Identification of a second family of high-molecular-weight adhesion proteins expressed by non-typable Haemophilus influenzae

We previously reported that two surface-exposed high-molecular-weight proteins, HMW1 and HMW2, expressed by a prototypic strain of non-typable Haemophilus influenzae (NTHI), mediate attachment to human epithelial cells. These proteins are members of a family of highly immunogenic proteins common to 70-75% of NTHI strains. NTHI strains that lack HMW1/HMW2-like proteins remain capable of efficient attachment to cultured human epithelial cells, suggesting the existence of additional adhesion molecules. We reasoned that characterization of high-molecular-weight immunogenic proteins from an HMW1/HMW2-deficient strain might identify additional adhesion proteins. A genomic library was prepared in lambda EMBL3 with chromosomal DNA from non-typable Haemophilus strain 11, a strain that lacks HMW1/HMW2-like proteins. The library was screened immunologically with convalescent serum from a child naturally infected with strain 11, and phage clones expressing high-molecular-weight recombinant proteins were identified by Western blot analysis. One clone was identified that expressed a protein with an apparent molecular mass greater than 200 kDa. Transformation of non-adherent Escherichia coli strain DH5 alpha with plasmids containing the genetic locus encoding this protein gave rise to E. coli transformants that adhered avidly to Chang conjunctival cells. Subcloning and mutagenesis studies localized the DNA conferring the adherence phenotype to a 4.8 kbp fragment, and nucleotide sequence analysis further localized the gene encoding the adhesion protein to a 3.3 kbp open reading frame predicted to encode a protein of 114 kDa. The gene was designated hia for Haemophilus influenzae adhesin. Southern analysis revealed an hia homologue in 13 of 15 HMW1/HMW2-deficient non-typable H. influenzae strains. In contrast, the hia gene was not present in any of 23 non-typable H. influenzae strains which expressed HMW1/HMW2-like proteins. Identification of this second family of high-molecular-weight adhesion proteins suggests the possibility of developing vaccines based upon a combination of HMW1/HMW2-like proteins and Hia-like proteins which would be protective against disease caused by most or all non-typable H. influenzae.

Molecular characteristics of Haemophilus influenzae causing invasive disease during the period of vaccination in Switzerland: analysis of strains isolated between 1986 and 1993

The broad use of conjugated vaccines against Haemophilus influenzae type b may select for strains to which the polysaccharide vaccine does not provide immunity. We analyzed 392 consecutive H. influenzae isolates from Swiss children 0 to 16 years of age with invasive disease during the years 1986 to 1993. Bacterial strains were characterized by serotyping, capsular genotyping, outer membrane protein (OMP) subtyping, and ribotyping. Of 392 strains, 372 were serotype b, 1 was serotype a, 3 were serotype f, and 16 were nontypeable H. influenzae. After the introduction of Haemophilus conjugate vaccines in 1990, there was a relative increase of nontypeable strains from 3 to 6.6% (P = 0.27). Of the type b strains, 281 (75.5%) had the same OMP subtype and ribotype pattern. This clone predominated in the pre- and postvaccine periods. After the year 1990, the proportions of OMP subtype 1c and OMP subtype 3 tended to increase. Isolates from previously vaccinated (n = 10) and nonvaccinated patients did not differ in their subtype distributions. We conclude that the administration of conjugated vaccines decreased invasive disease caused by the most prevalent H. influenzae type b clone. However, further surveillance of circulating H. influenzae strains during the period of vaccination is indicated.

Outer membrane permeability of non-typable Haemophilus influenzae

The permeability to cephaloridine was studied in five Haemophilus influenzae strains (four non-typable and one type b) using the Zimmermann and Rosselet method. The beta-lactamase activity was due to a plasmid-encoded TEM-1 enzyme. High permeability coefficients were measured in all strains examined. No great differences in permeability coefficients were found, even between strains with marked differences in OMP electrophoretic profiles.

Invasive Haemophilus influenzae type b infection in a child with familial deficiency of the beta subunit of the eighth component of complement

A child who had had meningitis caused by Haemophilus influenzae type b, and then had meningococcal meningitis, was found to have familial deficiency of the beta subunit of the eighth component of complement. The child had not received the H. influenzae type b vaccine. If this deficiency is discovered, we recommend that family members be screened, regardless of their health status.

