Invasive infection with Haemophilus influenzae type b in spite of complete vaccination

Five patients, 4 boys and 1 girl aged 13-41 months, developed invasive Haemophilus influenzae type b (Hib) disease (2 epiglottitis, 3 meningitis) despite full (or at least 3 times) vaccination. At admission as well during convalescence, 3 out of 5 had IgG anti Hib antibody levels < or = 5 U/ml. Serum immunoglobulin levels, including IgG subclasses, as well as complement were normal in all cases. In 2 of the 3, booster vaccinations with Hib conjugate vaccine elicited adequate antibody titres. Since the incorporation of the conjugated Hib polysaccharide tetanus toxoid vaccine (HibTT) in the National Vaccination Programme in the Netherlands, the number of invasive infections caused by Hib has dropped significantly. Causes of Hib conjugate vaccine failures are mostly unknown. In about one-third of the cases serum immunoglobulin levels are deficient, most often IgG2 or IgM. Susceptibility to Hib infection is in part also genetically determined. In the follow-up of Hib vaccine failures, anti Hib antibody titres should be determined. Booster vaccinations may be necessary.     

Effect of dirithromycin on Haemophilus influenzae infection of the respiratory mucosa

Macrolides have properties other than their antibiotic action which may benefit patients with airway infections. We have investigated the effect of dirithromycin (0.125 to 8.0 microg/ml) on the interaction of Haemophilus influenzae with respiratory mucosa in vitro using human nasal epithelium, adenoid tissue, and bovine trachea. Dirithromycin did not affect the ciliary beat frequency of the nasal epithelium or the transport of mucus on bovine trachea, but dirithromycin (1 microg/ml) did reduce the slowing of the ciliary beat frequency and the damage to the nasal epithelium caused by H. influenzae broth culture filtrate. Amoxicillin (2 microg/ml) did not reduce the effects of the H. influenzae broth culture filtrate. H. influenzae infection of the organ cultures for 24 h caused mucosal damage and the loss of ciliated cells. Bacteria adhered to damaged epithelium and to a lesser extent to mucus and unciliated cells. Incubation of H. influenzae with dirithromycin at sub-MICs (0.125 and 0.5 microg/ml) prior to infection of the organ cultures did not reduce the mucosal damage caused by bacterial infection. By contrast, incubation of adenoid tissue with dirithromycin (0.125 to 1.0 microg/ml) for 4 h prior to assembling the organ culture reduced the mucosal damage caused by subsequent H. influenzae infection by as much as 50%. The number of bacteria adherent to the mucosa was reduced, although the tissue that had been incubated with dirithromycin (0.125 and 0.5 microg/ml) did not inhibit bacterial growth. This was achieved by a reduction in the amount of damaged epithelium to which H. influenzae adhered and a reduction in the density of bacteria adhering to mucus. We conclude that dirithromycin at concentrations achievable in vivo markedly reduces the mucosal damage caused by H. influenzae infection due to a cytoprotective effect.     

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.     

An economic analysis of alternatives for childhood immunisation against Haemophilus influenzae type b disease

Cost-effectiveness and cost-utility analyses of immunisation strategies against invasive Haemophilus influenzae type b (Hib) disease in Australia were based on a hypothetical birth cohort of 250,000 non-Aboriginal Australian children. The model predicted that, without immunisation, 625 cases of invasive Hib disease would occur in under-five-year-olds, with direct costs of $10.2 million. Universal public sector vaccination beginning before six months of age (6MVAC) prevented 80 per cent of cases; vaccination at 12 months (12MVAC) 62 per cent and at 18 months (18MVAC) 46 per cent. At a vaccine cost of $15 per dose, 18MVAC gave the lowest cost per quality-adjusted life year (QALY) over a wide range of model assumptions, with 6MVAC the 'best' alternative. The best estimate ($ per QALY) for 6MVAC was $6930 (three doses), for 12MVAC $9136 (two doses) and for 18MVAC $1231 (one dose). The cost per QALY of single dose catch-up immunisation of older children was estimated at $8630 at two years, $27,000 at three years and $117,000 at four years if done at a scheduled visit; these values were increased if an additional medical visit was included. The threshold cost per vaccine dose at which an immunisation program became cost-saving was estimated for 6MVAC, 12MVAC and 18MVAC as $11, $10 and $14. Even under a worst-case scenario, an immunisation program at 6, 12 or 18 months became cost-saving if indirect costs of death were included. Comparison with previous analyses revealed the importance of the incidence and age distribution of disability and assumptions about vaccine administration costs in determining model outcomes.     

