Specific latex preparations in the etiological diagnosis of suppurative bacterial meningitis

The results of the evaluation of the diagnostic latex preparations Bactigen, manufactured by Wampole Laboratories (USA) and intended for the detection of meningococcal antigens, serogropus A, B, C, Y, pneumococcal polyantigens and type b Haemophilus influenzae antigens in the spinal fluid and blood of patients with meningococcal infection and purulent bacterial meningitides, are presented. The pathological material was studied by traditional methods and by the latex agglutination (LAG) test. 522 LAG tests were made, including 414 tests for meningococcal infection, 60 tests for pneumococcal infection and 48 tests for type b H. influenzae. The results of this study revealed that the latex preparations were highly specific with respect to type b H. influenzae antigens and meningococcal antigens (false positive reactions constituted 0.96%). The simplicity of the test and the rapid techniques making it possible to obtain results within 30-40 minutes indicate good prospects of using the LAG test in laboratory practice.     

b型流感嗜血杆菌培养及细菌溶解产物制备工艺研究

目的研究b型流感嗜血杆菌(Haemophilus influenza type b,Hib)培养条件及细菌溶解产物制备工艺。方法比较Hib在传统培养基和改良培养基的生长情况,优化改良培养基在生物反应器中对Hib培养条件(p H值、温度、溶解氧等),研究最佳菌体细胞破碎方法及细菌溶解产物纯化制备工艺。结果改良培养基可代替传统培养基用于Hib的生产培养,且Hib在p H7.4、温度为36℃、溶解氧为25%的改良培养基中,生长迅速,菌体产量最高。高压匀浆破碎法的破碎效果明显优于超声波破碎法,破碎效果达到98%以上,纯化后的细菌溶解产物的多糖含量、总氮含量、蛋白质含量、核酸含量及细菌内毒素含量均符合《中华人民共和国药典》(三部)2010版中b型流感嗜血杆菌结合疫苗的质量标准。结论初步建立了b型流感嗜血杆菌培养及细菌溶解产物制备工艺。     

Human serum bactericidal activity against Haemophilus influenzae type b

We examined bactericidal and opsonizing activity of pooled adult 'immune' serum against Haemophilus influenzae type b with and without the addition of phagocytes. Four type b strains from cerebrospinal fluid (CSF) and three such strains from the nasopharynx (NP) of healthy children were examined. Duplicate reaction mixtures contained organisms in exponential (E) or stationary phase (S) of growth, serum, a complement source (human agammaglobulinaemic serum), and culture medium (bactericidal assay); separate assays contained the above components and polymorphonuclear leucocytes (opsonization system). A decrease in bacterial density of greater than or equal to 1 log10 unit was considered significant. All four S-CSF strains, three of four E-CSF strains and one of three S-NP strains were sensitive to the bactericidal activity of pooled serum. The other E-CSF strain, two S-NP strains and all three E-NP strains were resistant to the bactericidal activity of pooled serum. Two of three E-NP strains were opsonized by pooled serum; the other strains resistant to the bactericidal activity of pooled serum were also resistant to opsonization. Bactericidal and opsonizing activity of serum from an immunized adult was greater than or equal to that of pooled serum against each strain. Assuming normal adults are immune to invasive H. influenzae type b infection, an experimental test reflecting this immunity is the bactericidal activity against CSF isolates tested in stationary phase. We conclude that protection against invasive disease due to H. influenzae type b appears more complex than the presence of bactericidal and opsonizing activity in serum.     

Association between type 1 diabetes and Haemophilus influenzae type b vaccination: birth cohort study

ObjectivesTo determine the effect of Haemophilus influenzae type b vaccination and its timing on the risk of type 1 diabetes in Finnish children.DesignCumulative incidence and relative risk of type 1 diabetes was compared among three birth cohorts of Finnish children: those born during the 24 months before the H influenzae type b vaccination trial, those in the trial cohort who were vaccinated at 3 months of age and later with a booster vaccine, and those in the trial cohort who were vaccinated at 24 months of age only. The probability of type 1 diabetes was estimated using regression analysis assuming that there were no losses to 10 year follow up and no competing risks.SettingFinland (total population 5 million and annual birth rate 1.3%).Subjects128 936 children born from 1 October 1983 to 1 September 1985, and 116 352 children born from 1 October 1985 to 31 August 1987.ResultsNo statistically significant difference was found at any time during the 10 year follow up in the risk of type 1 diabetes between the children born before the vaccination period and those vaccinated at the age of 24 months only (relative risk 1.01). The difference in the risk between the cohort vaccinated first at the age of 3 months and the cohort vaccinated at the age of 24 months only was not statistically significant either (1.06).ConclusionIt is unlikely that H influenzae type b vaccination or its timing cause type 1 diabetes in children.