[Antimicrobial resistance in Haemophilus influenzae in the city of Havana, Cuba]

Fifty five Haemophilus influenzae strains were studied to determine their resistance to different antimicrobial drugs. They were isolated in Habana City, Cuba, during June 1992 to May 1993, from invasive and non invasive infections. An agar dilution method, according to NCCLS guidelines, was employed. We observed that 49%, 47.3% and 27.3% were resistant to ampicillin, tetracycline and chloramphenicol, respectively. beta-lactamase production was demonstrated in 22 strains (40%). There was neither resistance to ceftriaxone, cefotaxime nor rifampicin. 36.4% of the strains were multiresistant, being described 7 different resistance patterns. The rate of resistance to the drugs was substantially higher among serotype b than among non type b strains.

A virulent nonencapsulated Haemophilus influenzae

Nontypeable Haemophilus influenzae strain INT1 was isolated from the blood of a young child with clinical signs of meningitis following acute otitis media. No immunologic or anatomic predisposition of this child for invasive bacterial infection with an unusual organism was documented. Sensitive ELISA proved the absence of intra- or extracellular capsular polysaccharide production by INT1 and Southern blot analysis confirmed the lack of an intact capsulation (cap) gene locus within the chromosome. Nevertheless, INT1 established bacteremia and meningitis in infant and weanling rat models of invasive H. influenzae infection. High-molecular-weight DNA isolated from INT1 was shown to confer an invasive phenotype on transformation of a nonencapsulated, avirulent laboratory strain of H. influenzae. Together these findings imply the presence of one or more as-yet-undiscovered, noncapsular virulence factors of H. influenzae that are capable of mediating invasive disease and resistance to immunologic clearance.

Mutation of the htrB locus of Haemophilus influenzae nontypable strain 2019 is associated with modifications of lipid A and phosphorylation of the lipo-oligosaccharide

The HtrB protein was first identified in Escherichia coli as a protein required for cell viability at high temperature, but its expression was not regulated by temperature. We isolated an htrB homologue from non-typable Haemophilus influenzae strain (NTHi) 2019, which was able to functionally complement the E. coli htrB mutation. The promoter for the NTHi 2019 htrB gene overlaps the promoter for the rfaE gene, and the two genes are divergently transcribed. The deduced amino acid sequence of NTHi 2019 HtrB had 56% homology to E. coli HtrB. In vitro transcription-translation analysis confirmed production of a protein with an apparent molecular mass of 32-33 kDa. Primer extension analysis revealed that htrB was transcribed from a sigma 70-dependent consensus promoter and its expression was not affected by temperature. The expression of htrB and rfaE was 2.5-4 times higher in the NTHi htrB mutant B29 than in the parental strain. In order to study the function of the HtrB protein in Haemophilus, we generated two isogenic htrB mutants by shuttle mutagenesis using a mini-Tn3. The htrB mutants initially showed temperature sensitivity, but they lost the sensitivity after a few passages at 30 degrees C and were able to grow at 37 degrees C. They also showed hypersensitivity to deoxycholate and kanamycin, which persisted on passage. SDS-polyacrylamide gel electrophoresis analysis revealed that the lipo-oligosaccharide (LOS) isolated from these mutants migrated faster than the wild type LOS and its color changed from black to brown as has been described for E. coli htrB mutants. Immunoblotting analysis also showed that the LOS from the htrB mutants lost reactivity to a monoclonal antibody, 6E4, which binds to the wild type NTHi 2019 LOS. Electrospray ionization-mass spectrometry analysis of the O-deacylated LOS oligosaccharide indicated a modification of the core structure characterized in part by a net loss in phosphoethanolamine. Mass spectrometric analysis of the lipid A of the htrB mutant indicated a loss of one or both myristic acid substitutions. These data suggest that HtrB is a multifunctional protein and may play a controlling role in regulating cell responses to various environmental changes.

