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Genetic characterisation of Meningococci
Linköping University, Department of Molecular and Clinical Medicine, Clinical Microbiology. Linköping University, Faculty of Health Sciences.
2001 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Meningococci (Mc) are one of the major causes of meningitis and septicaemia throughout the world. Non-culture diagnostic methods are recognised as important tools for optimal laboratory confirmation of Me infections, due in part to the increased use of preadmission antibiotics. Non-culture methods were designed in England to detect group B, C, Y and W-135 Mc. To add to the repertoire of genetic methods used for grouping, conventional PCR able to identify Me group A DNA from the cerebrospinal fluid was developed (I). This means that most invasive Me can now be detected and directly grouped even in culture-negative samples. The PCR concept was adapted to the direct and rapid LightCycler PCR, which made it possible to detect and characterise Me (A, B, C, Y, W-135 and porA) within a few hours (II). This can be compared to conventional PCR, including gel electrophoresis, which takes at least a full working day. Genetic characterisation, like genosubtyping of Me, is more widely used because of the increased number of samples that are non-serosubtypable by serological methods. Genosubtyping based on three variable regions within the porA gene gives a complete subtype characterisation, which is important for epidemiological purposes as well as for the design of certain vaccines (III-V). The genosubtyping method is suitable as a first step in an epidemiological investigation, while pulsed-field gel electrophoresis is useful for further investigation of similarity between strains in local outbreaks or strains that are suspected to be epidemiologically related (IV & V).

Antibiotic resistance is more frequent these days and is often correlated to genes located in the chromosome or in a plasmid. ß-lactamase producing Me is not common. However, a few Me harbouring plasmids with a ß-lactamase gene have been isolated in the world. The first full sequence of such a plasmid was published in paper VI. It was shown to be a possible variant of a gonococcal plasmid, pJD5, and may therefore have been picked up from that species. It is of great importance to observe the spread of these Me that harbour plasmids like pAB6, since increased spread may require changes in antibiotic treatment strategies.

Abstract [sv]

Meningokockmeningit och/eller sepsis är infektion på hjärnhinnan (hjärnhinneinflammation) och/eller i blodet orsakad av Neisseria meningitidis bakterier, även kallade meningekocker (Mc). Sjukdomen kan framkalla stor rädsla hos många föräldrar, familjemedlemmar och av vårdpersonal eftersom den ofta utvecklas snabbt, har en hög dödlighet och kan vara svår att skilja från andra febersjukdomar. De som överlever kan ha fått permanenta vävnadsskador och neurologiska problem. Den snabba utvecklingen av sjukdomen hos vanligen friska barn eller ungdomar har resulterat i intensiv forskning inom området. Speciellt gäller det diagnostik och karakteriseringsmetoder, vaccinutveckling, samt vad det är som gör vissa sorter av Mc mer virulenta (sjukdomsframkallande) än andra. Denna avhandling (Papper I-VI) handlar om utvecklingen av genetiska metoder för att både mer fullständigt och snabbare kunna identifiera och karakterisera Mc.

Mc sjukdom diagnostiseras vanligen genom att man odlar fram bakterien, men p.g.a. av det ökande användandet av antibiotika och ev. transportproblem kan många prov bli falskt "negativa". För att identifiera de mest sjukdomsframkallande grupperna (A, B, C, Y och W-135) har genetiska metoder nu utvecklats/vidareutvecklats (Papper I, II). Bakterien delas även in i subtyper, vilka också inverkar på bakteriens virulens. Vanligen görs denna karakterisering från odlade bakterier men man har mer och mer övergått till att utgå från bakteriens DNA (genosubtypning) för att få en fullständig karakterisering (Papper III-V). För epidemiologiska syften kan genesubtypning användas tillsammans med en metod där bakteriens DNA delas upp i småbitar för att få ett s.k. "fingeravtryck" av bakterien (Papper IV-V).

I papper VI presenteras den första DNA sekvensen på en ovanligt förekommande Mc plasmid, innehållande genen för ß-laktamas, vilket gör det möjligt för bakterien att byta ner penicillin-antibiotika och gör den därmed resistent. Plasmiden visade sig vara en variant av en plasmid man hittat hos gonokocker (Ge), en nära släkting till Mc, vilket gör det troligt att plasmiden har överförts från Ge. Blir dessa plasmider vanligare hos Mc skulle en förändring av nuvarande antibiotikabehandling av Mc sjukdom behöva göras.