Nasopharyngeal colonization with nontypeable Haemophilus influenzae in chinchillas

Colonization of the nasopharynx by a middle ear pathogen is the first step in the development of otitis media in humans. The establishment of an animal model of nasopharyngeal colonization would therefore be of great utility in assessing the potential protective ability of candidate vaccine antigens (especially adhesins) against otitis media. A chinchilla nasopharyngeal colonization model for nontypeable Haemophilus influenzae (NTHI) was developed with antibiotic-resistant strains. This model does not require coinfection with a virus. There was no significant difference in the efficiency of NTHI colonization between adult (1- to 2-year-old) and young (2- to 3-month-old) animals. However, the incidence of middle ear infection following nasopharyngeal colonization was significantly higher in young animals (83 to 89%) than in adult chinchillas (10 to 30%). Chinchillas that had recovered either from a previous middle ear infection caused by NTHI or from an infection by intranasal inoculation with NTHI were completely protected against nasopharyngeal colonization with a homologous strain and were found to be the best positive controls in protection studies. Systemic immunization of chinchillas with inactivated whole-cell preparations significantly protected animals not only against homologous NTHI colonization but also partially against heterologous NTHI infection. In all protected animals, significant serum anti-P6 and anti-HMW antibody responses were observed. The outer membrane P6 and high-molecular-weight (HMW) proteins appear to be promising candidate vaccine antigens to prevent nasopharyngeal colonization and middle ear infection caused by NTHI.     

Bacteremia caused by Haemophilus influenzae with special reference to its relation to HIV infection

The present study was undertaken to reveal the magnesium distribution in human bone. Sixty human ribs, obtained from subjects aged 10-80 years of age, were used. Transverse sections were prepared from the middle region of the human ribs. Adjacent sections were ground to a thickness of about 1000 microns. One section was used for magnesium determination by atomic absorption spectrophotometry, and the other was used for analysis with X-ray microanalysis. Thirty micron thick samples were abraded continuously from the periosteal and the endosteal surfaces by abrasive microsampling, as previously described by Weatherell et al. Results showed that magnesium concentrations were higher in both the periosteal and endosteal surfaces and did not change with age in general, although it tended to be higher among teenagers and lower over 80 years old.     

Human lactoferrin receptor activity in non-encapsulated Haemophilus influenzae

We recently reported that attenuation of vasoactive agent-induced calcium signal and cell contraction of mesangial cell by insulin-like growth factor 1 (IGF-1), observed in normal mesangial cells, is totally abolished in spontaneously hypertensive rat (SHR) mesangial cells. This phenomenon might be related to the well-known aberrant regulation of SHR glomerular hemodynamics. Since it has been reported that in vivo IGF-1 infusion increases renal plasma flow (RPF) and glomerular filtration rate (GFR), we examined whether the modulation of renal function by IGF-1 is altered in SHR. We performed in vivo renal clearance studies using eight-week-old SHR and control Wistar Kyoto rats (WKY) before and after IGF-1 (5 micrograms/kg) infusion into the left renal artery for 20 minutes. Mean arterial pressure was not affected by IGF-1 in both WKY and SHR. In WKY, IGF-1 increased GFR and RPF, and decreased renal vascular resistance (RVR). However, GFR, RPF, and RVR were not altered by IGF-1 in SHR, while systemic infusion of angiotensin II antagonist, CV-11974, increased GFR and RPF. The present data show that the modulation of renal hemodynamics by IGF-1 is absent in SHR. This might be related the pathophysiology of the development of hypertension.     