Multiple Haemophilus influenzae strains and strain variants coexist in the respiratory tract of patients with cystic fibrosis

To investigate the epidemiology of nontypeable Haemophilus influenzae in the respiratory tract of cystic fibrosis (CF) patients, H. influenzae isolates from sputum specimens of 40 CF patients were analyzed longitudinally for 2 years. The isolates were characterized by analysis of the major outer membrane protein (MOMP) patterns. MOMP variant H. influenzae strains were discriminated from distinct strains by randomly amplified polymorphic DNA analysis of genomic DNA. Multiple H. influenzae strains and MOMP variant strains were isolated from single sputum specimens of 29 patients. In 22 patients, a distinct H. influenzae strain persisted over time (median persistence, 8 months; range 2-24). In general, the appearance of MOMP variant strains did not coincide with the occurrence of exacerbations.

Experimental recurrent otitis media induced by Haemophilus influenzae: protection and serum antibodies

PURPOSE

To study whether acute otitis media caused by encapsulated or nontypeable Haemophilus influenzae confers cross-reactive protective immunity in an animal model system and to explore the possible involvement of various humoral specific antibodies in protection.

MATERIALS AND METHODS

Rats were intrabullarly challenged with H influenzae type b and two different nontypeable H influenzae strains. One month after the initial infection, the animals were rechallenged ipsilaterally or contralaterally with either a homologous or heterologous strain, and the susceptibility to reinfection was investigated by otomicroscopy.

RESULTS

The animals challenged and rechallenged with the type b strain were well-protected ipsilaterally and contralaterally, while the protection after homologous rechallenge with a nontypeable strain was partial in the ipsilateral ear and very poor in the contralateral ear. Middle ears previously infected with a nontypeable strain remained fully susceptible to infections with heterologous strains, but there was an indication of cross-protection in the animal groups where the first episode of acute otitis media was caused by type b and the second by a nontypeable strain. Using the Western blot technique and an enzyme linked immunosorbant assay, the serological response to different outer membrane proteins, especially protein D, of H influenzae during and after middle ear infection were investigated. The serological response from the type b infected animals were generally more distinct, while the antibody levels against protein D were lower in these groups compared with the groups infected with nontypeable strains.

CONCLUSIONS

These data indicate that H influenzae type-b-induced experimental otitis media results in a better protection than a nontypeable-induced, and H influenzae b confers a cross protection.

The emergence of Haemophilus influenzae types e and f as significant pathogens

Non-type b encapsulated Haemophilus influenzae meningitis (two cases due to H. influenzae type e, two due to H. influenzae type f) was diagnosed in four children in a 6-month period at the University of Virginia. H. influenzae type b was the most common cause of bacterial meningitis in the United States before the introduction of an effective vaccine, whereas the other five encapsulated serotypes of H. influenzae rarely caused invasive disease. The clinical features of non-type b H. influenzae meningitis and the therapy for this infection are the same as those for type b H. influenzae disease. We report these four cases to document an increase in infection due to non-type b serotypes of H. influenzae, and we postulate that this change may result from the well-documented decrease in H. influenzae type b oropharyngeal carriage and disease that has occurred because of universal vaccination for H. influenzae type b.

The elucidation of novel capsular genotypes of Haemophilus influenzae type b with the polymerase chain reaction

Molecular characterization is an important pre-requisite for post-vaccine studies of Haemophilus influenzae type b (Hib). Three capsular genotyping patterns, b(S), b(G) and b(V), have been described in the major phylogenetic lineage of Hib. However, in a recent series of prospective studies, three new hybridisation patterns were observed among 425 strains of Hib. Four pairs of polymerase chain reaction (PCR) primers were used to identify the capsular gene (cap) structure of these Hib strains. This showed that the strains possessed simple DNA re-arrangements. In two instances a change in restriction enzyme recognition site was the most likely cause of the new hybridisation pattern. The third strain possessed a cap b locus consisting of intact tandem repeats of cap b in a b(S) background. It was reasoned that a similar cap b locus would not be readily recognised by hybridisation in a b(G) background, and b(G) strains were therefore characterized by the PCR method. This showed one of 35 b(G) strains to possess a cap locus with intact tandem repeat copies of cap b. The novel capsular genotypes described here are rare, but can be detected rapidly and accurately by a combination of PCR and capsular genotyping hybridisation patterns.