Place, publisher, year, edition, pages
Linköping: Linköping University Electronic Press, 2001. , 79 p.
Series
Linköping University Medical Dissertations, ISSN 0345-0082 ; 697
National Category
Medical and Health Sciences
Identifiers
URN: urn:nbn:se:liu:diva-28613Local ID: 13768ISBN: 91-7373-135-8 (print)OAI: oai:DiVA.org:liu-28613DiVA: diva2:249424
Public defence
2001-11-16, Wilandersalen, Universitetssjukhuset, Linköping, 10:00 (Swedish)
Opponent
Available from: 2009-10-09 Created: 2009-10-09 Last updated: 2012-08-20Bibliographically approved
List of papers
1. PCR Identification of the Group A Neisseria Meningitidis Gene in Cerebrospinal Fluid
Open this publication in new window or tab >>PCR Identification of the Group A Neisseria Meningitidis Gene in Cerebrospinal Fluid
1999 (English)In: Scandinavian Journal of Infectious Diseases, ISSN 0036-5548, E-ISSN 1651-1980, Vol. 31, no 5, 481-483 p.Article in journal (Refereed) Published
Abstract [en]

The aim of this study was to develop a PCR method for direct identification of Neisseria meningitidis serogroup A in cerebrospinal fluid. The assay makes use of unique sites within the gene cassette responsible for expression of the (α1→6)-linked N-acetyl-D-mannosamine-1-phosphate serogroup A capsule. A total of 67 different N. meningitidis strains and 12 clinical samples of CSF, culture positive for N. meningitidis, were examined. All the strains and samples of N. meningitidis serogroup A were correctly identified by an amplified PCR product of 519 bp. The PCR method for identification is specific for the group A gene of N. meningitidis. The assay may contribute to reducing recurrent, devastating epidemics of meningococcal infection by providing a diagnostic tool for grouping in developing countries where problems with false negative cultures are common and vaccination against serogroup A meningococci may be required.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-26071 (URN)10.1080/00365549950164003 (DOI)10530 (Local ID)10530 (Archive number)10530 (OAI)
Available from: 2009-10-08 Created: 2009-10-08 Last updated: 2017-12-13Bibliographically approved
2. Direct and Rapid Identification and Genogrouping of Meningococci and porA Amplification by LightCycler PCR
Open this publication in new window or tab >>Direct and Rapid Identification and Genogrouping of Meningococci and porA Amplification by LightCycler PCR
2002 (English)In: Journal of Clinical Microbiology, ISSN 0095-1137, E-ISSN 1098-660X, Vol. 40, no 12, 4531-4535 p.Article in journal (Refereed) Published
Abstract [en]

Invasive meningococcal infections are usually diagnosed by culture. This approach is far from optimal due to, e.g., treatment with precollection antibiotics. Molecular-genetics methods are therefore recognized as important tools for optimal laboratory confirmation of meningococcal infections as well as characterization of meningococci (Mc). The aims of the present study were to develop real-time PCRs for identification and genogrouping (A, B, C, Y, and W-135) of Mc and porA amplification that further can be used for subsequent genosubtyping. In a first run Mc were identified. In a second run they were genogrouped and porA genes were amplified. All the Mc isolates (n = 71) but one and cerebrospinal fluid samples (n = 11) tested gave the expected positive results. The specificity, inter- and intra-assay variations, and effects of different amounts of DNA on the melting temperatures were also explored. The LightCycler PCR system was found to effectively detect and characterize Mc in a few hours. This testing, including the DNA sequencing of the porA gene to reveal the genosubtype, does not take more than a working day, and the results can be compared to those from culturing with phenotypic analysis, which takes at least a few days.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-26553 (URN)10.1128/​JCM.40.12.4531-4535.2002 (DOI)11115 (Local ID)11115 (Archive number)11115 (OAI)
Note
On the day of the defence day the status of this article was a manuscript.Available from: 2009-10-08 Created: 2009-10-08 Last updated: 2017-12-13Bibliographically approved
3. Genosubtyping by sequencing group A, B and C meningococci: a tool for epidemiological studies of epidemics, clusters and sporadic cases
Open this publication in new window or tab >>Genosubtyping by sequencing group A, B and C meningococci: a tool for epidemiological studies of epidemics, clusters and sporadic cases
2000 (English)In: Acta Pathologica, Microbiologica et Immunologica Scandinavica (APMIS), ISSN 0903-4641, E-ISSN 1600-0463, Vol. 108, no 7-8, 509-516 p.Article in journal (Refereed) Published
Abstract [en]

Genosubtyping, by sequencing variable regions (VRs) 1, 2 and 3 of the porA gene, was evaluated as a tool to detect clonality of isolates in meningococcal epidemics in Africa and clusters of disease in Sweden. All 63 examined meningococcal isolates were successfully genosubtyped. The isolates belonging to group A type 4 with genosubtype P1.20,9,35a showed little heterogeneity in African epidemics in 1988 and onwards. In Sweden, two meningococcal clones of group B type 15, with genosubtypes P1.7,16,35 and P1.7,16f,35, dominated during two clusters of meningococcal disease in 1995–96 and in sporadic cases thereafter. The characterisation of group C meningococci isolated during 1992 in Sweden indicated a cluster (type 2a with genosubtype P1.5a,10d,36b) connected with a discotheque visit. Two variants of VR2 (10p and 25b), not previously described, were found among the examined isolates. Nucleotide sequence analysis of VRs in the porA gene proved a valuable epidemiological tool since almost all isolates could be genosubtyped, in contrast to the phenotypic methods presently used.

