Non-type b Haemophilus influenzae meningitis

Long Term Impact of Conjugate Vaccines on Haemophilus influenzae Meningitis: Narrative Review

H. influenzae serotype b (Hib) used to be the commonest cause of bacterial meningitis in young children. The widespread use of Hib conjugate vaccine has profoundly altered the epidemiology of H. influenzae meningitis. This short review reports on the spectrum of H. influenzae meningitis thirty years after Hib conjugate vaccine was first introduced into a National Immunization Program (NIP). Hib meningitis is now uncommon, but meningitis caused by other capsulated serotypes of H. influenzae and non-typeable strains (NTHi) should be considered. H. influenzae serotype a (Hia) has emerged as a significant cause of meningitis in Indigenous children in North America, which may necessitate a Hia conjugate vaccine. Cases of Hie, Hif, and NTHi meningitis are predominantly seen in young children and less common in older age groups. This short review reports on the spectrum of H. influenzae meningitis thirty years after Hib conjugate vaccine was first introduced into a NIP.

Reflections on pneumonia in the tropics

This review of pneumonia in the tropics is based on experience with respiratory infectons in Papua New Guinea since the 1970s. It discusses ideas, principles, historical aspects of pneumonia research and the need to work with people in the community. In order to understand pneumonia in a tropical setng and evaluate new interventons it is essental to study the ecosystem of the causatve infectons, within the host and the community and between interactng microorganisms. Vaccines are much-needed preventve tools, and for pneumonia in a highly endemic setng the preventon of severe and fatal disease takes priority over the preventon of infecton. In this setng mild infecton plays an important role in preventng severe disease. For achieving long-term sustainable outcomes, sometmes ‘less is more’. A multpronged approach is required to control and prevent pneumonia, and in devising new ways of doing so. This includes appropriate and accessible clinical care, a clean, smoke-free environment, good nutriton and a range of vaccines. Also required are persistent advocacy from the global scientfc community and strong engagement with and by the communites that bear the burden of disease. Beter health care must be pursued in conjuncton with raising literacy rates and reducing poverty.

Kinetic Th1/Th2 responses of transgenic mice with bacterial meningitis induced by Haemophilus influenzae

To investigate the kinetic Th1/Th2 immunopathogenic mechanisms of Haemophilus influenzae meningitis, we established a murine experimental model of meningitis and elucidated the Th1/Th2 immune responses in T1/T2 doubly transgenic mice based on a BALB/c background under the control of the IFN-gamma (interferon-gamma)/IL-4 (interleukin-4) promoters respectively. NTHi (non-typeable Haemophilus influenzae) meningitis was induced in these mice by inoculation with either a colonized (CNTHi) or invasive (INTHi) strain of NTHi. Mice inoculated with CNTHi displayed a less severe degree of disease in terms of clinical symptoms, mortality rate and brain histopathology. Conversely, INTHi-inoculated mice had more severe clinical symptoms. CNTHi-inoculated mice had a more significant Th1 response in terms of a higher percentage and longer maintenance of Th1 cells, and more production of IFN-gamma from strain-specific antigen-stimulated splenocytes than INTHi-inoculated mice. In contrast, INTHi-inoculated mice had a more significant Th2 response. This was due to a significant increase in IL-4-producing CD4(+) T-cells (Th2 cells) and more production of IL-4 from strain-specific antigen-stimulated splenocytes accompanied by a rapid decline of Th1 cells in INTHi-inoculated mice. In conclusion, the preferential Th1/Th2 trend in this murine model of NTHi meningitis is correlated with clinical severity as well as isolated characteristics of the pathogens themselves.

Analysis of invasive Haemophilus influenzae infections after extensive vaccination against H. influenzae type b

