Characterization of Neisseria meningitidis serogroup A strains from an outbreak in France by serotype, serosubtype, multilocus enzyme genotype and outer membrane protein pattern

[Meningococci throughout the world : Phenotypic and molecular markers.]

The first markers of meningococci were serogroup, defined by different polyosidic capsular immunospecifities (12 are described at present), and are still of great importance. Several other antigenic structures such as outer membrane proteins (OMPs) are used as markers : OMP serotypes of classes 2 and 3, OMP subtype of class 1. Serogroups, serotypes, subtypes and sometimes immunotypes (based on LPS) are associated in an antigenic formula (AF). At a world-wide level, the Electrophoretic Type (ET) defined by Multilocus Enzyme Electrophoresis (MLEE) is the most useful marker. For instance, the ET-5 and ET-37 have been described. The ET-5 was constituted primarily, but not exclusively, by strains of AF:B:15:P1.7,16 and B:4:P1.15. The ET-37 was constituted mostly by strains C:2a:P1.2,5. Two pandemics were due to Neisseria meningitidis serogroup A. They were mainly defined by MLEE. The first began in China in 1966, crossed Europe, and ended in Brazil in 1974 where it was responsible for a particularly widespread outbreak. The second pandemic, due to the same epidemic invasive strain A:4:P1.9/clone III-1 also began in China in 1983, spreading through Nepal, northern India. It was responsible for a severe oubreak in Mecca in August of 1987. It spread all around the world when the pilgrims returned to their countries. In countries with adequate health care facilities, the pandemic was stropped within two or three weeks. Unfortunately, in countries without these health care facilities, the spreading continues. For instance in Africa, specifically Niger, strains of this type continued to be isolated through the beginning of 1996. Molecular epidemiology markers like pulsotype and ribotype for instance, are able to demonstrate genetic variability between strains.

Global epidemiology of meningococcal disease

As reviewed in this paper, meningococcal disease epidemiology varies substantially by geographic area and time. The disease can occur as sporadic cases, outbreaks, and large epidemics. Surveillance is crucial for understanding meningococcal disease epidemiology, as well as the need for and impact of vaccination. Despite limited data from some regions of the world and constant change, current meningococcal disease epidemiology can be summarized by region. By far the highest incidence of meningococcal disease occurs in the meningitis belt of sub-Saharan Africa. During epidemics, the incidence can approach 1000 per 100,000, or 1% of the population. Serogroup A has been the most important serogroup in this region. However, serogroup C disease has also occurred, as has serogroup X disease and, most recently, serogroup W-135 disease. In the Americas, the reported incidence of disease, in the range of 0.3-4 cases per 100,000 population, is much lower than in the meningitis belt. In addition, in some countries such as the United States, the incidence is at an historical low. The bulk of the disease in the Americas is caused by serogroups C and B, although serogroup Y causes a substantial proportion of infections in some countries and W-135 is becoming increasingly problematic as well. The majority of meningococcal disease in European countries, which ranges in incidence from 0.2 to 14 cases per 100,000, is caused by serogroup B strains, particularly in countries that have introduced serogroup C meningococcal conjugate vaccines. Serogroup B also predominates in Australia and New Zealand, in Australia because of the control of serogroup C disease through vaccination and in New Zealand because of a serogroup B epidemic. Based on limited data, most disease in Asia is caused by serogroup A and C strains. Although this review summarizes the current status of meningococcal disease epidemiology, the dynamic nature of this disease requires ongoing surveillance both to provide data for vaccine formulation and vaccine policy and to monitor the impact of vaccines following introduction.

Quadrivalent meningococcal ACYW-135 glycoconjugate vaccine for broader protection from infancy

Invasive meningococcal disease is a global public-health concern, with infants and adolescents bearing the majority of the disease burden. Vaccination is the most rational strategy to prevent meningococcal disease. Control of serogroup C disease has largely been achieved by the introduction of glycoconjugate meningococcal C vaccines, initially in the UK in 1999, and subsequently in several other countries. The recent licensure of a quadrivalent glycoconjugate vaccine against serogroups A, C, Y and W-135 in the USA and Canada has broadened protection against Neisseria meningitidis in 2-55 year olds. The investigational quadrivalent meningococcal serogroup A, C, Y and W-135 glycoconjugate vaccine (MenACYW-CRM197), which is immunogenic from infancy, has the potential to extend protection to the most vulnerable age group. This article discusses this novel quadrivalent vaccine formulation and its potential to control invasive disease caused by N. meningitidis serogroups A, C, Y and W-135.