Key messages

• The gradual increase in vaccination programmes does not permit any particular one to be pinpointed as being responsible for the increase in type 1 diabetes in Finland
• There is no difference in the risk of type 1 diabetes between children not vaccinated against H influenzae type b and those vaccinated at the age of 24 months only
• The difference in risk between children vaccinated against H influenzae type b at the age of 3 months and those vaccinated at the age of 24 months was not statistically significant
• It is very unlikely that H influenzae type b vaccination or its timing causes type 1 diabetes in Finnish children

     

Evidence for covalent attachment of phospholipid to the capsular polysaccharide of Haemophilus influenzae type b.

Cells of Haemophilus influenzae type b were grown in a liquid medium containing [3H]palmitate or [14C]ribose or both for two generations of exponential growth. Radiolabeled type-specific capsular polysaccharide, polyribosyl ribitol phosphate (PRP), was purified from the culture supernatant by Cetavlon precipitation, ethanol fractionation, and hydroxylapatite and Sepharose 4B chromatography. The doubly labeled ( [3H]palmitate and [14C]ribose) PRP preparation was found to coelute in a single peak from a Sepharose 4B column, suggesting that both precursors were incorporated into the purified PRP. A singly labeled ( [3H]palmitate) purified PRP preparation was found to be quantitatively immune precipitated by human serum containing antibody against PRP. The radioactivity of this preparation could not be dissociated from PRP by treatment with chloroform-methanol, 6 M urea, sodium dodecyl sulfate, or Zwittergent. Only after acid, alkaline, or phospholipase A2 treatment of PRP labeled with [3H]palmitate or [3H]palmitate and [14C]ribose followed by chloroform-methanol extraction could most of the 3H-radioactivity be recovered in the organic phase. The chloroform-soluble acid-hydrolyzed or phospholipase A2-treated product was identified as palmitic acid after thin-layer chromatography. These results strongly suggest that a phospholipid moiety is covalently associated with the H. influenzae type b polysaccharide PRP.     

Involvement of phospholipid end groups of group C Neisseria meningitidis and Haemophilus influenzae type b polysaccharides in association with isolated outer membranes and in immunoassays.

There are several bacterial polysaccharides (PSs) which contain a terminal lipid moiety. It has been postulated that these terminal lipid moieties anchor the PSs to the outer membrane of the bacteria. Our studies have shown that incubation of native PS from group C Neisseria meningitidis or Haemophilus influenzae type b with isolated outer membrane vesicles results in association of a portion of the PS with the vesicles. Removal of the terminal lipid from the PS by treatment with phospholipase A2 or phospholipase D eliminates this association. In other studies, it was shown that delipidated PSs are not suitable as solid-phase antigens in a currently used enzyme-linked immunosorbent assay (ELISA). Measurement of antibody units in the reference sera by using delipidated PSs as antigens in an ELISA yielded negligible absorbance compared with native PSs when methylated human serum albumin was used to coat the PSs to the plate. Nevertheless, phospholipase A2 and phospholipase D treatment did not noticeably affect antigenic epitopes, since soluble group C PS without the terminal lipid bound antibody as effectively as the native PS did, as measured by a competitive inhibition assay. Both hydrophobic and electrostatic interactions are important for the binding of group C N. meningitidis PS to the ELISA plate, while charge interactions seem to be sufficient for binding the more negatively charged H. influenzae type b PS.     

Surface antigens of Haemophilus influenzae non-typed strains

H. influenzae non-typed strains cause diseases of respiratory organs, otitis, sinusitis and conjunctivitis. H. influenzae surface antigens play an important role in the vital activity of bacteria and the pathogenesis of diseases. A large number of antigens with similar functions and different structure, as well as the variability of their structure, determine the strain specificity of immune response and facilitate the development of chronic diseases. Modern data on the structure and functions of surface antigens of H. influenzae non-typed strains are presented.     

