Relationship of Serogroups of Neisseria meningitidis I. Microagglutination, Gel Diffusion, and Slide Agglutination Studies of Meningococcal Antisera Before and After Absorption with RAS-10 Strain of Meningococci

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)

Influence of nutrient limitation and low pH on serogroup B Neisseria meningitidis capsular polysaccharide levels: correlation with virulence for mice

Neisseria meningitidis strain M986, which possesses a polyanionic sialic acid capsular polysaccharide, was resistant to the bactericidal effects of normal rabbit serum, but sensitive when immune serum and complement were present. An isogenic strain PRM102, deficient in the ability to produce capsular polysaccharide, was sensitive to normal serum. Strain M986, when grown under conditions of low pH or nutrient limitation, synthesized increased levels of capsular polysaccharide. This was accompanied by an increase in cell surface hydrophilicity and virulence for mice. Cells grown in low-pH, iron-limited medium synthesized the highest concentration of polysaccharide and exhibited the highest cell surface hydrophilicity and virulence among the cases examined. The increase in capsular polysaccharide was partly explained by a decrease in the specific activity of a membrane-bound cytidine monophosphate-N acetylneuraminic acid hydrolase. The results suggest that conditions of nutrient limitation and low pH exert profound effects on the physicochemical nature of the meningococcal cell surface which, in turn, cumulate in enhanced virulence of this organism for mice.

Meningococcal infections in Scotland 1972-82

Strains of Neisseria meningitidis isolated from patients with meningitis or septicaemia without meningitis in Scotland during the years 1972-82 have been reviewed together with details of the age, sex, disease and outcome of the patients from whom they were isolated. A total of 1185 strains were isolated, of which 927 were examined at the Meningococcal Reference Laboratory (Scotland): 19.3% were of serogroup A, 63% of group B, 9.6% of group C, 6% of W135 and 1.6% of other groups. Non-groupable strains were rare. Disease was most common in the first years of life but there was a difference in the age distribution of disease due to the different serogroups, the proportion of disease due to group B being smaller in adults than that due to other serogroups. The overall mortality in meningitis was 7.5% and in septicaemia was 20.6%, although there were differences between the rates for the various serogroups. The serogroup distribution differed in disease as opposed to meningococci isolated from carriers although group B strains were predominant in both series. Overall, approximately 15% of strains were resistant to sulphadiazine, the proportion of resistant group A strains being higher than that of other serogroups.

Clinical evaluation of the rapid carbohydrate degradation microtube method for identification of Neisseria species

The rapid carbohydrate degradation (Carr Microbiologicals Wichita, Kans.) microtube method is a new test system designed for the identification of Neisseria spp. The system consists of four microtubes containing different carbohydrates in a peptone-Bitone basal medium. This method was evaluated for accuracy and speed in identifying species of Neisseria. Of the 386 clinical isolates used in this study, 98.4% were correctly identified to species level in 4 h with the rapid carbohydrate degradation system; parallel testing of the same isolates with conventional cystine-tryptic agar resulted in 96.1% accuracy in 48 h.

Evaluation of rapid carbohydrate degradation tests for identification of pathogenic Neisseria

A total of 156 clinical isolates were tested by the modified rapid fermentation test, the BACTEC Neisseria differentiation kit, and the cystine-Trypticase agar method. The modified rapid fermentation test and BACTEC methods accurately identified at least 95% of 101 strains of N. gonorrhoeae tested and at least 91% of 45 strains of N. meningitidis tested within 4 h. Overall, the cystine-Trypticase agar method was the most accurate (97%) but required as long as 48 h of incubation. The data presented appear to show that rapid carbohydrate degradation tests can provide reliable and specific identification results.

Serogroup identification of Neisseria meningitidis: comparison of an antiserum agar method with bacterial slide agglutination

A serum agar method for serogrouping Neisseria meningitidis is described and compared with conventional bacterial slide agglutination. There was 93% agreement for 300 strains examined individually by each method. Among strains from serogroups A, B, C, Y, and W135, there was 100% correlation, whereas strains from serogroup 29E (Z') had only 67% correlation. The serum agar method was rapid, as well as easy to perform and interpret. The potential benefits of this method for epidemiological studies and reference laboratories processing large numbers of meningococcal isolates are emphasized.

Protection Against Meningococcal Challenge Afforded Mice After Immunization with Typhoid-Paratyphoid Vaccine USP

Mice immunized with typhoid-paratyphoid vaccine USP were found to be protected when challenged with serological groups A, B, and C of Neisseria meningitidis . Mice immunized with this vaccine both 14 and 7 days prior to challenge were protected against mean lethal doses (LD 50 ) of 5,220 and 1,151 of groups A and B, respectively, and in two separate experiments they were protected against 3,568 and 268 LD 50 of group C. Mice immunized four or more times on successive days prior to challenge were also protected. They demonstrated tolerance and survived a much larger LD 50 challenge than mice immunized by any other immunization schedule. Mice immunized once or twice anytime within 7 days prior to challenge were not protected and thus failed to exhibit nonspecific resistance. Serum antibody probably was responsible for the protection afforded mice immunized 14 and 7 days prior to challenge. However, this was not demonstrated conclusively.

Hemagglutination inhibition for serogrouping of Neisseria meningitidis

A hemagglutination inhibition (HI) test has been studied as an alternative to bacterial agglutination (BA) for serogrouping strains of Neisseria meningitidis isolated from clinical specimens. The HI test consists of polysaccharide antigens adsorbed to sheep red blood cells which were then agglutinated by group-specific antisera. Supernatant fluids from suspensions of meningococci were used to inhibit the agglutination. Results of the two tests agreed for 381 (80%) carrier strains. Of the remaining 95 strains, 82 (86%) were identified by HI although they were nongroupable by BA. Thus, the HI test has been shown to be more highly specific and sensitive and to be more economical of reagents and time than the BA test.

Relationship of serogroups of Neisseria meningitidis. II. R variants of Neisseria meningitidis

Meningococci isolated in primary cultures from nasopharyngeal carriers occasionally consisted of mixtures of smooth (S) and rough (R) strains. The R strains were separated from the S strains and their morphological and serological characteristics were studied. Some of these R strains reverted spontaneously to S strains which subsequently produced group-specific polysaccharide. Several R strains, grown in the presence of deoxyribonucleic acid from either an R strain of known parentage or an S strain, formed recombinants with serological group specificity.

Carbohydrate fermentation patterns of Neisseria meningitidis determined by a microtiter method

A carbohydrate fermentation technique has been developed and compared to the standard fermentation test with cystine-Trypticase-semisolid agar for the identification of Neisseria meningitidis. This new method utilizes Mueller-Hinton broth as a basal substrate and is performed with microtiter methods. By using Mueller-Hinton broth with and without the addition of antibiotics, the method can be adjusted to test the fermentation patterns of all of the Neisseria including N. gonorrhoeae.