Little clinical and microbiological information is available about invasive Haemophilus influenzae infection after widespread vaccination against H. influenzae type b (Hib). We conducted an active community surveillance study on invasive H. influenzae during a 2-year period in a community of more than 5 million people after vaccination against Hib in children was introduced. The median incidence was 16.3 cases/100000 persons per year in children less than 1-year-old and 4.41 cases/100000 persons in children less than <5 years old. The highest incidence in adults was observed in patients greater than 70 years old. Clinical diagnoses included bacteremia, pneumonia, and meningitis. Of the H. influenzae-infected patients, 74.3% had underlying predisposing conditions, including impaired immunity and respiratory diseases. A total of 73.6% of the isolates were nontypeable and 16.5, 6.6, and 3.3% were types b, f, and e, respectively. Infections due to capsulated strains b, e, and f were evenly distributed between children and adults. Ampicillin and cotrimoxazole resistance occurred at frequencies of 24.2 and 48.4%, respectively. Antibiotic resistance was more prevalent in capsulated than in noncapsulated H. influenzae. Invasive isolates were highly resistant to antibiotics that were used infrequently in the community. Nontypeable H. influenzae were genetically much more heterogeneous than capsulated strains. Capsule-deficient mutants (b(-)) were not detected. Plasmid carriage was linked to antibiotic resistance and capsulated strains. Over the study period, the incidence of invasive H. influenzae infections, either encapsulated or not, did not increase. In the post-Hib vaccination era, most invasive infections were due to noncapsulated strains and occurred in the extreme ages of life in patients with predisposing conditions.

Intramuscular ceftriaxone in the treatment of childhood meningitis due to Haemophilus influenzae type F

OBJECTIVE

To describe a case of meningitis caused by Haemophilus influenzae type f (Hif) in a child.

CASE SUMMARY

A 2.5-year-old white girl (18 kg) was hospitalized because of acute ataxia. The cerebrospinal fluid culture grew H. influenzae, which was later identified as type f. Therapy was limited by the inability to gain intravenous access. Treatment was initiated with dexamethasone 8 mg (0.44 mg/kg) intramuscularly, one dose on the day prior to initiation of ceftriaxone therapy, and intramuscular ceftriaxone 2 g (111 mg/kg/dose) once a day. After the first day, dexamethasone was administered at 3 mg (0.17 mg/kg/d) orally four times per day for four days. Within two days, the patient became afebrile and improved significantly. The remaining treatments were given during daily hospital visits on an outpatient basis. No complications occurred during the follow-up visits.

DISCUSSION

The clinical presentation and therapeutic management of Hif meningitis is similar to that of H. influenzae type b (Hib) meningitis. Factors that may predispose a child to infections caused by Hif include upper respiratory tract infections, day care attendance, Down syndrome, and immunodeficiency. Hif meningitis usually is treated with a third-generation cephalosporin (frequently ceftriaxone). Although most often administered intravenously, intramuscular ceftriaxone can provide a satisfactory clinical outcome in a child with adequate peripheral perfusion but limited intravenous access. The majority of reported cases of Hif meningitis resolve with appropriate antibiotic therapy; however, long-term neurologic sequelae occasionally occur.

CONCLUSIONS

Hif occasionally causes pediatric meningitis. In a patient with good perfusion and difficult intravenous access, daily intramuscular administration of ceftriaxone can be an effective treatment option. In this case, Hif meningitis occurred abruptly and resolved within 48 hours of initiation of ceftriaxone and dexamethasone without long-term sequelae. The risks of giving dexamethasone appear to be minimal, although efficacy for preventing Hif complications remains to be proven.

Haemophilus influenzae: then and now

Haemophilus influenzae has long been recognised as a major cause of serious infection and mortality in children less than 5 years old. Prior to the introduction of Haemophilus influenzae type b (Hib) immunisation, the incidence of a child suffering an invasive Haemophilus infection was 20-50/100,000 in industrialised countries and up to ten times higher in developing regions. The introduction of a Hib vaccine programme results in a rapid and dramatic decline in the incidence of Hib infection in the susceptible childhood population. For example, within two years of the introduction of routine Hib vaccination of infants in the UK, the risk of serious Hib infection had fallen from 1:600 to 1:30,000 by 5 years of age. Many other European countries have introduced, or are in the process of introducing, a routine Hib immunisation programme. Because the epidemiology of Haemophilus influenzae infection is changing so dramatically, it is opportune to review Haemophilus influenzae as it was perceived in the pre-vaccine era (the past) and during vaccine implementation (the present), and how its role may change in the post-vaccination era (the future). This review will summarise the historical landmarks that have led to our present-day understanding of Haemophilus influenzae pathogenicity, the concerns about antibiotic resistance, the features of the host immune response to Haemophilus influenzae, and the introduction of the Hib vaccine. Furthermore, the possible importance of this organism in the future will be discussed.

Biotypes and serotypes of Haemophilus influenzae from patients with meningitis in the city of São Paulo, Brazil

A total of 1,094 Haemophilus influenzae isolates from cerebrospinal fluid were examined by biochemical and serological means. Most of them belonged to biotype I (70.9%) and to serotype b (99.4%). The relationship of biotypes I and II to the ages of the patients was shown to be significant (P < 0.001).

