Molecular cloning and characterization of the nontypeable Haemophilus influenzae 2019 rfaE gene required for lipopolysaccharide biosynthesis

The lipooligosaccharide (LOS) of nontypeable Haemophilus influenzae (NTHi) is an important factor in pathogenesis and virulence. In an attempt to elucidate the genes involved in LOS biosynthesis, we have cloned the rfaE gene from NTHi 2019 by complementing a Salmonella typhimurium rfaE mutant strain with an NTHi 2019 plasmid library. The rfaE mutant synthesizes lipopolysaccharide (LPS) lacking heptose, and the rfaE gene is postulated to be involved in ADP-heptose synthesis. Retransformation with the plasmid containing 4 kb of NTHi DNA isolated from a reconstituted mutant into rfaE mutants gave wild-type LPS phenotypes. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis confirmed the conversion of the rfaE mutant LPS to a wild-type LPS phenotype. Sequence analysis of a 2.4-kb BglII fragment revealed two open reading frames. One open reading frame encodes the RfaE protein with a molecular weight of 37.6 kDa, which was confirmed by in vitro transcription and translation, and the other encodes a polypeptide highly homologous to the Escherichia coli HtrB protein. These two genes are transcribed from the same promoter region into opposite directions. Primer extension analysis of the rfaE gene revealed a single transcription start site at 37 bp upstream of the predicted translation start site. The upstream promoter region contained a sequence (TA AAAT) homologous to the -10 region of the bacterial sigma 70-dependent promoters at an appropriate distance (7 bp), but not sequence resembling the consensus sequence of the -35 region was found. These studies demonstrate the ability to use complementation of defined LPS defects in members of the family Enterobacteriaceae to identify LOS synthesis genes in NTHi.

Adhesion of nontypeable Haemophilus influenzae from blood and sputum to human tracheobronchial mucins and lactoferrin

Nontypeable Haemophilus influenzae strains are the most common pathogens encountered in patients with chronic bronchitis. These organisms chronically colonize the airways of patients and occasionally cause bacteremia. Nontypeable H. influenzae strains have been demonstrated microscopically to bind to mucus, but quantitative studies of adhesion have not been published to date. We have therefore developed a reproducible microtiter plate assay to study mucin binding and have examined the adhesion of sputum and blood strains of nontypeable H. influenzae. The assay is similar to that described for Pseudomonas aeruginosa (S. Vishwanath and R. Ramphal, Infect. Immun. 45:197-202, 1984), but notably 2% Tween 20 is used to desorb bacteria from the wells to quantitate bacterial binding. Using a standard strain, we have established that 1 h of incubation is optimum with an inoculum of < or = 5 x 10(8) CFU/ml. The standard strain binds to bronchitic and cystic fibrosis mucins equally well but binds less to bronchiectasis mucins. It does not bind to bovine serum albumin or fetuin. We have also examined the levels of adhesion of freshly isolated sputum and bacteremia strains and find very significant differences in adhesion. Blood strains bound six to seven times less than sputum strains ([13.8 +/- 7] x 10(2) per well versus [102 +/- 43] x 10(2); P < 0.001). Studies with adhesion to lactoferrin, another glycosylated protein, revealed variable binding of respiratory strains but marked binding of blood strains compared with mucin. An isogenic pair of respiratory and blood isolates was examined by electron microscopy but did not show surface differences. We speculate that bacteremic strains studied may have masked, lost, or downregulated adhesin production to allow them to escape from mucins or upregulated adhesins for lactoferrin to invade the bloodstream.

Neonatal infection due to Haemophilus influenzae biotype IV

Neonatal infection due to Haemophilus influenzae has several clinical similarities to infection by the more common Streptococcus agalactiae (Strep group B). A high frequency of H. influenzae biotype IV in association with genital, maternal and neonatal infections has been reported in the literature, suggesting this biotype has an affinity for the female genital tract. Cefotaxime should be considered as part of the treatment regimen when this organism is suspected because of the emerging resistance of H. influenzae to ampicillin. We present a case of H. influenzae biotype IV infection in a premature (32 weeks) neonate.

