Clonal groupings in serogroup X Neisseria meningitidis. (Research).The genetic diversity of 134 serogroup X Neisseria meningitis isolates from Africa, Europe, and North America North America, third largest continent (1990 est. pop. 365,000,000), c.9,400,000 sq mi (24,346,000 sq km), the northern of the two continents of the Western Hemisphere. was analyzed by multilocus sequence typing Multilocus sequence typing (MLST) is a technique in molecular biology for the typing of multiple loci. The procedure characterizes isolates of bacterial species using the DNA sequences of internal fragments of multiple (usually seven) housekeeping genes. and pulsed-field gel electrophoresis gel electrophoresis
Electrophoresis performed in a gel composed of agarose, polyacrylamide, or starch. . Although most European and American isolates were highly diverse, one clonal grouping was identified in sporadic disease and carrier strains isolated over the last 2 decades in the United Kingdom, the Netherlands, Germany, and the United States. In contrast to the diversity in the European and American isolates, most carrier and disease isolates recovered during the last 30 years in countries in the African meningitis belt meningitis belt A popular term for a region of sub-Saharan Africa where epidemics of group A meningococcal infection occur in cycles of
± 10 yrs belonged to a second clonal grouping. During the last decade, these bacteria have caused meningitis outbreaks in Niger and Ghana. These results support the development of a comprehensive conjugate vaccine that would include serogroup X polysaccharide polysaccharide: see carbohydrate.
Any of a large class of long-chain sugars composed of monosaccharides. Because the chains may be unbranched or branched and the monosaccharides may be of one, two, or occasionally more kinds, .
Bacterial meningitis bacterial meningitis Acute bacterial meningitis Neurology Meningeal inflammation caused by bacteria which, if untreated, is often fatal, or associated with significant sequelae Epidemiology 60% are community-acquired–CM, 40% nosocomial–NM Predisposing due to Neisseria meningitidis Neisseria men·in·git·i·dis
The bacteria that is the causative agent of cerebrospinal meningitis; meningococcus.
Neisseria meningitidis (meningococcus meningococcus
Neisseria meningitidis, the bacterium that causes meningococcal meningitis in humans, the only natural hosts in which it causes disease. Meningococci are spherical, frequently occur in pairs, and are strongly gram-negative (see gram stain). ) causes epidemics in Africa usually associated with serogroup A meningococci. Sporadic cases, outbreaks, and hyperendemic disease in Europe and the United States are usually caused by serogroups B and C (1). Occasionally, however, endemic disease Endemic disease
An infectious disease that occurs frequently in a specific geographical locale. The disease often occurs in cycles. Influenza is an example of an endemic disease. and outbreaks are caused by bacteria belonging to other serogroups, including W135, Y, and X. Serogroup X N. meningitidis was described in the 1960s (2,3), and serogroup X meningitis has been observed in North America (4), Europe (5,6), Australia (7), and Africa (8,9). Serogroup X outbreaks have been reported in Niger (10,11) and Ghana (12). In some cases, serogroup X disease has been associated with a deficiency of particular complement components (13,14) or with AIDS (15).
Asymptomatic nasopharyngeal nasopharyngeal
pertaining to the nasal and pharyngeal cavities.
see nasopharyngeal meatus.
see reverse sneeze. carriage of N. meningitidis is common, and in only a small percentage of colonized Colonized
This occurs when a microorganism is found on or in a person without causing a disease.
Mentioned in: Isolation persons do the bacteria invade the bloodstream and cerebrospinal fluid cerebrospinal fluid (CSF)
Clear, colourless liquid that surrounds the brain and spinal cord and fills the spaces in them. It helps support the brain, acts as a lubricant, maintains pressure in the skull, and cushions shocks. to cause disease. Meningococcal populations are highly diverse, and lineages of meningococci with increased capacity to cause invasive disease are thought to arise periodically and spread, sometimes globally (16). Relatively few of these hyperinvasive lineages or clonal groupings are responsible for most meningococcal disease worldwide (17). These clonal groupings diversify during spread (18,19), primarily as a result of frequent horizontal genetic exchange (19-21). However, many variants are isolated only rarely or from a single country and are not transmitted further because of bottlenecks associated with geographic spread and competition (19,22). The population structure of N. meningitidis is effectively panmictic pan·mic·tic
Relating to panmixia. as a result of frequent horizontal genetic exchange (23), but that of some groupings, such as epidemic serogroup A meningococci, is largely clonal (24). The population structure of serogroup X meningococci has not yet been investigated in detail.