Molecular epidemiology of Haemophilus influenzae type b in the Gambia

One hundred two invasive and 64 noninvasive isolates of Haemophilus influenzae were collected in the course of a 2-year prospective field study on the epidemiology of H. influenzae meningitis in The Gambia. The isolates were serotyped, biotyped, and subtyped by outer membrane protein (OMP) profile analysis (OMP subtyping). H. influenzae meningitis was found to be caused by serotype b (95%). In invasive disease, serotype a, although present in the throat of healthy children, caused only occasionally (5.9%) disease. The distribution of biotypes of H. influenzae appeared to be very similar to that found outside The Gambia. A distinct pattern of OMP subtypes, different from other parts of the world, is prevalent in H. influenzae type b (Hib) in The Gambia. OMP subtypes 2, 4, 5, 8, and 9 were observed to be predominant. These subtypes, except subtype 2, have not been described. L subtypes (subtypes 2, 4, and 8) were associated with invasive disease, whereas non-L subtypes (subtypes 5 and 9) were found more often in healthy carriers (P less than 0.001). A significant difference in geographical distribution was found in subtypes of noninvasive Hib strains (P less than 0.05). We conclude that in The Gambia H. influenzae invasive disease is caused mainly by type b strains with a limited number of OMP subtypes, which are different from the subtypes found elsewhere in the world. These data are important for the surveillance of Hib disease in developing countries and are baseline data for a Hib polyribosyl-ribitolphosphate-conjugated vaccine trial in The Gambia. Alternative Hib OMP vaccines should include a set of representative OMPs.

World-wide epidemiology of Haemophilus influenzae meningitis; industrialized versus non-industrialized countries

The epidemiology of Haemophilus influenzae meningitis in non-industrialized areas shows considerable differences from that in the industrialized world. The incidence rates among Alaskan Eskimos, Navaho and White Mountain Indians, Australian Aboriginals and among populations in Africa such as Gambians and Senegalese are three- to fourfold higher than those in the USA and up to ten times higher than those in Europe. The peak age in populations with a high incidence is around 5 to 6 months of age compared to 9 months of age in other countries. The case fatality rate (CFR) is not related to the state of industrialization but seems to be more dependent on the accessibility of health care facilities. Africa the CFR is about ten times higher than that seen elsewhere. Apart from other dissimilarities such as the pattern of serotypes causing disease and the transmission rate, the epidemiology of Hib disease is sufficiently different from industrialized areas that it demands a thorough testing of a conjugated Hib vaccine before it can be introduced on a large scale in populations in non-industralized areas.

Carriage of Haemophilus influenzae in healthy Gambian children

1240 throat samples were processed during different seasons in 11 different communities of The Gambia (West Africa). The carriage rate for Haemophilus influenzae type b ranged from 0 to 33%, but often attained 10% or more, higher than that reported from other open communities. The duration of carriage was short (less than 3 months) and H. influenzae b was found in only 10% of the carriers isolated during the previous or the following survey. Children less than 5 years old carried H. influenzae b in their throat significantly more often than children older than 14 years (P less than 0.05). A high carriage rate did not correlate with the wet or dry season. The carriage rate of children in rural areas was similar to that of children in urban areas. Children in day-care centres or nurseries had a surprisingly low carriage rate (2%). The carriage rate of H. influenzae b was compared to the presence of H. influenzae subspecies in a random sample, which revealed that H. influenzae subspecies was found in 90% of the children under 5 years old. Encapsulated strains of H. influenzae were found in 25% of the same sample, two-thirds of which were not type b. All capsule types were represented. No meningitis cases occurred in the survey populations. We conclude that the prevalence of H. influenzae b in open Gambian communities is similar to that in closed communities elsewhere, but that the kinetics are different from those in closed communities, as persistence of infection in Gambian children is short-lived.