Epidemiology of invasive Haemophilus influenzae infections in England and Wales in the pre-vaccination era (1990-2)

This survey defined the pattern of invasive Haemophilus influenzae infections during 1990-2 in six regions in England and Wales during the pre-vaccination era providing a baseline against which any changes in patterns of disease due to the introduction of the Haemophilus influenzae type b vaccination programme can be monitored. A total of 946 cases of invasive Haemophilus influenzae were recorded during the survey period of which almost 90% were due to type b and most of the remainder were non-typeable. Type b infections occurred predominantly in children less than 5 years of age (88%) with the highest attack rate in male infants in the 6-11 month age group. Diagnostic category varied with both age and serotype; meningitis was the commonest presentation overall but pneumonia and bacteraemia were more common in adults and non-typeable isolates. Mortality was highest in neonates and the elderly (over 65 years of age) who were more likely to have an underlying predisposing condition than older children and adults. Children under 5 years of age had a higher case fatality rate for non-typeable than for type b infections. Ampicillin resistance was 15% and there were no cefotaxime resistant type b isolates.

Antibody response of low birth weight infants to Haemophilus influenzae type b polyribosylribitol phosphate-outer membrane protein conjugate vaccine

OBJECTIVE

To evaluate the effectiveness in low birth weight (LBW) infants of the currently recommended immunization schedule for conjugated Haemophilus influenzae type b (HIB) vaccine.

METHODS

We quantified antibody responses in 36 preterm infants with a mean birth weight of 1060 g and a mean gestational age of 28 weeks. Infants were immunized with 0.5 mL of HIB vaccine at 2 and 4 months' postnatal age. Specific HIB antibodies were quantified on cord blood, immediately before each immunization and 2 months after the last immunization.

RESULTS

Even though the geometric mean titers increased significantly during the study period, they were still markedly lower than values reported in term infants. After the second immunization, only 24 infants (67%) attained antibody concentrations of more than 0.25 micrograms/mL, defined as seropositivity. Also, only 53% of infants achieved antibody concentrations of more than 1.0 micrograms/mL compared with 92% as reported in term infants. Stepwise logistic regression identified gestational age of 27 weeks or less and the amount of intravenous immunoglobulin received as the significant variables influencing the antibody response after the first immunization. The incidence of side effects was negligible.

CONCLUSIONS

We conclude that LBW infants, and especially those born at 27 or less weeks' gestation, do not respond as effectively to the HIB vaccine. We speculate that reevaluation of the current immunization schedule may be required for very LBW infants.

Turnover of nonencapsulated Haemophilus influenzae in the nasopharynges of otitis-prone children

Restriction enzyme analysis of total genomic DNA was applied to study the epidemiology of nontypeable Haemophilus influenzae (NTHI) isolated from the nasopharynges of children with recurrent acute otitis media (AOM). The turnover of strains, as judged from genetic fingerprinting of a total of 213 H. influenzae isolates collected prospectively during a 2-year study period from 38 children under 3 years of age, was examined in relation to episodes of AOM as well as to courses of antibiotic treatment. The children were selected if they had had at least one episode of AOM before 1 year of age and if more than two nasopharyngeal isolates of H. influenzae were recovered. The 213 H. influenzae isolates (90% NTHI) recovered corresponded to 128 different DNA fingerprints. Fifty-eight percent of the fingerprints were observed only once, whereas 42% appeared on two or more occasions in isolates from the same individual or in close relatives, i.e., brothers and sisters. Sixty-seven percent of these strains had a minimum colonization period of 2 months or less. Intermittent nasopharyngeal colonization periods longer than 5 months could be demonstrated for 13% of the strains. The present data suggest that intermittent colonization is due to endogenous reinfections. Genetically identical NTHI strains from unrelated individuals were never identified. As expected from the observation of a relatively high proportion of persistent colonizations, no correlation was found between episodes of AOM and the acquisition of new strains of H. influenzae, nor was any direct relation between antimicrobial therapy and the elimination of nasopharyngeal colonization with a particular strain of H. influenzae observed.