Activation of the neutrophil bactericidal activity for nontypable Haemophilus influenzae by tumor necrosis factor and lymphotoxin

Previous studies have suggested that, in vivo, activated T lymphocytes and neutrophils are important in immunity to nontypable Haemophilus influenzae. We now extend this work by showing that neutrophils pretreated with products of activated T lymphocytes or activated macrophages show significantly enhanced killing of nontypable H. influenzae. Lymphotoxin, a product of activated T lymphocytes, significantly enhanced the neutrophil-mediated killing of nontypable H. influenzae, and tumor necrosis factor, produced by activated T lymphocytes as well as macrophages stimulated by activated T lymphocytes, also significantly increased the bactericidal activity of neutrophils. These cytokine-induced effects were seen with short pretreatment times of neutrophils and were maximal by 30 min. The killing of H. influenzae by neutrophils required the presence of heat-labile opsonins. In the absence of these opsonins, both tumor necrosis factor and lymphotoxin were unable to promote the killing of the bacteria by neutrophils. Furthermore, the results showed that tumor necrosis factor-primed neutrophils displayed significantly increased expression of CR3 and CR4 that was associated with increased phagocytosis of complement-opsonized nontypable H. influenzae. These cytokines may play an important role in immunity toward nontypable H. influenzae by stimulating neutrophil bactericidal activity.

Region II of the Haemophilus influenzae type be capsulation locus is involved in serotype-specific polysaccharide synthesis

The central (serotype-specific) Region II of the Haemophilus influenzae Type b capsulation locus cap is 8.3 kb long and contains a cluster of four genes. We show that these genes, designated orf1 to orf4, are involved in the biosynthetic steps required for the formation of the Type b capsular polysaccharide and that orf1 probably encodes a CDP-ribitolpyrophosphorylase. We present evidence that growth of polysaccharide chains takes place through the alternating addition of single sugar nucleotides.

Invasive Haemophilus influenzae disease: epidemiology and clinical spectrum before large-scale H. influenzae type b vaccination

In a prospective study between January 1987 and December 1992, 103 patients with invasive Haemophilus influenzae (Hi) infection were identified in a well-defined population before large-scale Haemophilus influenzae type b (Hib) vaccination was introduced. The incidence (case/100,000/year) of invasive Hi infection was 5.9 for the whole population, 55 for children 0-4 years old and as high as 2.8 for adults. Hib was the predominant cause of the infection (83 cases) in children but, in adults, 13/39 (30%) cases were caused by non-typable Hi and 6/39 (19%) by Hi serotype f. Three patients (3%) died and 6 (5.8%) suffered a permanent sequel from the infection. All patients with such a sequel had invasive Hib infection. No significant difference between patients 0-6 years old and matched controls regarding the frequency of subnormal serum levels of immunoglobulins was found.

Hemophilus influenzae and Streptococcus pneumoniae as causative agents of pneumonia in Egyptian preschool children: analysis and serotyping of Hemophilus isolates from hospital patients in Cairo, 1991-93

The Hemophilus influenzae blood culture and nasopharyngeal isolates, collected during a limited Surveillance of Antimicrobial Resistance in 1991-1993 from 1,635 Egyptian children under 5 years of age, presenting with pneumonia to Embaba and Abbassia Fever Hospitals, were serotyped. The 8 blood culture isolates confirmed H. influenzae to be responsible for 0.5% of the cases of pneumonia, versus 50 Streptococcus pneumoniae blood culture isolates from the same population that confirmed it responsible for 3.1% of the cases. The invasive Hemophilus strains were exclusively isolated from infants below 1 year, from one hospital (Embaba), on one winter season (January to March, 1992). On serotyping, 50% of the blood culture isolates were found to be non-b by latex agglutination. Some 297 nasopharyngeal isolates from cases of pneumonia were also serotyped and 45% were found to be non-b, thus confirming the invasive strains findings. Furthermore, the typing results from ARI-free controls nasopharyngeal isolates--though limited--were consistent with the findings and showed a 43% proportion of non-b. These findings put a question mark on the benefit of a large scale use of the available H. influenzae type b polysaccharide and conjugated vaccines in Egypt. But before interpreting out data in terms of vaccine needs, more specifically designed epidemiological studies need to be conducted to assess the role of H. influenzae as a pathogen in Egypt.

