GeneticAnalysis of the Capsule Locus of
            <i>Haemophilus influenzae</i>
            Serotypef

Satola, Sarah W.; Schirmer, Patricia; Farley, Monica M.

doi:10.1128/iai.71.12.7202-7207.2003

Cited by 35 publications

(30 citation statements)

References 46 publications

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“…The resulting PCR products were sequenced and analyzed. All 11 Hie strains were found to have the cap locus in the identical chromosomal location as that of H. influenzae serotype f (Hif), associated with the same flanking genes (sodC at the 5Ј end and HI1637 at the 3Ј end), confirming previous investigations (19). Sequence analysis of the two end junctions also revealed that they contained no sequences reminiscent of the insertion element IS1016.…”

supporting

confidence: 67%

“…Overall, region I exhibited 90% and 96% sequence identity to the previously described region I from Hib and Hif, respectively (18,19). Region I included four ORFs, which were named bexA, bexB, bexC, and bexD.…”

mentioning

confidence: 98%

“…In encapsulated H. influenzae strains, the genes for the production of the polysaccharide capsules are organized in a capsulation (cap) locus, which consists of three different functional regions (11,13). Regions I and III are common to all capsular types and contain genes necessary for transport and process of the capsular material, while region II contains serotype-specific biosynthesis genes (7,10,18,19,25).…”

mentioning

confidence: 99%

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Genetic Characterization of the Capsulation Locus of Haemophilus influenzae Serotype e

et al. 2010

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confidence: 67%

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confidence: 98%

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confidence: 99%

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Genetic Characterization of the Capsulation Locus of Haemophilus influenzae Serotype e

et al. 2010

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“…We detected sodC in 31 of 31 variant strains and in 1 (HK 2067 of serotype f) of 11 H. influenzae strains. sodC is located adjacent to bexA in encapsulated strains of phylogenetic group II (42,47) and has hitherto not been described in nonencapsulated strains.…”

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confidence: 99%

Delineation of the Species Haemophilus influenzae by Phenotype, Multilocus Sequence Phylogeny, and Detection of Marker Genes

2009

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To obtain more information on the much-debated definition of prokaryotic species, we investigated the borders of Haemophilus influenzae by comparative analysis of H. influenzae reference strains with closely related bacteria including strains assigned to Haemophilus haemolyticus, cryptic genospecies biotype IV, and the never formally validated species "Haemophilus intermedius". Multilocus sequence phylogeny based on six housekeeping genes separated a cluster encompassing the type and the reference strains of H. influenzae from 31 more distantly related strains. Comparison of 16S rRNA gene sequences supported this delineation but was obscured by a conspicuously high number of polymorphic sites in many of the strains that did not belong to the core group of H. influenzae strains. The division was corroborated by the differential presence of genes encoding H. influenzae adhesion and penetration protein, fuculokinase, and Cu,Zn-superoxide dismutase, whereas immunoglobulin A1 protease activity or the presence of the iga gene was of limited discriminatory value. The existence of porphyrin-synthesizing strains ("H. intermedius") closely related to H. influenzae was confirmed. Several chromosomally encoded hemin biosynthesis genes were identified, and sequence analysis showed these genes to represent an ancestral genotype rather than recent transfers from, e.g., Haemophilus parainfluenzae. Strains previously assigned to H. haemolyticus formed several separate lineages within a distinct but deeply branching cluster, intermingled with strains of "H. intermedius" and cryptic genospecies biotype IV. Although H. influenzae is phenotypically more homogenous than some other Haemophilus species, the genetic diversity and multicluster structure of strains traditionally associated with H. influenzae make it difficult to define the natural borders of that species.Bacterial diversity is usually expected to be organized into phenotypic and genetic clusters recognized as species. The diversity within species is thought to be confined by natural forces, although uncertainty exists as to the nature of the cohesion that constrains this diversity. There is increasing evidence that recombination occurs between distantly related bacteria and that barriers to this process, which could be used to define species naturally, are not always apparent (7, 11). As the bacterial species concept is central to taxonomy and evolutionary biology and has consequences for other disciplines such as the discrimination of pathogens from related bacteria with no pathogenic potential, there is a need to reevaluate to what extent accepted species are indeed coherent units.The gram-negative, nonmotile, facultatively anaerobic bacterium Haemophilus influenzae is a commensal organism of the pharynx frequently involved in localized infections of the respiratory tract, middle ear, and conjunctiva and sometimes in invasive infections such as meningitis or bacteremia. Presumptive identification is based on inability to synthesize NAD (V factor dependence) and porphyri...

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“…Primers and probes designed for the detection of H. influenzae capsular types a to f (Hia to Hif) were targeted within variable region II of the encapsulation cap locus (21). For the bexA gene, several sequence variations have been reported (10,12,18,19). We used the MegAlign program of DNASTAR, version 5.07 (Madison, WI), to compare 18 published bexA sequences (National Center for Biotechnology Information [NCBI] GenBank sequence database), and we chose a primerprobe combination situated in the most conserved regions.…”

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confidence: 99%

Real-Time PCR for Determining Capsular Serotypes of Haemophilus influenzae

et al. 2007

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A two-step real-time PCR assay targeting all six capsulation loci of Haemophilus influenzae (i.e., serotypes a to f) was developed and compared with a previously published qualitative PCR assay by using 131 H. influenzae clinical isolates. There was a 98.5% concordance between the two tests. The sensitivity of detection of capsular type-specific reference strains of H. influenzae a to c (10 1 CFU/PCR) was higher than that for type e (10 3 CFU/PCR) and types d and f (10 4 CFU/PCR), and a broader dynamic range was obtained (5 to 8 log 10 units). No cross-reaction was observed with bacteria commonly isolated from the respiratory tract. We showed that both PCR assays are more reliable than slide agglutination serotyping. The real-time PCR-based assay seems to be an alternative of choice for the epidemiological follow-up of H. influenzae invasive infections.

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GeneticAnalysis of the Capsule Locus of Haemophilus influenzae Serotypef

Cited by 35 publications

References 46 publications

Genetic Characterization of the Capsulation Locus of Haemophilus influenzae Serotype e

Genetic Characterization of the Capsulation Locus of Haemophilus influenzae Serotype e

Delineation of the Species Haemophilus influenzae by Phenotype, Multilocus Sequence Phylogeny, and Detection of Marker Genes

Real-Time PCR for Determining Capsular Serotypes of Haemophilus influenzae

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