Prospects for vaccine prevention of meningococcal infection

Neisseria meningitidis is the leading cause of bacterial meningitis in the United States and worldwide. A serogroup A/C/W-135/Y polysaccharide meningococcal vaccine has been licensed in the United States since 1981 but has not been used universally outside of the military. On 14 January 2005, a polysaccharide conjugate vaccine that covers meningococcal serogroups A, C, W-135, and Y was licensed in the United States for 11- to 55-year-olds and is now recommended for the routine immunization of adolescents and other high-risk groups. This review covers the changing epidemiology of meningococcal disease in the United States, issues related to vaccine prevention, and recommendations on the use of the new vaccine.

Molecular epidemiology of serogroup a meningitis in Moscow, 1969 to 1997

Molecular analysis of 103 serogroup A Neisseria meningitidis strains isolated in Moscow from 1969 to 1997 showed that four independent clonal groupings were responsible for successive waves of meningococcal disease. An epidemic from 1969 to the mid-1970s was caused by genocloud 2 of subgroup III, possibly imported from China. Subsequent endemic disease through the early 1990s was caused by subgroup X and then by subgroup VI, which has also caused endemic disease elsewhere in eastern Europe. A 1996 epidemic was part of the pandemic spread from Asia of genocloud 8 of subgroup III. Recent genocloud 8 epidemic disease in Moscow may represent an early warning for spread of these bacteria to other countries in Europe.

The 1998 Senegal epidemic of meningitis was due to the clonal expansion of A:4:P1.9, clone III-1, sequence type 5 Neisseria meningitidis strains

Between January and April 1998, a meningitis outbreak due to serogroup A meningococcus took place in Senegal. The outbreak began in Gandiaye, 165 km to the east of Dakar, and progressed towards the towns of Gossas, Niakkhar, Guinguineo, Fatik, Foundiougne, Dioffior, Sokone, Kaolack, and Nioro. At the same time, the outbreak reached regions of Kaffrine, Koungheul, and Tambacounda in the east of Senegal. A total of 1,350 cases and 200 deaths were reported. The WHO Collaborating Center in Marseilles received 24 strains for analysis. All were serogroup A Neisseria meningitidis, type 4 and subtype P1.9. Multilocus enzyme electrophoresis, performed by Institut Pasteur Paris, showed that the strains belonged to clone III-1. DNA restriction fragments generated by endonuclease BglII and analyzed by pulsed-field gel electrophoresis showed 24 indistinguishable fingerprint patterns similar to those of meningococcus strains isolated from African outbreaks since 1988. Three strains were studied by multilocus sequence typing (MLST) with seven loci. The comparison between sequences and existing alleles on the MLST website () allowed us to assign these strains to sequence type 5 (ST5), as their sequences were identical to the consensus at seven loci. All 24 strains were susceptible to penicillin, amoxicillin, chloramphenicol, and rifampin. Subgroup III is finishing its spread towards west of the meningitis belt of Africa. To our knowledge, this is the first time subgroup III, and more precisely ST5, strains are reported as being responsible for a meningitis outbreak in Senegal.

Epidemics of serogroup A Neisseria meningitidis of subgroup III in Africa, 1989-94

A total of 125 strains of Neisseria meningitidis recovered in the course of outbreaks from patients with systemic disease in 11 African countries between 1989 and 1994 were analysed by serogrouping, serotyping and multilocus enzyme electrophoresis. Of the 125 patient strains 115 (92%) belonged to the clone-complex of serogroup A meningococci, designated subgroup III. Among the remaining strains, 4 were also serogroup A, but belonged to the clonal groups I and IV-1 (2 strains each), whilst 6 strains (4 serogroup C and 2 serogroup W135) represented clones of the ET-37 complex. Our results indicated that the second pandemic caused by clones of subgroup III is still spreading in Africa. Towards the West it has reached Niger, Mali, Guinea and The Gambia, and towards the South, the Central African Republic, Uganda, Rwanda, Burundi, Tanzania and Zambia.