Characterization of Haemophilus influenzae isolates from the respiratory tract of patients with primary antibody deficiencies: evidence for persistent colonizations

A total of 117 consecutive patients with primary antibody deficiencies were followed for up to 5 years with regard to acute respiratory tract infections. Nontypeable Haemophilus influenzae (NTHI) was the sole pathogen in 61% (202/330) of the samples from which a potential pathogen was recovered. Common variable immunodeficiency (CVI) was the most prevalent condition (27/39 patients) in the group where H. influenzae was isolated. In patients where H. influenzae was not found only 9/78 patients had CVI. 49 of these 78 patients had isolated IgG3 or IgA deficiency. Both of these entities seemed to be associated with a lower prevalence of NTHI infections. 13 of 18 patients with at least 2 isolates of NTHI were colonized with the same strain from 3 to 43 months as shown by total genomic DNA-fingerprinting. Recurrent symptomatic infections occurred in these patients despite substitution therapy with gammaglobulins and repeated antibiotic treatments. All but 2 of the 224 H. influenzae isolates were beta-lactamase negative and sensitive to ampicillin. The use of 10 lipopolysaccharide-specific monoclonal antibodies in a whole cell ELISA showed that the LPS-epitopes on the 224 H. influenzae isolates from the hypogammaglobulinemic group were very similar to 499 NTHI isolates from immunocompetent patients with respiratory infections. One may therefore conclude that i) patients with CVI, were prone to be permanently colonized with NTHI, and ii) the colonizing bacteria were ordinary strains showing the same LPS-phenotypes as those strains that cause acute respiratory tract infections in immunocompetent individuals.

Antimicrobial resistance in Haemophilus influenzae isolated from blood, cerebrospinal fluid, middle ear fluid and throat samples of children. A nationwide study in Finland in 1988-1990

A nation-wide survey of the prevalence of antimicrobial resistance in Haemophilus influenzae was conducted on isolates collected in 1988-90 from middle ear fluid (MEF), blood, or cerebrospinal fluid (CSF) in infected children or throat samples of healthy children. Altogether 885 strains were examined regarding capsular type b, beta-lactamase production and the minimal inhibitory concentration (MIC) of ampicillin, cefaclor, erythromycin, tetracycline, chloramphenicol, trimethoprim and trimethoprim-sulfamethoxazole for these strains was determined by the agar dilution method. 99% (578/585) of MEF isolates, 93% (112/121) of throat isolates, but only 6% (10/179) of blood/CSF isolates were not of type b (Hib). The rate of beta-lactamase production was 11.4% among Hib strains, 8.0% among non-type b MEF isolates, and 4.5% among non-type b throat isolates. No increase in the prevalence of beta-lactamase production in H. influenzae has taken place in Finland since the early 1980s. Resistance to ampicillin among strains that lacked beta-lactamase activity was rare (0.2%). Of the non-type b MEF and throat isolates, 5.9% and 2.7%, respectively, were resistant to trimethoprim and 3.6% and 2.7%, respectively, to trimethoprim-sulfamethoxazole. Resistance to other drugs was rare (< 2%) in all isolate groups.

Conservation of immune responses to proteins isolated by preparative polyacrylamide gel electrophoresis from the outer membrane of nontypeable Haemophilus influenzae

Outer membrane proteins P2, P4, and P6 and two with molecular masses of 26 and 28 kDa have been purified from a strain of nontypeable Haemophilus influenzae by a preparative form of polyacrylamide gel electrophoresis (PAGE). Outer membrane protein P6, with a molecular mass of 16 kDa (determined by sodium dodecyl sulfate [SDS]-PAGE) was purified by both native PAGE and SDS-PAGE from three strains of nontypeable H. influenzae and one strain of type b H. influenzae. The same conditions were required for purification from each strain. The suitability of proteins isolated by these methods was assessed by studying the immune response of rats immunized with P6 in incomplete Freund's adjuvant into the Peyer's patches. P6 purified by either native PAGE or SDS-PAGE did not differ significantly from P6 purified by gel filtration and anion-exchange chromatography in the ability to enhance pulmonary clearance of live bacteria. This study also investigated the effects of SDS on P2 immunological responses in vivo and the effects of the reagents Zwittergent and sodium lauryl sarcosinate on outer membrane protein lymphocyte-proliferative responses in vitro. It was found that the presence of SDS in the immunization emulsion enhanced the antigen-specific cell-mediated response but suppressed the antigen-specific antibody responses. The presence of residual traces of Zwittergent in an outer membrane protein preparation inhibited antigen-specific cell-mediated proliferation, whereas extraction of outer membrane proteins with sodium lauryl sarcosinate did not inhibit antigen-specific proliferation. These results demonstrate that preparative PAGE is a suitable method for the purification of proteins from the outer membrane of H. influenzae required for investigation of their immunological significance as vaccine candidates and that traces of reagents used during protein purification may play an important role in determining the success of in vivo and in vitro studies.