Nontypeable Haemophilus influenzae: pathogenesis and prevention

In this paper, we describe the ability of nontypeable Haemophilus influenzae (NTHi) to coexist with the human host and the devastating results associated with disruption of the delicate state of balanced pathogenesis, resulting in both acute and chronic respiratory tract infections. It has been seen that the strains of NTHi causing disease show a marked genetic and phenotypic diversity but that changes in the lipooligosaccharide (LOS) and protein size and antigenicity in chronically infected individuals indicate that individual strains of NTHi can remain and adapt themselves to avoid expulsion from their infective niche. The lack of reliance of NTHi on a single mechanism of attachment and its ability to interact with the host with rapid responses to its environment confirmed the success of this organism as both a colonizer and a pathogen. In vitro experiments on cell and organ cultures, combined with otitis media and pulmonary models in chinchillas, rats, and mice, have allowed investigations into individual interactions between NTHi and the mammalian host. The host-organism interaction appears to be a two-way process, with NTHi using cell surface structures to directly interact with the mammalian host and using secreted proteins and LOS to change the mammalian host in order to pave the way for colonization and invasion. Many experiments have also noted that immune system evasion through antigenic variation, secretion of enzymes and epithelial cell invasion allowed NTHi to survive for longer periods despite a specific immune response being mounted to infection. Several outer membrane proteins and LOS derivatives are discussed in relation to their efficacy in preventing pulmonary infections and otitis media in animals. General host responses with respect to age, genetic makeup, and vaccine delivery routes are considered, and a mucosal vaccine strategy is suggested.     

Mathematical models of Haemophilus influenzae type b

Electron microscopic anterograde autoradiography has been used to analyze the morphology and postsynaptic relationships of area 17 cortical terminals in the lateral division of the lateral posterior nucleus (LPl) of the cat and medial division of the inferior pulvinar nucleus (IPm) of the owl monkey. Such terminals are thought to arise exclusively from layer 5 in the cat and primate (Lund et al. [1975] J. Comp. Neurol. 164:287-304; Abramson and Chalupa [1985] Neuroscience 15:81-95). All labeled terminals in both nuclei exhibited the morphology of ascending "lemniscal" afferents. That is, they contained round vesicles, were large, made asymmetrical synaptic and filamentous nonsynaptic contacts, and were classified as RLs. These cortical RLs also exhibited the postsynaptic relationships of lemniscal afferents. Thus, they were presynaptic to large dendrites within glial encapsulated glomeruli, where a majority was involved in complex synaptic arrangements called triads. They also were found adjacent to terminal profiles with pleomorphic vesicles but never adjacent to small terminals containing round vesicles. Our results suggest that the layer 5 projection from area 17 provides a functional "drive" for some LPl and IPm neurons. Information carried over this "re-entrant" pathway (Guillery [1995] J. Anat. 187:583-592) could be modified within the LPl and IPm by both cortical and subcortical pathways and subsequently conveyed to higher visual cortical areas, where it could be integrated with messages carried through the well-documented corticocortical pathways (Casagrande and Kaas [1994] Cerebral cortex New York: Plenum Press).     

Early onset Haemophilus influenzae sepsis in the newborn infant

Neonatal sepsis caused by Haemophilus influenzae is characterized by an early onset syndrome associated with pneumonia, shock and neutropenia. Over a 30-month period 13 infants referred to this hospital had early onset H. influenzae sepsis. Obstetric complications included preterm labor (92%), prolonged rupture of membranes > 12 hours (63%), maternal fever (64%), chorioamnionitis (43%), vaginal discharge (44%) and premature rupture of membranes (15%). All 13 infants were symptomatic at delivery and 7 required immediate intubation. Pneumonia and respiratory distress were the prominent clinical findings. H. influenzae was isolated from infant blood, maternal blood, placenta and genital tract. Isolates were predominantly non-type b, beta-lactamase-negative. A study to determine the prevalence of H. influenzae colonization of the genital tract among women attending clinic at the hospital with the most cases showed a rate of 0.3%. Perinatal risk factors and clinical findings in the infants are similar to disease caused by other organisms associated with early onset sepsis.     