Architecture and adhesive activity of the Haemophilus influenzae Hsf adhesin

Haemophilus influenzae type b is an important cause of meningitis and other serious invasive diseases and initiates infection by colonizing the upper respiratory tract. Among the major adhesins in H. influenzae type b is a nonpilus protein called Hsf, a large protein that forms fiber-like structures on the bacterial surface and shares significant sequence similarity with the nontypeable H. influenzae Hia autotransporter. In the present study, we characterized the structure and adhesive activity of Hsf. Analysis of the predicted amino acid sequence of Hsf revealed three regions with high-level homology to the HiaBD1 and HiaBD2 binding domains in Hia. Based on examination of glutathione S-transferase fusion proteins corresponding to these regions, two of the three had adhesive activity and one was nonadhesive in assays with cultured epithelial cells. Structural modeling demonstrated that only the two regions with adhesive activity harbored an acidic binding pocket like the binding pocket identified in the crystal structure of HiaBD1. Consistent with these results, disruption of the acidic binding pockets in the adhesive regions eliminated adhesive activity. These studies advance our understanding of the architecture of Hsf and the family of trimeric autotransporters and provide insight into the structural determinants of H. influenzae type b adherence.     

KCl-Extractable surface antigens of Schistosoma mansoni: immunological characterization and applicability in immunodiagnosis

A Schistosoma mansoni antigen preparation was obtained by extraction of adult worms with a 3 M KCl solution. An indirect immunofluorescence reaction on cryostat sections of adult worms showed that the extracted antigens mainly originated from the tegument. The complex antigenic composition of the tegument extract was shown by immunoelectrophoresis against serum from infected mice and immunized rabbits, which gave up to 9 and 17 precipitation lines, respectively. When we compared the use of adult worm antigens and the tegument antigen preparation in the DASS and ELISA tests for immunodiagnosis of human schistosomiasis, the average sensitivity of the tests with the two preparations was about equal, although considerable differences between individual sera occurred. Analysis of tegument antigens, fractionated by gel filtration, showed that the main serological activity of the tegument antigen preparation was due to high molecular weight antigens.     

In vivo human immune response to transferrin-binding protein 2 and other iron-regulated proteins of Neisseria meningitidis

Abstract When grown under iron restriction, Neisseria meningitidis expresses new outer-membrane proteins, some of which are antigenic and potentially useful as vaccine components. This is particularly relevant to N. meningitidis serogroup B, against which neither polysaccharide nor conjugate vaccines are effective. We investigated recognition of N. meningitidis serogroup B outer-membrane antigens by three sera from patients recovered from meningitis. Recognition of antigens from the homologous strain provided information on in vivo expression during infection and immunogenicity, while cross-reactivity with outer membrane proteins from the other two strains and from another five strains in our collection allowed evaluation of antigenic heterogeneity. Our results demonstrate that transferrin-binding protein 2 (TBP2) is immunogenic in humans, to varying degrees depending on the strain, and that TBP2s (like the equivalent proteins of Haemophilus influenzae type b) are among the most important iron-regulated outer membrane antigens expressed during infection. Other immunogenic outer membrane proteins (some iron-regulated) are also expressed during infection; in a previous study in mouse, three of these proteins (with M _r of 50, 70 and 77 kDa) did not induce an immune response. Our cross-reactivity data provide some support for Robki et al.'s two-group classification of N. meningitidis strains, and provide evidence against the possibility that the antigenic domains shared by the TBP2s of all N . meningitidis strains induce immune responses in vivo.     

Candidate vaccine antigens and genes in Pasteurella multocida.