After an epidemic of serogroup A disease in 1997-1998 in northern Ghana (9), we conducted a longitudinal carriage study to investigate the dynamics of meningococcal carriage during an interepidemic period (12). We observed a sharp increase in nasopharyngeal carriage of serogroup X meningococci by healthy persons, accompanied by several cases of serogroup X meningitis. To investigate the phylogenetic phy·lo·ge·net·ic
1. Of or relating to phylogeny or phylogenetics.
2. Relating to or based on evolutionary development or history. relationships of these bacteria, we compared the isolates from Ghana with other serogroup X meningococci isolated during recent decades in Africa, Europe, and North America.
Materials and Methods
We analyzed 134 N. meningitidis isolates of serogroup X by pulsed-field gel electrophoresis (PFGE PFGE Pulsed-Field Gel Electrophoresis ) (130 isolates) or multilocus sequence typing (MLST MLST Multi Locus Sequence Typing
MLST Medical Logistics Support Team
MLST Mini Losi Super Truck (1/18th scale radio control vehicle) ) (41 isolates). Of these bacteria, 102 were isolated in Africa from 1970 to 2000: from meningitis patients (9 isolates) and healthy carriers (70 isolates) in Ghana, 1998-2000; from healthy carriers in Mall in 1970 (9 isolates) and 1990-91 (4 isolates); and from patients in Chad (1995, 1 isolate), Niger (1997-1998, 4 isolates), and Burkina Faso (1996-1998, 5 isolates). Six isolates were not tested serologically; the other 96 were NT:P1.5.
In addition, 32 serogroup X strains isolated from 1988 to 2000 in the United Kingdom (22 isolates), Germany (3 isolates), United States (4 isolates), France (1 isolate), Norway (1 isolate), and the Netherlands (1 isolate) were included in the analysis. The 26 strains subjected to further testing had diverse serotypes (2b, 4, 4/21, 14, 16, 21, 22) and serosubtypes (non-subtypable [NST NST nonstress test.
NST Nonstress test, see there ], P1.5, P1.5,10, P1.7, P1.12, P1.14, P1.15, P1.16) in various combinations.
Molecular Typing of Bacteria
PFGE was done by digesting chromosomal DNA DNA: see nucleic acid.
or deoxyribonucleic acid
One of two types of nucleic acid (the other is RNA); a complex organic compound found in all living cells and many viruses. It is the chemical substance of genes. prepared in agarose agarose
more highly purified form of agar with similar uses to agar and widely used in the separation of nucleic acid fragments. blocks with NheI and SpeI as described (22), and MLST by sequencing gene fragments of abcZ, adk, aroE, fumC, gdh, pdhC, and pgm, also as described (16; http://www/ mist.net). The detailed MLST results and sources of isolates have been deposited in a public database (http:// www.mlst.net). Additional MLST data for 31 isolates in 30 sequence types were obtained with permission from http:// www.mlst.net.
A neighbor-joining tree was constructed by using the numbers of MLST allele allele (əlēl`): see genetics.
Any one of two or more alternative forms of a gene that may occur alternatively at a given site on a chromosome. differences with Bionumerics 2.0 (25).
PFGE with two discriminatory rare-cutting enzymes (NheI and SpeI) was used to identify groups of closely related strains in 134 isolates of serogroup X N. meningitidis from countries in Africa, Europe, and North America. All but 3 of 102 isolates from Africa had similar PFGE patterns (Figure 1, clonal grouping X-I X-I Ex-Interest ). In contrast, 19 of 32 isolates from Europe and North America had distinct PFGE patterns (Figure 2) that differed from those of the African isolates. However, among the latter 32 strains, similar PFGE patterns were observed for 13 isolates from the United Kingdom, Germany, the Netherlands, and the United States (Figure 2, clonal grouping X-II).