Serotypes and antimicrobial susceptibility of Haemophilus influenzae

During a one year prospective study of Haemophilus influenzae infections in patients treated in hospitals in the metropolitan area of Cape Town. H. influenzae type b accounted for 81.7% of 126 invasive isolates, whereas 86.1% of the 280 non-invasive isolates were non-typeable. Ampicillin resistance was detected among 10.8% of strains of which all but one produced beta-lactamase. All strains were susceptible to cefotaxime as were more than 95% to chloramphenicol, rifampicin, tetracycline but 20.4% were resistant to co-trimoxazole and 87.2% to erythromycin.

Development of a ribotyping scheme for Haemophilus influenzae type b

Ribotyping and outer-membrane protein subtyping were used to characterise 283 consecutive isolates of Haemophilus influenzae type b. These isolates were obtained primarily from patients with invasive disease in the UK and were received by the Public Health Laboratory Service Haemophilus Reference Laboratory prior to the implementation of Haemophilus influenzae serotype b vaccine in the UK. A subtyping scheme using the ribotyping method is suggested. Twenty-two ribotypes are described, 14 of which were found amongst the 283 clinical isolates characterised in this study. In contrast, only four outer-membrane protein subtypes were found amongst the 283 isolates. The ribotyping profiles were further used to estimate the relatedness of isolates. The resulting dendrogram suggested a population genetic structure different from that previously described for Haemophilus influenzae type b using multi-locus enzyme electrophoresis. This study shows the value of ribotyping as a subtyping method for epidemiological studies of Haemophilus influenzae type b. However, the further use of ribotyping for population genetic structure analysis of Haemophilus influenzae type b may be misleading and therefore inappropriate.

Outer membrane protein profiling to distinguish between Haemophilus aegyptius and non-capsulate Haemophilus influenzae biotype III

Outer membrane protein profiling was used to assist in determining the identity of an isolate of Haemophilus spp. that was presumptively identified as non-capsulate Haemophilus influenzae biotype III. The possibility that this strain was in fact Haemophilus aegyptius was queried because of clinical information and the source of the isolate. Sodium dodecyl-sulphate polyacrylamide gel electrophoresis was used to establish the identity of the isolate as non-capsulate H. influenzae biotype III and no H. aegyptius. Generally, protein profiling compared very favourably with other standard tests for identifying H. aegyptius: the method was easily and rapidly performed and gave an unequivocal result.

Antibiotic susceptibility of 206 Haemophilus influenzae isolates collected from children in central Italy

Susceptibility of 206 H. influenzae isolates was evaluated by disk diffusion method for 11 antimicrobial agents. No isolates were found to be resistant to third-generation cephalosporins, amoxicillin+clavulanic acid, gentamicin and ciprofloxacin. Four untypable isolates (1.9%) were beta-lactamase producing ampicillin-resistant; one of these was also resistant to chloramphenicol. The rate of resistance against rifampin was 0.5 percent.

Haemophilus influenzae epididymo-orchitis and bacteremia in a man infected with the human immunodeficiency virus

Haemophilus influenzae is a major bacterial pathogen in patients infected with the human immunodeficiency virus (HIV), although most infections with this organism occur in the respiratory tract. We describe an adult with HIV infection who presented with epididymo-orchitis due to H. influenzae. Eleven prior cases of H. influenzae epididymo-orchitis have been published, but all of these cases occurred in pediatric patients. Little is known about the prevalence of genitourinary tract infections caused by H. influenzae among adults. H. influenzae is a relatively rare cause of bacteremia in adults, but the frequency of H. influenzae bacteremia has been increasing among the HIV-positive population.