Pasteurella multocida is the causative agent of fowl cholera and other diseases of production animals. Isolates are classified into five groups based on capsular antigens and into 16 serotypes based on LPS antigens. Strains causing fowl cholera are most frequently designated A:1, A:3 or A:4. Whole cell bacterins can provide some degree of protection, but only against the homologous LPS serotype. There is good evidence that cross-protective antigens are expressed only under in vivo conditions. Empirically derived, live, attenuated vaccines can protect against heterologous serotypes, but because the basis for attenuation is undefined, reversion to virulence is not uncommon. Work in our laboratory is aimed at using a variety of approaches to identify potential protective antigens or virulence genes to be used as candidates for attenuating mutations or as the basis for vaccine antigen delivery systems. The gene encoding an outer membrane protein, Oma87, which is a homologue of the D15 protective antigen of Haemophilus influenzae, was cloned and sequenced. Rabbit antiserum prepared against recombinant Oma87 could passively protect mice against infection. Type 4 fimbriae form the basis of vaccines against ovine footrot and bovine keratoconjunctivitis. We have identified type 4 fimbriae on the surface of P. multocida, purified the fimbrial subunit protein, PtfA, and determined its N-terminal amino acid sequence. Subsequent cloning of the ptfA gene and its inactivation will now be used to assess the importance of type 4 fimbriae in virulence. There has long been anecdotal evidence for the importance of capsule in virulence, but unequivocal genetic evidence for such a role is lacking. We have cloned and characterised the capsule biosynthetic locus in P. multocida A:1 and identified four bex genes involved in capsule transport and genes encoding enzymes involved in the biosynthesis and transfer of the N-acetyl glucosamine and glucuronic acid components of the capsule. It has been suggested that the low concentration of available iron in vivo acts as an environmental cue for expression of cross-protective antigens. Accordingly, we have cloned and characterised the gene encoding transferrin binding protein, Tbpl, so that its role in immunity and virulence can be investigated. Although P. multocida is not normally considered haemolytic, we have observed haemolysis under anaerobic conditions. Standard library construction and screening resulted in the identification of the mesA gene which encodes an esterase enzyme resulting in a haemolytic phenotype under anaerobic conditions. Virulence studies with mesA- mutants were performed to assess its role in pathogenesis. Using a promoterless phoA gene vector system, the cloning of proteins homologous to known surface proteins of other species as well as proteins unique to P. multocida, allowing their potential as vaccine components to be assessed.     

Lipoproteins of Haemophilus influenzae type b.

Haemophilus influenzae type b Minn A produced 12 lipoproteins with apparent molecular weights of between 14,000 and 67,000. The lipoproteins were identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and fluorography of delipidated extracts of cells grown in [3H]palmitate. When the delipidated cell extracts were subjected to acid methanolysis, tritium was quantitatively recovered as palmitate and methyl palmitate, indicating that the [3H]palmitate had not been degraded and reincorporated into nonlipid material during cell growth. One of the lipoproteins comigrated with outer membrane protein (OMP) P6. OMP P6 was purified from [3H]palmitate-labeled cells. The purified protein preparation contained both amide- and ester-linked fatty acids. We conclude that (i) H. influenzae type b produces several lipoproteins, and (ii) one of these lipoproteins is OMP P6, a protein under consideration as a vaccine component.     

Mouse models of infection for Neisseria meningitidis B,2b and Haemophilus influenzae type b diseases

A disseminated and fatal infection was established in C57BL mice, injected intraperitoneally with either Neisseria meningitidis B,2b or Haemophilus influenzae type b bacteria plus enhancement factors. The effects of mucin, hemoglobin, and iron dextran as enhancement of bacterial infectivity in mice were evaluated individually and in combination. A mixture of mucin and hemoglobin was most effective in enhancing the virulence of the pathogens. Inbred mouse lines were more susceptible than outbred ones. Relative virulence of a number of bacterial strains was also compared in one selected mouse line. Neisseria meningitidis B,2b and Haemophilus influenzae type b strains were more virulent than non-B,2b and nontypable strains. Finally, the course of bacteremia for the two infections in mice was followed by quantitative blood cultures. The animals succumbed to the generalized condition within 72 h. In the case of Neisseria meningitidis B,2b, 10 organisms with 4% mucin and 1.6% hemoglobin were sufficient to kill 50% of the animals. For Haemophilus influenzae type b, 300 bacteria with 5% mucin and 2% hemoglobin were necessary to obtain similar effects.     

Diversity of the outer membrane protein P2 gene from major clones of Haemophilus influenzae type b

In previous studies, it has been demonstrated that outer membrane protein P2 from Haemophilus influenzae type b has porin activity and that antibody directed against P2 is protective in an infant rat bacteraemic model. Outer membrane protein subtyping has been employed to subclassify type b Haemophilus isolates. Strain MinnA has the outer membrane protein subtype 1H and is representative of the dominant clonal group of disease-producing isolates in the United States. In the present study, the P2 gene from strain MinnA was employed to probe EcoRI- and Pvull-digested chromosomal DNA from 24 Haemophilus influenzae type b isolates representative of the common outer membrane protein subtype groups observed throughout the world. Restriction fragment length polymorphisms were identified for the members of the outer membrane protein subtype 3L group, but not for the other subtypes examined. The P2 gene from each of four prototype isolates was then cloned, sequenced and compared to the previously reported sequence of the strain MinnA gene. The P2 gene from each of two isolates with the outer membrane protein subtype 3L was identical to the MinnA P2 sequence. The P2 gene from a subtype 2L isolate differed by a single nucleotide and the gene from a subtype 6U isolate differed by 13 nucleotides. Thus, the P2 protein is highly conserved among type b isolates.     