[FIGURES 1-2 OMITTED]
Forty-one isolates, each representing a distinct PFGE pattern, were analyzed by MLST. For bacteria from which multiple isolates with a similar PFGE pattern had been detected, we tested at least one representative from each year and country of isolation. Together with other data in the MLST WEB site (http://www.mlst.net), 39 distinct sequence types (STs) have been found in 50 serogroup X meningococci. The general structure of a neighbor-joining tree of allelic al·lele
One member of a pair or series of genes that occupy a specific position on a specific chromosome.
[German Allel, short for Allelomorph, allelomorph, from English differences resembles a bush, with little phylogenetic structure (Figure 3). However, isolates with similar PFGE patterns were assigned to closely related STs. All 29 clonal grouping X-I isolates analyzed by MLST were in STs ST181, ST182, or ST751 (Figure 3), which differ by one to three of the seven gene fragments (Table). Similarly, all five clonal grouping X-II isolates were in STs 24 and 750, which differ by one of the seven gene fragments (Table). The three unusual African isolates (strain designations D87, D91, and D93) were in ST188, which is very distinct from STs of clonal grouping X-I (Figure 3). These results show that numerous serogroup X isolates from Africa and nearly half the serogroup X isolates from Europe and North America belong to two clonal groupings, while other serogroup X isolates from Europe or North America are quite diverse.
[FIGURE 3 OMITTED]
n. pl. se·rol·o·gies
1. The science that deals with the properties and reactions of serums, especially blood serum.
African isolates of clonal grouping X-I were NT:P1.5. The 11 North American North American
named after North America.
North American blastomycosis
see North American blastomycosis.
North American cattle tick
see boophilusannulatus. and European isolates of clonal grouping X-II for which serologic data were available were 21:P1.16. Diverse serotype serotype /se·ro·type/ (ser´o-tip) the type of a microorganism determined by its constituent antigens; a taxonomic subdivision based thereon.
v. and serosubtype patterns were found for the other isolates from North America and Europe
The PFGE patterns distinguished two finer groups (Ia and Ib) in clonal grouping X-I, which differ consistently in four NheI and three SpeI fragments (Figure 1). All 14 group Ia strains tested were either ST181 or ST182, which differ at one of the seven gene fragments (Table). All 15 group Ib strains tested were ST751, which differs from ST181 and ST182 at two to three loci loci
[L.] plural of locus.
loci Plural of locus, see there (Table). Group Ia included 10 isolates from Mall (1970-1990), 4 isolates from Niger (1997-1998), and the sole isolate from Chad (1995), as well as one of 79 isolates from Ghana (2000). All five isolates from Burkina Faso (1996-1998) and 78 of 79 isolates from Ghana (1998-2000) were in group Ib.
The general population structure of N. meningitidis is panmictic as a result of the frequent import of alleles from unrelated neisseriae (20,23). Furthermore, several MLST studies have demonstrated that meningococci from healthy carriers are highly diverse (16,26). Phylogenetic trees of different housekeeping genes from N. meningitidis are no more congruent with each other than with random trees (27). Our results for sequence typing of housekeeping genes of serogroup X meningococci also fit this pattern. Phylogenetic analysis of allele differences resulted in a bushlike tree that does not seem to contain any deep phylogenetic information. However, two clonal groupings were found in this otherwise panmictic group of bacteria. The same isolates were assigned to both clonal groupings by two independent methods, MLST and PFGE, indicating that these assignments reflect real genetic relationships and do not depend on the methods used.