Molecular population genetic analysis of emerged bacterial pathogens: selected insights

Research in bacterial population genetics has increased in the last 10 years. Population genetic theory and tools and related strategies have been used to investigate bacterial pathogens that have contributed to recent episodes of temporal variation in disease frequency and severity. A common theme demonstrated by these analyses is that distinct bacterial clones are responsible for disease outbreaks and increases in infection frequency. Many of these clones are characterized by unique combinations of virulence genes or alleles of virulence genes. Because substantial interclonal variance exists in relative virulence, molecular population genetic studies have led to the concept that the unit of bacterial pathogenicity is the clone or cell line. Continued new insights into host parasite interactions at the molecular level will be achieved by combining clonal analysis of bacterial pathogens with large-scale comparative sequencing of virulence genes.

Molecular typing of Neisseria meningitidis serogroup A using the polymerase chain reaction and restriction endonuclease pattern analysis

A new molecular typing method for identification and characterization of Neisseria meningitidis is reported. Chromosomal DNA from 20 well-documented meningococcal strains of serogroup A originating from France, Central African Republic, Sudan and Burkina Faso were amplified using the polymerase chain reaction. Primers designed in this study were located in the pilA/pilB locus which has been shown to be conserved in the genus Neisseria. The amplified fragments were subjected to restriction endonuclease analysis using three different enzymes, and the restriction endonuclease patterns obtained were compared. Clonal isolates clustered together in distinct restriction endonuclease patterns which are described in this study and coincided with electrotypes as determined by multi-locus enzyme electrophoresis. This DNA-based typing system for meningococci may be useful for epidemiological studies.

Characterization of serogroup A Neisseria meningitidis strains by rRNA gene restriction patterns and PCR: correlation with the results of serotyping, subtyping and multilocus enzyme electrophoresis

We studied 35 strains of Neisseria meningitidis serogroup A from different locations (France, Central African Republic, Sudan and Burkina Faso) using both ribotyping and a polymerase chain reaction (PCR). A non-radioactive probe label was used for ribotyping; detection consisted of an immunoenzymatic procedure using a bispecific antibody. The PCR was designed to amplify the 16S-23S rDNA internal transcribed spacer. These techniques were compared with other markers. The strains were identified as belonging to three clones (I, III-1, IV) by multilocus enzyme electrophoresis (MEE) and to three subtypes by serological methods. Ribotyping identified five groups and PCR identified four groups. Ribotyping gave more diversity between strains than either MEE or sero/subtyping, but confirmed the epidemiological data provided by the combination of these two techniques. The PCR provided a simple and convenient one-step procedure for the differentiation of strains of serogroup A.

Serotype and serosubtype distribution of strains of Neisseria meningitidis isolated in South Australia and the Northern Territory of Australia: 1971-1989

Strains of meningococci isolated from patients in South Australia (SA) and the Northern Territory (NT) with either bacteremia or meningitis (or both) were serotyped and serosubtyped using monoclonal antibodies in a whole cell ELISA technique. From SA, 144 isolates were examined for the period 1971 through 1989 and from the NT, 38 isolates from 1975 through 1977 and 1983 through 1989 were examined. During the periods of study the principal serogroups were group B in South Australia and group A in the Northern Territory. About 60% of the SA strains were typable and subtypable: the predominant types were 4, 2a, 15 and 14, in that order; the predominant subtypes were P1.2, P1.1 and P1.10, in that order. Of the strains from the NT about 80% were typable, the predominant type was type 4 and all 19 group A strains were identified as type 4, subtype P1.10.

Characteristics of serogroup A Neisseria meningitidis strains isolated in the Central African Republic in February 1992

A severe epidemic of serogroup A meningococcus meningitis occurred in the northwest Central African Republic from January to March 1992. Strains from 24 patients were characterized using serotyping, testing of susceptibility to antibiotics, and multilocus enzyme electrophoresis. In 23 of the 24 patients the causal strain was found to be 4:P1.9/clone III-1. These results indicate that such strains continue to spread in Africa and have taken hold in areas outside the "meningitis belt." This may be a consequence of changing climatic conditions.

Clonal spread of serogroup A meningococci: a paradigm for the analysis of microevolution in bacteria

Extensive epidemiological analyses of epidemics of meningococcal meningitis have resulted in large, well-defined strain collections which represent the local diversity and global spread of serogroup A bacteria. Several genes for cell surface proteins are conserved during spread, with a few exceptions: analysis of these exceptions has revealed some of the phenomena which can lead to microevolution. Microevolution is so rapid with serogroup A meningococci that several independent recombination events have been documented within the last few decades. In a few cases, the recombinant bacteria have become established by clonal replacement plus epidemic spread. Comparison with other bacteria indicates that serogroup A meningococci provide a number of advantages for analysis of microevolution.