PCR for capsular typing of Haemophilus influenzae

A PCR method for the unequivocal assignment of Haemophilus influenzae capsular type (types a to f) was developed. PCR primers were designed from capsule type-specific DNA sequences cloned from the capsular gene cluster of each of the six capsular types. PCR product was amplified only from the capsular type for which the primers were designed. Product was confirmed by using either an internal oligonucleotide or restriction endonuclease digestion. A total of 172 H. influenzae strains of known capsular type (determined genetically) comprising all capsular types and noncapsulate strains were tested by PCR capsular typing. In all cases the PCR capsular type corresponded to the capsular genotype determined by restriction fragment length polymorphism analysis of the cap region. When used in conjunction with PCR primers derived from the capsular gene bexA, capsulate, noncapsulate, and capsule-deficient type b mutant strains could be differentiated. PCR capsular typing overcomes the problems of cross-reaction and autoagglutination associated with the serotyping of H. influenzae strains. The rapid and unequivocal capsular typing method that is described will be particularly important for typing invasive H. influenzae strains isolated from recipients of H. influenzae type b vaccine.

Evaluation of antimicrobial activities of clarithromycin and 14-hydroxyclarithromycin against three strains of Haemophilus influenzae by using an in vitro pharmacodynamic model

An in vitro pharmacodynamic model was used to simulate the in vivo pharmacokinetics of clarithromycin and 14-hydroxyclarithromycin in order to generate time-kill curves for three clinical isolates of Haemophilus influenzae (isolates 2019, 91-183, and 1746). Representative concentrations in serum or lung tissue and the pharmacokinetic parameters of clarithromycin and the 14-hydroxy metabolite, separately and in combination, were simulated for the time-kill studies. Amoxicillin-clavulanic acid was used as a control drug. The simulation of typical concentrations of the macrolides in serum in time-kill studies resulted in magnitudes of bacterial killing that were less than (for strains 2019 and 91-183, MICs = 4 mg/liter for clarithromycin and 14-hydroxy-clarithromycin) or equal to (for strain 1746, MIC = 1 mg/liter for clarithromycin and 14-hydroxyclarithromycin) those observed in amoxicillin-clavulanic acid studies. When typical concentrations in lung tissue were simulated, total log decreases in bacterial counts were greater than those achieved with typical concentrations in serum and, in the case of strain 1746, exceeded the magnitude observed with the control drug. In each case, the time to 3-log-unit killing was longer for the macrolides than for amoxicillin-clavulanic acid. Time-kill curve analyses demonstrated the presence of synergy (defined as a 2-log-unit decrease in the CFU per milliliter between the combination and the most active constituent at any time point) for the combination of clarithromycin and 14-hydroxyclarithromycin at simulated concentrations in serum for one strain of H. influenzae (isolate 91-183). Synergism is likely bacterial strain specific, and the presence of synergy may be dependent on the antibiotic concentrations that are tested. Evaluation of the kill curve kinetics in terms of bactericidal rate for the various starting concentrations of clarithromycin did not result in a clear demonstration of either concentration-dependent or concentration-independent bactericidal activity.

Neonatal osteomyelitis in Down's syndrome due to non-encapsulated Haemophilus influenzae

A case of neonatal osteomyelitis in a baby with Down's syndrome is described. The causative organism was a non-encapsulated Haemophilus influenzae biotype I, which was isolated from pus at the site of infection. This organism has not previously been reported as a cause of neonatal osteomyelitis.

Analysis by pulsed-field gel electrophoresis of insertion mutations in the transferrin-binding system of Haemophilus influenzae type b

A mutagenesis system involving the insertion of a non-transposable antibiotic resistance gene cassette was used to generate stable mutations in the chromosome of Haemophilus influenzae type b strain Eagan. The mutations generated were shown by pulsed-field gel electrophoresis (PFGE) to have unique SmaI fingerprint patterns and to be located randomly on the chromosome. Of 700 insertion mutants screened, 29 had stable insertions resulting in constitutive expression of transferrin-binding proteins (TBPs). The high proportion of such mutants indicated that numerous regulatory loci could influence the expression of this phenotype. Five such regulatory mutations were analysed in detail by PFGE and DNA hybridisation and were shown to be located at five different chromosomal loci, although three of the five loci were located on the same 330-kb SmaI fragment of the wild-type strain Eagan chromosome. This fragment also contains several important virulence determinants, including the capb locus, and one of the five constitutive mutants had concomitantly lost the ability to synthesise a type-b capsule. No DNA homology was demonstrated between H. influenzae chromosomal fragments separated by PFGE and DNA probes for the TBPs from Neisseria meningitidis, but the possibility of shared regulatory mechanisms controlling the expression of TBPs in these two species remains to be investigated.