Overview of recent clinical trials of acellular pertussis vaccines.

The evidence from pre-licensure studies does not suggest that there are clinically important differences in reactogenicity between acellular vaccines. The merits of different acellular products will therefore have to be compared on efficacy criteria. Ideally, acellular vaccines with the minimum antigen content necessary to ensure optimum protection should be used in order to avoid administration of superfluous antigens to children and to simplify licensing and batch release procedures.On the basis of the evidence so far available it seems unlikely that monocomponent pertussis toxin (PT) vaccines provide optimal protection and that multicomponent vaccines are needed to achieve a level of disease control that approaches that of a good whole-cell vaccine. It is unclear whether all two component vaccines containing PT and filamentous haemagglutinin (FHA) have similar efficacy but on the available evidence the safest option for policy makers would seem to be to use a vaccine with at least three components, PT+FHA+pertactin. There is now good evidence that the five component vaccine which contains agglutinogens 2 and 3 in addition to PT/FHA and pertactin provides the best protection and is the only acellular vaccine whose efficacy matches that of a good whole cell vaccine. However, the public health advantage of the five component vaccine over other acellular vaccines may not become apparent until they have been in routine use for some decades and their ability to protect against transmission as well as clinical pertussis has emerged.The decision to replace an effective whole-cell vaccine by an acellular vaccine for primary immunisation needs careful consideration. Apart from the probable sacrifice of efficacy for reduced reactogenicity (at least for vaccines which do not contain agglutinogens 2 and 3) there is the question of value for money and the ease with which acellular DTP vaccines can be combined with conjugate polysaccharide vaccines such as Haemophilus influenzae type b.Whatever the decision of policy makers, the need for continued follow up of trial cohorts and active surveillance of the efficacy and safety of those acellular vaccines that are introduced into routine use must be accorded a high priority.     

Relationship of the sensitizing and protective properties of pertussis antigens

When comparing delayed hypersensitivity (DN) to B. pertussis corpuscular antigens with the agglutinogenic composition of B. pertussis, as well as to its histamine-sensitizing, leukocyte-sensitizing, adjuvant and hemagglutinating activity, no correlation was detected between the specific sensitizing properties of these antigens and the serotype and studied nonspecific properties of B. pertussis. The DH level correlated with the protective activity of B. pertussis corpuscular antigens and the ultrasonic fractions of B. pertussis. The close correlation of these two phenomena suggest that DH-inducing and protective B. pertussis antigens are identical, though their action has different manifestations, depending on the method of administration of the antigen preparation. On these grounds a new method for evaluating the immunogenicity of B. pertussis antigens is proposed. This method consists in comparing the sensitizing activity of the antigen under test and that of the national standard.     

Regulation of three forms of cytochrome P-450 and epoxide hydrolase in rat liver microsomes. Effects of age, sex, and induction

A procedure for the preparation of monospecific antibody directed against rat liver microsomal cytochrome P-45-a is described. This antibody, together with monospecific antibodies to cytochromes P-450b and P-450c, has been used to show that these three forms of cytochrome P-450 are distinct and share no common antigenic determinants. These antibodies (a) give single immunoprecipitin bands with detergent-solubilized microsomes; (b) do not cross-react with the purified heterologous antigens in Ouchterlony double diffusion analyses; (c) have no effect on catalytic activity of the heterologous antigens but completely inhibit the enzymatic activity of the homologous antigens; and (d) remove only the homologous antigen from detergent-solubilized microsomes when covalently bound to a solid support. With radial immunodiffusion assay, we have quantitated these three forms of cytochrome P-450 in liver microsomes after treatment of rats with seven different inducers of cytochrome P-450. The levels of these cytochrome P-450 isozymes vary independently and are also regulated by the age and sex of the animal. The antibodies have also been used to assess the contribution of cytochromes P-450a, P-450b, and P-450c in the metabolism of xenobiotics by rat liver microsomes. A large proportion of benzo(a)pyrene metabolism and testosterone 16 alpha-hydroxylation in microsomes from untreated rats is not catalyzed by cytochromes P-450a, P-450b, and P-450c. Epoxide hydrolase, another microsomal enzyme involved in the metabolism of xenobiotics, was also quantitated by radial immunodiffusion after prior treatment of rats with microsomal enzyme inducers. The inductions of epoxide hydrolase varies independently of the induction of cytochromes P-450a, P-450b, and P-450c.     