Keyword
Epidemiology, genosubtyping, sequencing, Neisseria meningitidis, meningococcal disease
National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-25867 (URN)10.1034/j.1600-0463.2000.01087-8509.x (DOI)10304 (Local ID)10304 (Archive number)10304 (OAI)
Available from: 2009-10-08 Created: 2009-10-08 Last updated: 2017-12-13Bibliographically approved
4. Comparison of Serogroup W-135 Meningococci Isolated in Sweden during a 23-Year Period and Those Associated with a Recent Hajj Pilgrimag
Open this publication in new window or tab >>Comparison of Serogroup W-135 Meningococci Isolated in Sweden during a 23-Year Period and Those Associated with a Recent Hajj Pilgrimag
2001 (English)In: Journal of Clinical Microbiology, ISSN 0095-1137, E-ISSN 1098-660X, Vol. 39, no 7, 2695-2699 p.Article in journal (Refereed) Published
Abstract [en]

An outbreak of serogroup W-135 meningococcal disease was reported among pilgrims returning from the annual hajj (pilgrimage to Mecca) in mid-March 2000. Molecular characterization was used to investigate the similarity of the hajj-associated W-135 strains with those isolated in Sweden during a 23-year period (1978 to 2000). The same hajj-associated genosubtype, genosubtype P1.5,2,36b, has been documented in Sweden since 1979, while pulsed-field gel electrophoresis and the sulfadiazine resistance of the W-135 isolates indicated that the outbreak was probably due to a new clone of W-135 meningococci.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-25865 (URN)10.1128/JCM.39.7.2695-2699.2001 (DOI)10302 (Local ID)10302 (Archive number)10302 (OAI)
Available from: 2009-10-08 Created: 2009-10-08 Last updated: 2017-12-13Bibliographically approved
5. Long-Term Persistence of a Discotheque-Associated Invasive Neisseria meningitidis Group C Strain as Proven by Pulsed-Field Gel Electrophoresis and porA Gene Sequencin
Open this publication in new window or tab >>Long-Term Persistence of a Discotheque-Associated Invasive Neisseria meningitidis Group C Strain as Proven by Pulsed-Field Gel Electrophoresis and porA Gene Sequencin
2000 (English)In: Journal of Clinical Microbiology, ISSN 0095-1137, E-ISSN 1098-660X, Vol. 38, no 4, 1638-1640 p.Article in journal (Refereed) Published
Abstract [en]

A cluster of a Neisseria meningitidis serogroup C strain causing invasive disease was investigated. Five out of seven cases were associated with a particular discotheque. The strains were indistinguishable, as revealed by pulsed-field gel electrophoresis and sequencing of variable regions of the porA gene, but caused strikingly different clinical presentations during 5 months.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-25919 (URN)10361 (Local ID)10361 (Archive number)10361 (OAI)
Available from: 2009-10-08 Created: 2009-10-08 Last updated: 2017-12-13Bibliographically approved
6. Complete Sequence of a β-Lactamase-Encoding Plasmid in Neisseria meningitidis
Open this publication in new window or tab >>Complete Sequence of a β-Lactamase-Encoding Plasmid in Neisseria meningitidis
Show others...
2000 (English)In: Antimicrobial Agents and Chemotherapy, ISSN 0066-4804, E-ISSN 1098-6596, Vol. 44, no 1, 210-212 p.Article in journal (Refereed) Published
Abstract [en]

Identical β-lactamase-encoding (TEM-1) plasmids were found in two different clinical Neisseria meningitidis strains. They were completely sequenced (5,597 bp) and designated pAB6. The plasmid is almost identical to Neisseria gonorrhoeae plasmid pJD5 (5,599 kb) and may have been picked up from a gonococcus in vivo.

National Category
Medical and Health Sciences
Identifiers
urn:nbn:se:liu:diva-25866 (URN)10.1128/​AAC.44.1.210-212.2000 (DOI)10303 (Local ID)10303 (Archive number)10303 (OAI)
Available from: 2009-10-08 Created: 2009-10-08 Last updated: 2017-12-13Bibliographically approved

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