Clonal analysis of Haemophilus influenzae type b isolates in the United Kingdom

Strains of Haemophilus influenzae type b were collected as part of an epidemiological study of bacterial meningitis in the North East Thames Region (NETR) of England. Subclones of H. influenzae were identified by outer-membrane protein typing and multilocus enzyme electrophoresis. These were compared with subclones of H. influenzae type b isolated from elsewhere in the UK. The subclone ET 12.5/OMP 3L was identified in 68% of isolates from cases of meningitis from the NETR. In the isolates from elsewhere in the UK, this subclone was identified in 79% of sterile-site isolates and 91% of isolates from non-sterile sites. This subclone predominated in patients of different ages and from different ethnic groups, which suggests that non-Caucasians are infected with the subclone predominating locally. Since ET 12.5/OMP 3L subclone is the most abundant strain isolated in virtually all other Western European countries, these results provide additional evidence that the genetic diversity in the H. influenzae type b population in Europe is relatively restricted.

Epidemiology of nasopharyngeal colonization with nontypeable Haemophilus influenzae in the first 2 years of life

Two hundred children were followed from birth through 2 years of age with nasopharyngeal cultures to determine the normal colonization pattern of nontypeable Haemophilus influenzae. Forty-four percent of the children were colonized on one or more occasions; the acquisition rate was greatest in the first year. Monthly prevalence rates were 11%. Colonization with the initial strain persisted 1-5 months (median, 2). Children carried 1 predominant strain at a time but became colonized with up to 7 different strains (mean, 2.2). Children colonized with a single strain for < or = 2 months produced a greater nasopharyngeal secretory IgA to nontypeable H. influenzae response than did children colonized with different strains (log 2.35 +/- 0.68 vs. 1.89 +/- 0.25 U of P6 secretory IgA/ng/mL of total secretory IgA, P < .01). The duration of colonization with a strain and acquisition of a new strain may be affected in part by the local production of specific secretory IgA.

Bacteremia due to Haemophilus infections: a retrospective study with emphasis on the elderly

We performed a retrospective study of all patients in a large health maintenance organization in Southern California who were identified as having positive blood cultures for Haemophilus organisms during a 20-month period (September 1990 to May 1992) to assess the incidence, presentation, and predisposing conditions of bacteremia due to these organisms and to examine some of the features of these infections in the elderly. Thirty-eight patients with bacteremia due to haemophilus infections were identified. Ten (26.3%) patients were 65 years of age or older. The incidence of bacteremic haemophilus infections in the elderly group was estimated at 2.7 per 100,000 individuals per year, which was almost three times greater than that for the younger age groups studied. When analyzed statistically, the presenting feature of the infection did not differ among age groups. Six patients died, four of whom were elderly. All six deaths were due to nontypable Haemophilus influenzae strains. Cancer was the only chronic underlying condition frequently found among the elderly patients. Three of 10 elderly patients lived in nursing homes; all three were infected with nontypable H. influenzae strains, and all three died.

[Haemophilus influenzae infections in 2 hospitals in the city of Puebla, Mexico]

Haemophilus influenzae has been recognized as one of the most important pathogen in the pediatric population younger than 5 years old. We analized some characteristics of the infectious diseases by Haemophilus influenzae in the pediatric group from 1985 to 1990 in two hospitals of Puebla city. From 321 children studies cases included for this work, fifty of those had infectious diseases by H. influenzae. Forty six percent of the patients developed meningitis, 22% otitis media, 12% sepsis, 10% pneumonia and 10% other infectious diseases. The majority of cases occurred in males but the difference was not statistically significant (p > 0.05). Eighty percent of diseases by H. influenzae occurred in infants younger than 24 months. The serovar b was the most frequent in invasive infections and nontypable strains were frequent in otitis media. The biovars I and IV were isolated from invasive infections. During this study two children died with meningitis and 3 patients had severe neurological damage. This finding suggests that is necessary to vaccine this population to prevent the morbilethality of infectious diseases by Haemophilus influenzae.

