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Query: UMLS:C0348321 (Haemophilus)
 15,372 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Haemophilus strains usually identified as Haemophilus influenzae biotype IV belonging to a cryptic genospecies are responsible for genital and neonatal infections. As a first approach to identifying the bacterial factors involved in the pathogenesis of these unusual diseases, we studied the piliation, adherence, and invasion properties of 17 strains assigned to this cryptic genospecies. Twelve strains spontaneously displayed abundant peritrichous piliation, and two strains expressed peritrichous pili after enrichment procedures. For virtually all strains, piliation correlated with adhesion to cultured HeLa cells of genital origin and to a lesser extent with adhesion to HEp-2 cells of laryngeal origin. A variation in the adherence properties of the various strains was observed: all piliated strains except one adhered to 50 to 100% of HeLa cells, with a mean number of bacteria per cell varying from 4 to 50. Adherence was not dependent on the state of growth for most strains, was more pronounced with HeLa cells than with HEp-2 cells for 10 of the 12 highly adherent strains, was time and inoculum dependent, and was not followed by significant invasion of cells. Most of the strains belonging to this unusual Haemophilus clone possess adhesins that do not recognize erythrocyte receptors, since agglutination of human erythrocytes was observed with only 3 of the 14 piliated strains.
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PMID:Adherence to human cells of a cryptic Haemophilus genospecies responsible for genital and neonatal infections. 810 93

Nontypable strains of Haemophilus influenzae are well-known causes of maternal and neonatal infections. Using DNA-DNA hybridization techniques, some of these strains have been shown to belong to a cryptic genospecies of Haemophilus, which is distantly related to Haemophilus influenzae and Haemophilus hemolyticus. This report describes the first case of sepsis and chorioamnionitis due to Haemophilus influenzae biotype I, which was identified using the RapIDNH system and then confirmed by multilocus enzyme electrophoresis to belong to this cryptic genospecies of Haemophilus. The electromorph type 92 of the isolate was consistent with that of biotype I of the cryptic genospecies.
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PMID:Bacteremia and chorioamnionitis due to cryptic genospecies of Haemophilus Influenzae biotype I. 868 86

Previous genetic analysis of Haemophilus influenzae strains isolated from genital and neonatal infections identified a group of biotype IV that constitutes a cryptic genospecies only distantly related to H. influenzae and H. Haemolyticus. Small-subunit rRNA genes of two representative strains of this genital Haemophilus genospecies (strains 16N and 2406) were sequenced. The analysis indicated that these strains form a monophyletic unit with H. haemolyticus and H. influenzae biogroups Influenzae and Aegyptius and are more closely related to H. haemolyticus than to H. influenzae biogroups Influenzae and Aegyptius. 16S rRNA gene sequences were used to formulate primers for PCR-based identification of cryptic genital Haemophilus organisms. A 242-bp fragment was amplified from strains belonging to the genital Haemophilus genospecies but not from strains of 12 other Haemophilus species, including strains of H. influenzae biotype IV sensu stricto.
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PMID:Genetic identification of cryptic genospecies of Haemophilus causing urogenital and neonatal infections by PCR using specific primers targeting genes coding for 16S rRNA. 873 84

The Gram-positive transposon Tn916 was introduced into two strains of Haemophilus paragallinarum by electroporation of the suicide plasmid pAM120 (pGL101::Tn916). Tetracycline resistant mutants of H. paragallinarum strains Tw-1 and 221 were recovered at frequencies of 2.1 x 10(-6) and 4.5 x 10(-7) per viable cell electroporated, respectively. Tn916 generates stable single insertions within different sites of the H. paragallinarum chromosome. One Tw-1::Tn916 mutant had the Tn916 insertion in the cryptic plasmid p250. This study indicates the potential use of Tn916 as a genetic tool for insertional mutagenesis of H. paragallinarum.
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PMID:Transposon mutagenesis of Haemophilus paragallinarum with Tn916. 905 24