[The features of Haemophilus influenza and Streptococcus pneumoniae carriage and the comparative characteristics of strains isolated from healthy children and from patients with acute and chronic respiratory infections]

The biological properties (serotypes, biotypes and adhesive activity) of 839 H.influenzae strains isolated from healthy children and from patients with acute and chronic respiratory infections, as well as the serotype composition of 739 S.pneumoniae isolated from the same groups of children, were studied. The occurrence of H.influenzae carriership among healthy children varied between 13% and 78%, decreasing among older children. In 98% of cases the respiratory tract of healthy children was colonized by noncapsular forms of H.influenzae. The isolation frequency of pneumococci in healthy children was 16%, but during the period of 2 years 45% of children were found to be the transitory carriers of this infective agent. The persistence of H.influenzae and S.pneumoniae with the same biological properties lasted for 1-4 months. Repeated infections were caused, as a rule, by bacteria with other properties. S.pneumoniae persisting in healthy children and causing a chronic bronchopulmonary process had no differences in their serological composition (19, 6, 3). At the same time in acute pneumonia, complicated by pleuritis and pneumonia destruction, pneumococci of serotypes 1, 3, 5 and 14 were more frequently isolated. H.influenzae isolated from healthy children and from patients with chronic pneumonia had little difference in the occurrence of their capsular variants, but in the biotype composition of H.influenzae isolated from chronic pneumonia patients biotype 1 occurred more frequently.

The fimbrial gene cluster of Haemophilus influenzae type b

Haemophilus influenzae infections are preceded by airway colonization, a process facilitated by fimbriae. Here, we identified the complete fimbrial gene cluster of H. influenzae type b. HifA forms the major subunit. HifB, a periplasmic chaperone, and HifC, an outer membrane usher, are typical assembly genes; their inactivation abolished fimbriae formation. HifD and HifE are putative minor subunits, both participating in fimbriae biogenesis. Inactivation of either one drastically reduced fimbriae expression. HifD represents a novel type of fimbrial subunit with lipoprotein characteristics, pointing to a membrane-associated function of HifD. Transcription of all fimbrial genes is coregulated through two clustered promoters. The flanking of the fimbrial gene cluster by repetitive extragenic palindromic sequences together with a partial duplication of an adjacent unrelated operon indicated that the cluster was once inserted in the H. influenzae genome as a mobile virulence unit.

Genomic DNA fingerprinting of clinical Haemophilus influenzae isolates by polymerase chain reaction amplification: comparison with major outer-membrane protein and restriction fragment length polymorphism analysis

Non-capsulate strains of Haemophilus influenzae were genotyped by analysis of variable DNA segments obtained by amplification of genomic DNA with the polymerase chain reaction (PCR fingerprinting). Discrete fragments of 100-2000 bp were obtained. The reproducibility of the procedure was assessed by comparing: (i) the fingerprints of 16 colonies of a single H. influenzae strain; (ii) isolates obtained from individual sputum samples (a total of 57 H. influenzae isolates from three cystic fibrosis patients); and (iii) 17 isolates collected during an outbreak of H. influenzae infection in a local pulmonary rehabilitation centre. The discriminatory power of the method was demonstrated by showing that the PCR fingerprints of eight unrelated H. influenzae strains from sputum samples of patients with chronic obstructive pulmonary disease (COPD) and 32 strains from cystic fibrosis patients were all different. These 40 isolates also differed with respect to their restriction fragment length polymorphisms (RFLP) and major outer-membrane protein (MOMP) composition. Twelve MOMP antigenic strain variants from sputum samples of five COPD patients had identical PCR fingerprints and RFLPs. It was concluded that PCR fingerprinting is a reliable and reproducible method for genotyping non-capsulate strains of H. influenzae. The discriminatory power of PCR fingerprinting was similar to that of RFLP analysis, but the results of PCR fingerprinting were easier to interpret.