classified in the family "Helicobacteraceae" of the class Epsilonproteobacteria, formerly known as the epsilon subclass of the Proteobacteria, with Helicobacter pylori as the type species. Phylogenetic analyses reliant on 16S rRNA gene sequences alone have sensitivity limitations in investigations of closely related helicobacters, which have a high degree of natural transformation and genetic plasticity. Further insights into the taxonomy of the genus are now possible with the availability of complete genome sequences for five strains of H. pylori, and for strains of H. acinonychis, H. canadensis, and H. hepaticus. Enterohepatic helicobacters inhabit the intestinal and hepatobiliary tracts of various mammal and bird hosts, and several species, such as H. bilis, H. canadensis, H. canis, H. cinaedi, H. fennelliae, H. pullorum, and “H. winghamensis,” infect humans with clinical symptoms. From the microbiology laboratory perspective, microscopic examinations of a smear prepared directly from a biopsy specimen or from imprint cytology provide rapid bacteriological test results for observation of cells of H. pylori. There is currently no ”gold standard” method for use in the clinical laboratory setting for PCR of gastric biopsy specimens, and so it is advised that PCR based assays should not be the sole basis of determining the H. pylori status of a patient. To perform antimicrobial susceptibility testing, bacteriological culture of H. pylori from gastric biopsy specimens is recommended, especially in cases of repeated treatment failure.
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Phylogenetic tree of the genus Helicobacter based on 16S rRNA gene sequence similarity constructed using the neighbor-joining method. The bar represents percentage sequence divergence. Species marked in boldface type are urease positive; those in lightface are urease negative. * indicates species for which a genome sequence either is available or currently is being determined. Strain collection catalogue and 16S rRNA gene sequence reference numbers (in parentheses) are given where available.
Phylogenetic tree of the genus Helicobacter based on 16S rRNA gene sequence similarity constructed using the neighbor-joining method. The bar represents percentage sequence divergence. Species marked in boldface type are urease positive; those in lightface are urease negative. * indicates species for which a genome sequence either is available or currently is being determined. Strain collection catalogue and 16S rRNA gene sequence reference numbers (in parentheses) are given where available.
Helicobacter species, hosts, and disease spectrum
Helicobacter species, hosts, and disease spectrum
Key characteristics for identification of Helicobacter species a
a Test results from Baele et al. ( 5 ) and Fox and Megraud ( 39 ) and formal species descriptions. +, positive; –, negative; W, weakly positive; ND, not determined; Nal, nalidixic acid; Ceph, cephalexin; R, resistant; S, susceptible.
b B, bipolar; M, monopolar; P, peritrichous.
Key characteristics for identification of Helicobacter species a
a Test results from Baele et al. ( 5 ) and Fox and Megraud ( 39 ) and formal species descriptions. +, positive; –, negative; W, weakly positive; ND, not determined; Nal, nalidixic acid; Ceph, cephalexin; R, resistant; S, susceptible.
b B, bipolar; M, monopolar; P, peritrichous.