Serotypes, biotypes and antibiotic susceptibility of 126 clinical isolates of Haemophilus influenzae

Serotypes, biotypes, and antibiotic susceptibility of 126 Haemophilus influenzae isolates were determined. Five of the 126 isolates were from blood and were encapsulated type b strains; those taken from other sites were not typable. There were 13% biotype I, 36% biotype II, 38% biotype III, 5% biotype IV, 4% biotype V, and 4% biotype VI isolates. Antibiotic susceptibility tests using the standard disk diffusion method showed the following resistance: ampicillin 51%, cefamandole 10%, cefuroxime 3%, chloramphenicol 28%, tetracycline 37% and sulfamethoxazole-trimethoprim 49%. None of the five type b isolates were resistant to cefotaxime, a third generation cephalosporin. The second generation cephalosporins, cefamandole and cefuroxime, showed a superior activity against H. influenzae isolates, compared to other antibiotics. Multiple drug resistance was found in 64 (51%) isolates. Four of the five type b isolates were resistant to multiple drugs. The multiple-resistance pattern most frequently observed was to ampicillin, chloramphenicol, tetracycline and sulfamethoxazole-trimethoprim. Most clinical isolates did not contain plasmids; therefore, the antibiotic resistance of these H. influenzae strains was probably chromosome-mediated.

The isolation and characterization of non-typeable Haemophilus influenzae from the sputum of adult cystic fibrosis patients

The role of non-typeable Haemophilus influenzae in cystic fibrosis (CF) remains unclear. We wanted, therefore, to determine the presence and characteristics of non-typeable H. influenzae in sputum samples from patients with CF. In order to do this, we have assessed sputum samples from 55 consecutive clinically stable patients seen routinely at an adult CF out-patient clinic. Quantitative bacterial culture was performed using a selective media containing cefsoludin, and isolates were characterized by biotyping and outer membrane protein profile analysis. In 17 (30%) of these samples, non-typeable H. influenzae was isolated and was present in similar viable numbers (mean 7.7 x 10(8) colony-forming units (cfu).mL-1; SEM 3.1) to Pseudomonas aeruginosa (mean 8 x 10(8) cfu.mL-1: SEM 2.4). All non-typeable H. influenzae isolates recovered were beta-lactamase negative and sensitive to a range of antibiotics. Several biotypes and outer membrane protein profiles were observed, with no apparent association between these two phenotypic characteristics. The study showed that large numbers of non-typeable H. influenzae are often present in sputum from adult patients with CF. Further longitudinal studies of outer-membrane protein profile analysis are required to determine the dynamics of non-typeable H. influenzae colonization in individual patients and the clinical significance.

Long PCR-ribotyping of nontypeable Haemophilus influenzae

PCR-ribotyping, a new typing method based on long PCR, has been developed for nontypeable Haemophilus influenzae (NTHi). Ribosomal operons of NTHi were amplified by long PCR and were found to be highly polymorphic for internal HaeIII sites. The technique was applied to 49 isolates previously subjected to conventional ribotyping, and the two methods showed a high level of concordance for serial isolates from individual subjects. PCR-ribotyping provides a powerful new typing tool for strain characterization in epidemiological investigations of NTHi.

Expression of capsules by Haemophilus influenzae in mixed infections

The pathogenicity of eight clinical isolates of non-type b Haemophilus influenzae was investigated by inoculating them subcutaneously into mice, alone or mixed with viable or non-viable bacteria of certain other species. Three of the H. influenzae isolates were non-capsulated while five were slightly capsulated (less than 1% of organisms had capsules). The other strains of bacteria tested were four isolates of capsulated and four isolates of non-capsulated pigmented strains of Prevotella sp. and Porphyromonus sp. as well as a capsulate Klebsiella pneumoniae ("helpers"). None of the non-capsulated strains induced an abscess when inoculated alone. Following co-inoculation of viable or non-viable "helpers" with H. influenzae, abscesses were formed in all instances in which the "helper" had a capsule. Profusely capsulated cells of H. influenzae were recovered, however, only from abscesses induced with the five slightly capsulated strains of H. influenzae. These capsulated organisms were found serologically to be of type b and induced abscesses when inoculated alone. Our findings illustrate the ability of non-capsulated strains of H. influenzae to produce progeny of capsulated type b organisms after co-inoculation with certain other species.