Induction of competence in nonencapsulated and encapsulated strains ofHaemophilus influenzae

Gromkova, Rosa; Rowji, Pradeep; Koornhof, H. J.

doi:10.1007/bf01570169

Cited by 15 publications

(12 citation statements)

References 13 publications

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“…Haem-deplete growth was performed in BHI broth supplemented with only 10 mg b-NAD ml 21 (haemdeplete BHI; hdBHI). H. influenzae were transformed to antibiotic resistance using a modification of the static aerobic method of Gromkova et al (1989) as previously described (Morton et al, 2004b).…”

Section: Methodsmentioning

confidence: 99%

The haem–haemopexin utilization gene cluster (hxuCBA) as a virulence factor of Haemophilus influenzae

et al. 2007

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Haemophilus influenzae has an absolute growth requirement for a porphyrin source, which can be supplied in vitro by haem, haemoglobin, or the haemoglobin-haptoglobin, haem-haemopexin and haem-albumin complexes. Utilization of the haem-haemopexin complex is known to be mediated by the products of the hxuCBA gene cluster. It was demonstrated that hxuC, but not hxuA or hxuB, is also essential for the utilization of haem from haem-albumin complexes. Mutants of the type b strain E1a lacking genes in the hxuCBA gene cluster were examined for their ability to cause bacteraemia in rat models of invasive disease. In 5-day-old rats, mutants in the hxuCBA genes yielded a significantly reduced bacteraemic titre compared to the wild-type strain. In addition, 5-day-old rats infected with the hxuCBA mutant strains exhibited significantly improved survival rates compared to those infected with the wild-type strain. Mutations in the haemoglobin/haemoglobinhaptoglobin-binding protein genes (hgps), either alone or in combination with the hxuCBA mutations, had no impact on virulence in 5-day-old rats. In 30-day-old rats infected with either the hxuCBA mutants or the wild-type strains, there was no significant difference in the ability to establish bacteraemia although bacterial titres were lower in rats infected with the hxuCBA mutants than in those infected with the wild-type strain. These age-related differences in the impact of mutations in the hxuCBA gene cluster may be related to changes in levels of host haem-binding proteins during development of the rat.

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Section: Methodsmentioning

confidence: 99%

The haem–haemopexin utilization gene cluster (hxuCBA) as a virulence factor of Haemophilus influenzae

et al. 2007

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“…H. influenzae strains HI689 and HI1717 were transformed to kanamycin resistance (25 g/ml with plasmid pDJM343 DNA using a modification of the static aerobic method of Gromkova et al (22) as previously described (38). Appropriate chromosomal insertions were confirmed by the size of a PCR product, and hxuC deletion mutants of strains HI689 and HI1717 were identified, phenotypically confirmed by growth characteristics in vitro, and designated strains HI1787 and HI1810, respectively.…”

Section: Methodsmentioning

confidence: 99%

Complex Role of Hemoglobin and Hemoglobin-Haptoglobin Binding Proteins in Haemophilus influenzae Virulence in the Infant Rat Model of Invasive Infection

Seale¹,

Morton²,

Whitby³

et al. 2006

Infect Immun

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Haemophilus influenzae requires an exogenous heme source for aerobic growth in vitro. Hemoglobin or hemoglobin-haptoglobin satisfies this requirement. Heme acquisition from hemoglobin-haptoglobin is mediated by proteins encoded by hgp genes. Both Hgps and additional proteins, including those encoded by the hxu operon, provide independent pathways for hemoglobin utilization. Recently we showed that deletion of the set of three hgp genes from a nontypeable strain (86-028NP) of H. influenzae attenuated virulence in the chinchilla otitis media model of noninvasive disease. The present study was undertaken to investigate the role of the hgp genes in virulence of the wild-type serotype b clinical isolate HI689 in the infant rat model of hematogenous meningitis, an established model of invasive disease requiring aerobic growth. Bacteremia of high titer and long duration (>14 days) and histopathologically confirmed meningitis occurred in >95% of infant rats challenged at 5 days of age with strain HI689. While mutations disrupting either the Hgp-or Hxu-mediated pathway of heme acquisition had no effect on virulence in infant rats, an isogenic mutant deficient for both pathways was unable to sustain bacteremia or produce meningitis. In contrast, mutations disrupting either pathway decreased the limited ability of H. influenzae to initiate and sustain bacteremia in weanling rats. Biochemical and growth studies also indicated that infant rat plasma contains multiple heme sources that change with age. Taken together, these data indicate that both the hgp genes and the hxuC gene are virulence determinants in the rat model of human invasive disease.

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“…DNA concentration was determined by measuring DNA transformation. Competence was induced by the static aerobic procedure (Gromkova & Goodgal, 1979;Gromkova et al, 1989b). For the transformation assay, 0-1 ml purified DNA at a saturating concentration of 1 pg ml-l was added to 0.8ml BHI broth supplemented with 1 mM-MgSO,.…”

Section: Methodsmentioning

confidence: 99%

Plasmid-mediated NAD independence in Haemophilus parainfluenzae

Windsor¹,

Gromkova²,

Koornhof³

1991

Journal of General Microbiology

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The location of the genes coding for NAD independence in four unusual clinical isolates of Haemophilus puruinfluenzae was determined by transferring these genes to plasmid-free Haemophilus influenza Rd by transformation and analysing transformants for the presence of plasmids by agarose gel electrophoresis. All NADindependent transformants were found to carry a single plasmid species. The plasmids, originally harboured by the four H. puruinfluenzue isolates recovered from unrelated sources, were of the same size (5.25 kb). Spontaneous reversion to NAD dependence occurred with a low frequency (0.1 to 0.2 % of the progeny of a single clone) in both H. puruinfluenzae and H. influenzae Rd. The revertants had lost this small plasmid. Mitomycin C exhibited a plasmid 'curing' effect with a frequency of 'curing' of between 1 and 6% of the surviving clones. It was concluded that the genes conferring NAD independence were located on the small 5-25 kb plasmid.

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Induction of competence in nonencapsulated and encapsulated strains ofHaemophilus influenzae

Cited by 15 publications

References 13 publications

The haem–haemopexin utilization gene cluster (hxuCBA) as a virulence factor of Haemophilus influenzae

The haem–haemopexin utilization gene cluster (hxuCBA) as a virulence factor of Haemophilus influenzae

Complex Role of Hemoglobin and Hemoglobin-Haptoglobin Binding Proteins in Haemophilus influenzae Virulence in the Infant Rat Model of Invasive Infection

Plasmid-mediated NAD independence in Haemophilus parainfluenzae

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