Similar concordant genetic relationships were discerned in epidemic serogroup A N. meningitidis by multilocus enzyme electrophoresis (MLEE MLEE Multilocus Enzyme Electrophoresis ), random amplification of polymorphic polymorphic - polymorphism DNA (RAPD RAPD Randomly Amplified Polymorphic DNA
RAPD relative afferent pupillary defect (ophthalmology; aka Marcus-Gunn Pupil) ), and MLST; population genetic analyses confirmed that the population structure of these bacteria is clonal (28). Concordant groupings were also discerned by MLEE and MLST among the so-called hypervirulent serogroup B and C isolates of the ET-5 complex, ET-37 complex, lineage III, and cluster A4 (16). Although their apparent clonality may reflect an epidemic population structure (23), this possibility has been excluded for epidemic serogroup A meningococci (28). Therefore, multiple clonal groupings exist in N. meningitidis, even though the population structure of most of the species is panmictic.
The population structure of subgroup III serogroup A meningococci seems to represent continual, sequential replacement of fit genotypes by related variants during periods of several years to decades (19). In subgroup III, nine genoclouds, each consisting of a frequent genotype plus its rarer, less fit variants, have been identified during 3 decades of pandemic pandemic /pan·dem·ic/ (pan-dem´ik)
1. a widespread epidemic of a disease.
2. widely epidemic.
Epidemic over a wide geographic area.
n. spread. Our PFGE data for clonal grouping I of serogroup X suggest that clonal grouping X-I also has a genocloud structure. Two sets of PFGE variants (group Ia and Ib), which might each represent a genocloud, were detected in different countries (Mali, Chad, and Niger; and Burkina Faso and Ghana, respectively). Additional analyses of polymorphic genes are necessary to clarify the uniformity of these groups and to test the similarity of their population structure compared with that of subgroup III.
Both serogroup X clonal groupings described here were isolated over decades, on multiple occasions, and from diverse locations. Clonal grouping X-I (1970-2000) was isolated from different countries in West Africa, and clonal grouping X-II (1986-1999) was isolated from Europe and North America. For clonal grouping X-I in Ghana, the disease rate in healthy carriers was estimated to be 3/10,000 (12). Clonal grouping X-1 is thus of considerably lower virulence than serogroup B ET5 complex bacteria (disease/carrier rate of 2,100/10,000 ) or serogroup A subgroup III bacteria during a postepidemic period in a vaccinated population (100/10,000 ).
The relationship between bacterial fitness and clonality has not yet been investigated extensively in natural isolates. Variation in virulence between bacterial genotypes leads to more uniformity in disease isolates than in carriage organism in Streptococcus pneumoniae Streptococcus pneu·mo·ni·ae
Streptococcus pneumoniae Microbiology A pathogenic streptococcus with 90 serotypes associated with pneumonia, bacteremia, meningitis Transmission Person to person Incidence (30) and Staphylococcus aureus Staphylococcus au·re·us
A bacterium that causes furunculosis, pyemia, osteomyelitis, suppuration of wounds, and food poisoning.
Staphylococcus aureus Staphylococcus pyogenes (31). However, our data suggest that the clonal structure of certain meningococcal genotypes need not reflect virulence but rather is associated with genotypes that are particularly fit at colonizing the nasopharynx nasopharynx /na·so·phar·ynx/ (-far´inks) the part of the pharynx above the soft palate.nasopharyn´geal
n. and spreading from person to person.
Although clonal grouping X-I bacteria are less virulent than serogroup A and B meningococci, they are still pathogenic. Most strains described here were isolated from asymptomatic carriers or patients with rare endemic cases. However, group Ia caused a meningitis outbreak with >60 cases in 1997 in Niger (11). Group Ib caused a smaller outbreak in 2000 in Ghana (12). These results suggest that X-I meningococci may even be capable of causing epidemics. Meningococci are naturally transformable, and horizontal DNA transfer is frequent in these bacteria (20-22). Meningococcal carriage is usually low in interepidemic periods in Africa (1,12,32,33), offering less opportunity for horizontal genetic exchange, which could account for the low genetic variability in serogroup X meningococci in Africa.
For more than a decade, many countries in the African meningitis belt have vaccinated extensively with A/C polysaccharide vaccines (34). Recently, mass vaccination with conjugated conjugated
estrogens, conjugated Warning - Hazardous drug!