Protective effect of breastfeeding on invasive Haemophilus influenzae infection: a case-control study in Swedish preschool children

BACKGROUND: In Orebro County a 2.5-fold increase in the incidence of Haemophilus influenzae (HI) meningitis was found between 1970 and 1980, an observation that initiated the present study. MATERIALS AND METHODS: In order to search for associations between morbidity in invasive HI infection and possible risk factors, a case-control study was conducted over a 6-year period from 1987 to 1992, before general Hib vaccination was introduced in Sweden. Fifty-four cases with invasive HI infection 139 matched controls were studied for possible risk factors such as day-care outside the home, short duration of breastfeeding, passive smoking, low socioeconomic level of the household, many siblings in the family, allergy, frequent, infections, repeated antibiotic treatments and immunoglobulin deficiency. RESULTS: Multivariate analysis showed a significant association between invasive HI infection and two independent factors, i.e. short duration (< 13 weeks) of exclusive breastfeeding, odds ratio (OR) 3.79 (95% confidence interval [CI] 1.6-8.8) and history of frequent infections, OR 4.49 (95% CI : 1.0-21.0). For the age at onset 12 months or older, the associations were stronger, OR 7.79 (95% CI : 2.4-26.6) and 5.86 (95% CI : 1.1-30.6), respectively. When breastfeeding duration in weeks was analysed as a continuous variable the OR was 0.95 (95% CI : 0.92-0.99), indicating a decreased risk with each additional week. Increased OR were observed for other risk factors as well but not of the magnitude found for short duration of breastfeeding. DISCUSSION: The association of decreased risk for invasive HI infection and long duration of breastfeeding was persisting beyond the period of breastfeeding itself. This finding supports the hypothesis of a long-lasting protective effect of breastfeeding on the risk for invasive HI infection. CONCLUSION: A decreased risk for invasive HI infection with long duration of breastfeeding was found. Our results do have implications for strategies in breastfeeding promotion, especially in countries where Hib vaccination is too costly and not yet implemented.     

Clonality of multidrug-resistant nontypeable strains of Haemophilus influenzae

The genetic structure of a population of multidrug-resistant nontypeable (unencapsulated) Haemophilus influenzae strains isolated at a hospital in Barcelona, Spain, was investigated by using multilocus enzyme electrophoresis to determine the allelic variation in 15 structural loci. In our study we have also included some antimicrobial agent-susceptible strains isolated at the same hospital. All enzymes were polymorphic for two to eight electromorphs, and the analysis revealed 43 distinct electrophoretic types among the 44 isolates. The mean genetic diversity of the entire population was 0.55. Multilocus linkage disequilibrium analysis of the isolates revealed a strong association between alleles, suggesting little possibility of recombination. Furthermore, the dendrogram and the allele mismatch distribution are typical of a population with no extensive genetic mixing.     

The decline of Haemophilus influenzae type b disease in Australia

Between July 1993 and June 1996, there were 412 cases of invasive Haemophilus influenzae type b (Hib) disease reported to the Hib Case Surveillance Scheme, 71% in children under the age of five years. Meningitis was the most frequent illness reported, followed by epiglottitis, septicaemia and pneumonia. There were 18 deaths. Thirty-four cases were classified as vaccine failures. The number of vaccine failures increased over time and the total number of cases of Hib disease fell, consistent with an increase in Hib vaccine coverage. Based on an estimated vaccine coverage of 50% in April 1995, the vaccine efficacy for all vaccines in the period was estimated to be 89%. Invasive Hib is a serious illness of childhood which is being significantly reduced by the use of Hib vaccines, and has the potential to be eliminated from this country. Vaccination providers should aim to immunise all children against Hib disease on time and according to the National Health and Medical Research Council Standard Vaccination Schedule.     