In an attempt to identify and characterize components of a heme uptake system of Haemophilus somnus, an Escherichia coli cosmid library of H. somnus genomic DNA was screened for the ability to bind hemin (Hmb+). The Hmb+ phenotype was associated with a 7,814-bp HindIII fragment of H. somnus DNA that was subcloned and sequenced. Thirteen open reading frames (orfs) were identified, all transcribed in one direction, and transposon mutagenesis identified orf7 as the gene associated with the Hmb+ phenotype. Orf7 (178 amino acids) has extensive homology with the lysozymes of bacteriophages P-A2, P21, P22, PZA, phi-29, phi-vML3, T4, or HP1. The orf7 gene complemented the lytic function of the K gene of phage P2 and the R gene of phage lambda. A lysozyme assay using supernatants from whole-cell lysates of E. coli cultures harboring plasmid pRAP501 or pGCH2 (both of which express the orf7 gene product) exhibited significant levels of lysozyme activity. The orf6 gene upstream of orf7 has the dual start motif common to the holins encoded by lambdoid S genes, and the orf6 gene product has significant homology to the holins of phages HP1 and P21. When expressed from a tac promoter, the orf6 gene product caused immediate cell death without lysis, while cultures expressing the orf7 gene product grew at normal rates but lysed immediately after the addition of chloroform. Based on this data, we concluded that the Hmb+ phenotype was an artifact resulting from the expression of cloned lysis genes which were detrimental to the E. coli host. The DNA flanking the cloned lysis genes contains orfs that are similar to structural and DNA packaging genes of phage P2. Polyclonal antiserum against Orf2, which is homologous to the major capsid precursor protein (gpN) of phage P2, detected a 40,000-M(r) protein expressed from pRAP401 but did not detect Orf2 in H. somnus, lysates. The phage-like DNA was detected in the serum-susceptible preputial strains HS-124P and HS-127P but was absent from the serum-resistant preputial strains HS-20P and HS-22P. Elucidation of a potential role for this cryptic prophage in the H. somnus life cycle requires more study.
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PMID:Cloning and characterization of bacteriophage-like DNA from Haemophilus somnus homologous to phages P2 and HP1. 906 31

Nineteen isolates belonging to a cryptic genospecies of Haemophilus (referred to here as genital strains) isolated from genital tract infections (6 strains) and from neonatal infections (13 strains) were studied for fimbrial genes. Sixteen strains exhibit peritrichous fimbriae observed by electron microscopy. By PCR with primers corresponding to the extreme ends of the Haemophilus influenzae type b (Hib) hifA and hifD genes and Southern blotting, a hifA-like gene (named ghfA) and a hifD-like gene (named ghfD) were identified in 6 of the 19 strains. Five of these six strains were from the genital tracts of adults, and one was from a neonate. For each gene, the nucleotide sequence was identical for the six strains. A hifE-like gene (named ghfE) was amplified from only one of the 19 genital strains of Haemophilus, but the ghfE probe gave a signal in Southern hybridization with the five other strains positive for ghfA and ghfD. Therefore, these strains may carry a ghfE-like gene. The Hib fimbrial gene cluster is located between the purE and pepN genes as previously described. For the 13 genital Haemophilus strains that lack fimbrial genes, this region corresponds to a noncoding sequence. Another major fimbrial gene designated the fimbrin gene was previously identified in a nontypeable H. influenzae strain. A fimbrin-like gene was identified for all of our 19 genital strains. This gene is similar to the ompP5 gene of many Haemophilus strains. Therefore, other, unidentified genes may explain the piliation observed in electron microscopy on genital Haemophilus strains which do not possess LKP-like fimbrial genes. Fimbrial genes were significantly associated with strains isolated from the genital tract. They may confer on the strain the ability to survive in the genital tract.
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PMID:Nucleotide sequences of genes coding for fimbrial proteins in a cryptic genospecies of Haemophilus spp. isolated from neonatal and genital tract infections. 986 89

We report DNA and predicted protein sequence similarities, implying homology, among genes of double-stranded DNA (dsDNA) bacteriophages and prophages spanning a broad phylogenetic range of host bacteria. The sequence matches reported here establish genetic connections, not always direct, among the lambdoid phages of Escherichia coli, phage phiC31 of Streptomyces, phages of Mycobacterium, a previously unrecognized cryptic prophage, phiflu, in the Haemophilus influenzae genome, and two small prophage-like elements, phiRv1 and phiRv2, in the genome of Mycobacterium tuberculosis. The results imply that these phage genes, and very possibly all of the dsDNA tailed phages, share common ancestry. We propose a model for the genetic structure and dynamics of the global phage population in which all dsDNA phage genomes are mosaics with access, by horizontal exchange, to a large common genetic pool but in which access to the gene pool is not uniform for all phage.
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PMID:Evolutionary relationships among diverse bacteriophages and prophages: all the world's a phage. 1005 17