Childhood acute bacterial meningitis in the Sudan: an epidemiological, clinical and laboratory study

The aims of the present study were to document the epidemiology, clinical features and complications of childhood acute bacterial meningitis (ABM) in The Sudan during both an inter-epidemic (endemic) period (1985-1986), and the 1988 serogroup A epidemic; and to examine the phenotypic and genetic similarities and differences of Neisseria meningitidis strains isolated in The Sudan and Sweden. A new enzyme immunoassay test (Pharmacia Meningitis EIA-Test) was evaluated as a potential rapid diagnostic method for the detection of Haemophilus influenzae (HI) type b, Neisseria meningitidis (MC) and Streptococcus pneumoniae (PNC). The test was found to have good sensitivity (0.86) and specificity (0.95) in the inter-epidemic period; and to be adaptable to the field work in The Sudan during the 1988 MC epidemic. During inter-epidemic (endemic) situations in The Sudan, greater than 90% of childhood ABM was caused by one of the three organisms, HI type b, MC and PNC. HI accounted for 57% of the cases. The peak incidence (76%) of HI cases was in infants (less than 12 months) similar to the situation in other African countries. The overall case fatality ratio was 18.6%. Prospective follow-up of survivors for 3-4 years revealed that an additional 43% either died or had permanent neurological complications, the most prevalent and persistent of which was sensorineural hearing loss recorded in 22% of long term survivors. Post-meningitic children were found to have significantly lower intelligence quotients (92.3 +/- 13.9) than their sibling controls (100.7 +/- 10.2, P = 0.029). Features of the large serogroup A sulphonamide resistant MC epidemic (February-August 1988) in Khartoum are described. An estimated annual incidence of 1,679/100,000 was recorded at the peak of the epidemic. The highest attack rate was in young children less than 5 years, as in many other African countries; nevertheless, a high morbidity was observed in adults (31% of the cases greater than or equal to 20 years). The clinical features, mortality (6.3%) and short term sequelae in Sudanese children were generally within the framework described for MC disease elsewhere. Detailed analysis of MC isolates from Sudan and Sweden by characterizing their electrophoretic enzyme types, DNA restriction endonuclease pattern and outer membrane proteins, revealed that serogroup A MC clone III-1 was responsible of The Sudan epidemic in 1988 and has been the dominant serogroup A organism in Sweden since 1973. The Sudanese strains isolated prior to the epidemic (1985) were clone IV-1.(ABSTRACT TRUNCATED AT 250 WORDS)

Evolutionary genetics of the encapsulated strains of Haemophilus influenzae

Genetic relationships among 2209 isolates of Haemophilus influenzae of polysaccharide capsule serotypes a, b, c, d, e, and f were determined by analyzing electrophoretically demonstrable allelic variation at 17 chromosomal enzyme loci. We distinguished 280 electrophoretic types (ETs), representing distinctive multilocus genotypes. Genetic diversity among ETs of isolates of the same serotype was, on average, only 67% of that in the total sample, and no ETs were shared among isolates of different serotypes. Cluster analysis of the ETs revealed 2 primary phylogenetic divisions at a genetic distance of 0.66 and 12 major lineages diverging from one another at distances greater than 0.42. In general, strains of different phylogenetic lines or groups of allied lineages have characteristic cap region restriction fragment length polymorphism patterns obtained by digestion of genomic DNA with EcoRI. Strains producing serotype c, e, and f capsules have no close relationships to those of other encapsulated strains. Lineages of both serotype a and b strains occur in each primary phylogenetic division, most probably as a result of the transfer of serotype-specific sequences of the cap region between clonal lineages. Serotype a strains allied in division I with a group of abundant serotype b clones and the serotype d strains apparently are more virulent than the serotype a strains in division II, which are related to serotype b and f strains that rarely cause invasive disease.

Clonal population structure of encapsulated Haemophilus influenzae

Chromosomal genotypes of 2,209 isolates of the six polysaccharide capsule types of Haemophilus influenzae recovered from human hosts worldwide were characterized by an analysis of electrophoretically demonstrable allelic profiles at 17 metabolic enzyme loci. For 222 representative isolates, restriction fragment length polymorphism patterns produced by digestion of cap region DNA were also determined. With few exceptions, isolates belonging to individual phylogenetic lines or groups of allied lineages identified by multilocus enzyme electrophoresis had characteristic cap region restriction fragment length polymorphism patterns and characteristic combinations of cap region patterns and outer membrane protein types. The occurrence of strong associations of characters and the recovery of isolates with identical genetic properties in widely separated geographic regions and over a 40-year period indicated that the population structure of encapsulated H. influenzae is clonal. Recombination of chromosomal genes, including those mediating capsule synthesis, apparently is not a major factor in the short-term evolution of these pathogenic organisms and, therefore, may be of minor clinical significance.