Haemophilus influenzae type b-specific antibody in infants after maternal immunization

OBJECTIVE: To study the kinetics of Haemophilus influenzae type b (Hib)-specific antibody in infants born to mothers immunized with an Hib polysaccharide or one of two Hib conjugate vaccines. STUDY DESIGN: Serum antibody to the polyribosylribitol (PRP) moiety of Hib was measured by radioimmunoassay and enzyme-linked immunosorbent assay at birth and at 2 and 6 months of age in infants born to women immunized with Hib polysaccharide or conjugate vaccine (PRP-D and HbOC). A subset of infants > or = 6 months of age was immunized with Hib conjugate vaccine after licensure of this vaccine for infants. A comparison group of 18 infants born to unimmunized women received the same Hib conjugate vaccine on a similar schedule. RESULTS: Total PRP antibody concentrations were 1.50, 14.4 and 20.4 microg/ml in 2-month-old infants born to mothers immunized with polysaccharide, PRP-D and HbOC vaccines, respectively, and 2.54, 1.35 and 2.46 microg/ml in 6-month-old infants. Infants born to mothers immunized with polysaccharide vaccine had significantly less PRP antibody at 2 months of age but similar antibody concentrations at 6 months of age. Persistence or increases in total PRP antibody during 6 months were noted in 21 of 47 (44.6%) study infants. A subset of study and comparison infants was immunized with a mean of 2.6 doses of Hib vaccines between 6 months and 2 years of age, and all infants had total PRP antibody concentrations > or = 0.15 microg/ml. CONCLUSION: Conjugate Hib vaccines administered during the last trimester of pregnancy resulted in significantly higher PRP antibody titers in infants at birth and 2 months of age than did polysaccharide vaccine. A subset of infants born to immunized mothers was subsequently immunized with Hib conjugate vaccine and had antibody concentrations similar to those in infants born to nonimmunized women.     

The biologic activities of peptidoglycan in experimental Haemophilus influenzae meningitis

While gram-positive bacterial cell walls are known to incite inflammation, the contribution of gram-negative peptidoglycan to disease has not been characterized. The ability of cell wall, purified peptidoglycan, and soluble peptidoglycan subcomponents from Haemophilus influenzae to provoke inflammation was determined in a rabbit model of meningitis. Haemophilus peptidoglycan, with or without associated proteins, produced brain edema at > or = 0.1 micrograms/mL of cerebrospinal fluid (CSF); leukocytosis and protein accumulation in CSF occurred only at > or = 10.0 micrograms/mL of CSF. Solubilized peptidoglycan was 10-fold more active than intact cell wall. The bioactivity of peptidoglycan from ampicillin-resistant H. influenzae was at least twofold greater than that of ampicillin-sensitive strains. Consistent with these pathologic effects of purified peptidoglycan, ampicillin-induced bacterial lysates in which endotoxin was neutralized induced brain edema and protein influx but little leukocytosis. Thus, peptidoglycan seems to contribute to the pathology of gram-negative meningitis, particularly brain edema.     

Polymerase chain reaction-based strain characterization of noncapsulate Haemophilus influenzae

A polymerase chain reaction-based typing method for noncapsulate Haemophilus influenzae was developed. Randomly amplified polymorphic DNA fingerprints were generated from boiled supernatants prepared directly from bacterial colonies without the need for DNA extraction. The technique was applied to isolates obtained during putative outbreaks of chest infection and validated by comparison with sodium dodecyl sulfatepolyacrylamide gel electrophoresis analysis of outer membrane protein-enriched preparations and rRNA gene restriction analysis. There was complete concordance between the three techniques. The results show that randomly amplified polymorphic DNA analysis provides a highly discriminatory method of characterizing strains of noncapsulate H. influenzae which is eminently suitable as an epidemiological tool for the rapid investigation of outbreaks of infection.