Transposon mutagenesis in bacteria generally requires efficient delivery of a transposon suicide vector to allow the selection of relatively infrequent transposition events. We have developed an IS903-based transposon mutagenesis system for diverse gram-negative bacteria that is not limited by transfer efficiency. The transposon, IS903phikan, carries a cryptic kan gene, which can be expressed only after successful transposition. This allows the stable introduction of the transposon delivery vector into the host. Generation of insertion mutants is then limited only by the frequency of transposition. IS903phikan was placed on an IncQ plasmid vector with the transposase gene located outside the transposon and expressed from isopropyl-beta-D-thiogalactopyranoside (IPTG)-inducible promoters. After transposase induction, IS903phikan insertion mutants were readily selected in Escherichia coli by their resistance to kanamycin. We used IS903phikan to isolate three catalase-deficient mutants of the periodontal pathogen Actinobacillus actinomycetemcomitans from a library of random insertions. The mutants display increased sensitivity to hydrogen peroxide, and all have IS903phikan insertions within an open reading frame whose predicted product is closely related to other bacterial catalases. Nucleotide sequence analysis of the catalase gene (designated katA) and flanking intergenic regions also revealed several occurrences of an 11-bp sequence that is closely related to the core DNA uptake signal sequence for natural transformation of Haemophilus influenzae. Our results demonstrate the utility of the IS903phikan mutagenesis system for the study of A. actinomycetemcomitans. Because IS903phikan is carried on a mobilizable, broad-host-range IncQ plasmid, this system is potentially useful in a variety of bacterial species.
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PMID:Direct selection of IS903 transposon insertions by use of a broad-host-range vector: isolation of catalase-deficient mutants of Actinobacillus actinomycetemcomitans. 1057 34

Haemophilus spp. were isolated from the amniotic fluid of eight of 110 consecutive women with preterm premature rupture of membranes (PROM) between 1992 and 1998. Isolates were nontypeable and classified according to biochemical test results as Haemophilus influenzae biotype I (n = 1), biotype II (n = 4), biotype III (n = 1) or biotype IV (n = 2). Primers recognizing specific sequences in the 16S rRNA of the cryptic genospecies of Haemophilus were employed to amplify the DNA of the eight isolates. One isolate classified as Haemophilus influenzae biotype II was confirmed as belonging to the genital cryptic species. Infectious morbidity occurred in five women and two newborns and was associated in most cases with biotype II.
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PMID:Role of Haemophilus influenzae in intra-amniotic infection in patients with preterm rupture of membranes. 1069 Dec 1

The distribution of large conjugative Haemophilus influenzae plasmids in the nasopharyngeal haemophili of a group of people and in a large collection of 541 H. influenzae type b (Hib) isolates was studied. A newly developed PCR-based assay was used to detect the plasmids. The target sequences were chosen from sequence analysis of part of p1056, a large multiresistance plasmid isolated from a clinical Hib isolate, 1056. Fifty-nine per cent of people were found to carry beta-lactamase-positive (beta-lac(+)), ampicillin-resistant (ampR) haemophili with detectable plasmid sequences. Of these, 83% were in Haemophilus parainfluenzae and 17% were in H. influenzae. In the collection of 541 Hib, antibiotic resistance [beta-lac(+)ampR, beta-lac(+)ampR plus tetracycline resistance (tetR) or tetR] was highly correlated with large plasmids. It was found that 2.3% of the isolates contained large cryptic plasmids (i.e. these isolates were susceptible to antibiotics). The distribution of plasmids between invasive and carried Hib did not differ significantly (25 of 245 and 23 of 276, respectively). Isolates with large plasmids occur at high frequency in the nasopharynx of the normal human population and consist of two populations in Hib, one associated with specific antibiotic resistance traits and the other cryptic. These plasmids do not appear to influence the invasiveness of Hib.
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PMID:Epidemiological studies of large resistance plasmids in Haemophilus. 1079 80


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