C.E.S. serogroup C vaccines has been implemented in the United Kingdom, and strong initial protection has been reported (35). However, if effective, these vaccines may well select for the spread of bacteria for which they are not protective (36), including unusual causes of disease such as serogroups Y, W135, and X. Capsule switching due to DNA transformation has been documented (37,38), and effective vaccination against serogroups A and C may select for capsule switch variants of fit genotypes expressing a capsular cap·su·lar
Of, relating to, or resembling a capsule.
Adj. 1. capsular - resembling a capsule; "the capsular ligament is a sac surrounding the articular cavity of a freely movable joint and attached to the bones" polysaccharide not included in the vaccination program. The recent outbreaks after the 2000 Hajj hajj (häj), the pilgrimage to Mecca, Saudi Arabia, one of the five basic requirements (arkan or "pillars") of Islam. Its annual observance corresponds to the major holy day id al-adha, pilgrimage, caused by W 135 ET-37 complex meningococci (39,40), may reflect exactly such selection. These findings support the development of comprehensive conjugate vaccines that include capsular polysaccharides from formerly rare causes of disease such as serogroup X.
Table. Multilocus sequence typing results of two serogroup X Neisseria meningitidis clonal groupings Allele numbers ST AbcZ Adk aroE FumC gdh pdhC Pgm 24 2 5 2 7 15 20 5 750 2 5 2 9 15 20 5 181 10 3 15 7 5 41 31 182 10 3 15 26 5 41 31 751 10 3 15 7 8 41 6 ST Country (no. of isolates) Yr 24 Netherlands (1), United States (1) 1986, 1993 750 United Kingdom (2), Germany (1) 1998-1999 181 Mali (6), Chad (1), Niger (2), Ghana (1) 1970-2000 182 Mali (4) 1970 751 Burkina Faso (3), Ghana (12) 1996-2000
We gratefully acknowledge the helpful comments and support of Alex Nazzar and Daniel Falush and the receipt of isolates from Dominique Caugant, Tanja Popovic, Ed Kaczmarski, and Mohamed-Kheir Taha.
This work was funded by the Stanley Thomas Johnson Foundation. Part of the work (P.K.) was supported by the research grant NI/ 6882-3 of the Internal Grant Agency of the Ministry of Health of the Czech Republic.
This publication made use of the Neisseria MultiLocus Sequence Typing website (http://neisseria.mlst.net) developed by Man-Suen Chan, funded by the Wellcome Trust, and located at the University of Oxford. We thank Keith Jolly for allowing the use of deposited data. Technical assistance by Santama Abdulai, Titus Tei, Susanne Faber, Marion Moebes, and Barica Kusecek is greatly appreciated.
Dr. Gagneux is a postdoctoral research fellow at the Swiss Tropical Institute The Swiss Tropical Institute (STI, also known as Institut Tropical Suisse and Schweizerisches Tropeninstitut) is an Associated Institute of the University of Basel. It was founded in 1943 by Professor Rudolf Geigy as a public organization, with support from the Swiss Federal . His research interests focus on the epidemiologic and genetic characterization of Neisseria meningitidis and Mycobacterium tuberculosis Mycobacterium tuberculosis
Mycobacterium tuberculosis .
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Arising or occurring between species.
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Arising or occurring between species.
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Address for correspondence: Gerd Pluschke, Swiss Tropical Institute, Socinstrasse 57, 4002 Basel, Switzerland; fax: +41 61-271 8654; e-mail: email@example.com
Sebastien Gagneux, * ([dagger]) Thierry Wirth, ([double dagger]) Abraham Hodgson, ([dagger]) Ingrid Ehrhard, ([section]) Giovanna Morelli, ([double dagger]) Paula Kriz, ([paragraph]) Blaise Genton, * Tom Smith,* Fred Binka, ([dagger]) Gerd Pluschke, * and Mark Achtman ([dagger])
* Swiss Tropical Institute, Basel, Switzerland; ([dagger]) Navrongo Health Research Centre, Ministry of Health, Navrongo, Ghana; ([double dagger]) Max-Planck-Institut fur Infektionsbiologie, Berlin, Germany; ([section]) University of Heidelberg, Heidelberg, Germany; and ([paragraph]) National Institute of Public Health, Prague, Czech Republic