Serological analysis and pathogenic potentials of Wangiella dermatitidis isolated from bats

Methods for the preparation of antigens from clinically isolated cultures of Aspergillus were standardized. Sera from 25 suspected cases of pulmonary aspergillosis were tested against antigens prepared by us, from 4 strains of A. fumigatus and one strain of A. flavus, using the Ouchterlony double diffusion and immunoelectrophoretic techniques.Of the 25 sera tested, 18 reacted positively with antigens of A. fumigatus, one with A. flavus and 2 with both these species. Antigens of two non-pathogenic Aspergilli included in the study failed to react with any of the sera. Our antigen preparations gave more numerous as well as sharper precipitin lines than the commercial Bencard antigens which were used for comparison. Moreover, mycelial antigens from 48 to 96 h old cultures revealed precipitin lines comparable to that of the routine, 4 week old culture filtrate antigens, thus suggesting that the incubation period for obtaining antigens could be cut down considerably.Memoir No. 323 from the Centre of Advanced Study in Botany.Deceased     

Acid phosphatase activity as a measure of Haemophilus influenzae adherence to mucin

Haemophilus influenzae is an important respiratory tract pathogen. Toward understanding the progression of H. influenzae from commensal to pathogen, we need to understand the steps of colonization and infection, processes which must involve overcoming the normal host mucociliary clearance mechanism. A reliable method for the screening and quantitation of mucin-H. influenzae binding to allow for the assessment of the physiological variables significant to H. influenzae-mucin interactions in the normal and diseased conditions, will provide insight on how to intervene to prevent, inhibit, or treat infection. The current methods for enumeration of mucin-bound H. influenzae are labor intensive and rely on viable organisms. In this report, we present a new detection method, which reduces the number of variables, processing steps, and time involved, providing an economical, rapid, and reliable means to screen for and quantitate mucin-bound H. influenzae. Organisms are applied to mucin-coated microtiter wells for a set time; nonadherent organisms are removed with gentle rinses; wells are incubated with the phosphomonoesterase substrate p-nitrophenyl phosphate; and the absorbance, reflecting phosphatase activity of the mucin-bound organisms, is read at 410 nm in a microtiter plate reader against enzymatic activity calibration curves. All nonencapsulated and encapsulated H. influenzae tested exhibited significant acid phosphate activity within 20 min, which provided linear relationships with the numbers of organisms present. H. influenzae mucin binding characteristics obtained by this method were generally comparable to published data, and ranged from 10(3) to 10(6) organisms per well, depending on both strain of organism and type of mucin employed. This convenient, rapid and economical mucin adherence assay, will enable more extensive and comprehensive studies of the interactions of H. influenzae adhesins and specific ligands on mucin macromolecules, as well as the nonspecific means by which mucins function in preventing bacterial infection.     

Prospective study of bacterial meningitis in North East Thames region, 1991-3, during introduction of Haemophilus influenzae vaccine.

OBJECTIVE--To describe the epidemiology of primary bacterial meningitis in the North East Thames region over a three year period before and during the introduction of the vaccine for Haemophilus influenzae type b. DESIGN--Analysis of information on cases of primary bacterial meningitis identified by microbiology laboratories in the region, with collection of case data by questionnaire. MAIN OUTCOME MEASURES--Annual incidence rates for types of meningitis according to age and ethnic group. RESULTS--The annual incidence rates for the three major causes of bacterial meningitis in the general population were 1.9/100,000 for Neisseria meningitidis, 1.6/100,000 for Haemophilus influenzae before vaccination, and 1.0/100,000 for Streptococcus pneumoniae. Higher rates of H influenzae meningitis were found in Asians compared with white people (3.6/100,000 v 1.5/100,000, P = 0.01). As a result of the vaccine programme introduced in October 1992 the number of cases of H influenzae meningitis in children under 5 years has fallen by 87%. CONCLUSIONS--Bacterial meningitis is a serious problem especially in preschool children. There are differences in the incidence of some causes of bacterial meningitis in different ethnic groups; with H influenzae type b being significantly more common among black and Asian people than among white people. The immunisation programme for H influenzae type b in the North East Thames region has been successful in reducing the incidence of this type of meningitis in Asian and white populations. The numbers were too small to evaluate in the black population.