Immunogenicity and evolutionary variability of epitopes within IgA1 protease from serogroup A Neisseria meningitidis

Five murine epitopes were defined and mapped within IgA1 protease produced by Neisseria meningitidis. Epitopes 1 and 2 were present in IgA1 protease from all strains, and from Neisseria gonorrhoeae. Epitopes 3 through to 5 varied between subgroups of serogroup A meningococci, but have remained constant over decades within the subgroups, except for epitope 4, which changed between 1983 and 1987 during the spread of subgroup III meningococci from Asia to Africa. Binding of monoclonal antibodies to epitopes 1, 4 and 5 neutralized enzymatic function. Human sera containing antibodies to IgA1 protease as a result of natural infection inhibited binding of monoclonal antibodies to epitope 4 but not to the other epitopes.

Characterization of Neisseria meningitidis by polymerase chain reaction and restriction endonuclease digestion of the porA gene

Subtype classification based on the use of monoclonal antibodies to the class 1 outer membrane protein combined with techniques such as multilocus enzyme electrophoresis remains the standard method of characterizing isolates during outbreaks of invasive meningococcal disease. We developed a rapid typing method based on the restriction fragment length polymorphisms (RFLPs) within the polymerase chain reaction (PCR) product of the porA gene, which encodes the class 1 outer membrane protein, reflecting genotypic rather than phenotypic variability between strains. Forty-five isolates of invasive Neisseria meningitidis obtained from October 1990 to April 1992 were studied after randomization and coding. Included among these were isolates from a local outbreak that resulted in a mass vaccination program. PCR amplification for each isolate was followed by restriction digestion with the following enzymes in the indicated sequence: HaeIII, RsaI, HinfI, HpaII, and AluI. Eighteen different patterns were demonstrated on the basis of RFLPs, whereas only seven groups were identified after standard subtyping. The most common isolate identified by serosubtyping was serogroup C, serotype 2a, subtype P1.2 (C:2a:P1.2) (38%). Thirteen (76%) of these group C isolates shared a common RFLP pattern after digestion with the five restriction enzymes. We were able to further differentiate strains of C:2a:P1.2 with electrophoretic type 5 from electrophoretic types 1, 9, and 15 that occurred during an apparent outbreak. We were also able to characterize 15 isolates (33%) which could not be subtyped with monoclonal antibodies. Our method offers a convenient alternative to standard subtyping procedures and is particularly useful in outbreak situations in which rapid characterization of N. meningitidis is essential so that rational public health policy regarding preventative measures can be formulated.

Clonal and antigenic analysis of serogroup A Neisseria meningitidis with particular reference to epidemiological features of epidemic meningitis in the People's Republic of China

Representative strains of serogroup A Neisseria meningitidis were chosen from all major meningitis epidemics worldwide since 1960 and subjected to analysis for the electrophoretic variation of 15 cytoplasmic allozymes and four outer membrane proteins. The 290 strains defined 84 unique electrophoretic types which were classified in nine subgroups. Tests with monoclonal antibodies specific for conserved pilin epitopes showed that the class I, IIa, and IIb epitopes were uniform within the subgroups. Similarly, the subgroups were uniform for expression of different variable regions of class 1 outer membrane protein, with a few minor exceptions. Many of the bacteria tested were isolated in the People's Republic of China, and the epidemiology of Chinese epidemics of meningococcal meningitis is described. The analysis approaches a global description of epidemic meningitis caused by serogroup A meningococci in the past 30 years.

Neisseria spp. and AIDS

Neisseria meningitidis from various serogroups and two commensal neisseriae (N. sicca and N. perflava) were isolated from 15 patients at various stages of human immunodeficiency virus infection in this clinical and bacteriological study. The cases were grouped into the following three classes: (i) infections with an N. meningitidis strain of a serogroup known to be pathogenic (A, B, or C) and apparently independent of the human immunodeficiency virus infection, (ii) infections with a N. meningitidis strain of a serogroup which is normally either commensal or poorly pathogenic (serogroups Y, X, Z, and Z,29E), (iii) pulmonary and disseminated infections occurring in the course of the clinical evolutionary stage of AIDS, in two cases of which commensal neisseriae (N. sicca and N. perflava) were isolated from blood cultures.