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Defining the breakpoint for resistance to rifampicin in Neisseria meningitidis by rpoB sequencing
Örebro University, School of Health and Medical Sciences.
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2009 (English)Manuscript (preprint) (Other academic)
Abstract [en]

Clinical isolates of Neisseria meningitidis resistant to rifampicin are important to identify asthey lead to failure of chemoprophylaxis of meningococcal disease. However, theidentification of these isolates is hindered by the absence of a harmonized breakpoint despiteefforts of standardization. In the present study, a large number (n=352) of clinical N.meningitidis isolates from 12 mainly European countries and spanning over 25 years (1984 to2009) were examined. The collection comprised all clinical isolates with MIC 0.25 mg/lreceived by the national reference laboratories for meningococci in the participating countries(n=161). In addition, representative isolates displaying MIC of rifampicin <0.25 mg/l wereexamined (n=191). Phenotyping and genotyping of isolates were performed and a 660 bpDNA fragment of the rpoB gene was sequenced in all the included isolates. Sequencesdiffering by at least one nucleotide were defined as a unique rpoB allele (n=55). Geometricmeans of MIC were calculated for isolates displaying the same allele. All the clinical isolatesdisplaying MIC >1 mg/l of rifampicin possessed rpoB alleles with critical mutations (in total21 alleles), resulting in substitutions at the codon H552 and less frequently at nearby codons(S548 and S557). These alterations were absent in the alleles (n=34) found in all isolates withMIC 1 mg/l. Based on these findings, rifampicin susceptible isolates could be defined asthose with MIC 1 mg/l. A new web site was created based on the data from this work (http://neisseria.org/nm/typing/rpoB). The rifampicin resistant isolates belonged to diversegenetic lineages and provoked lower bacteremia levels in mice. This biological cost mayexplain the non-expansion of the rifampicin resistant isolates.

Place, publisher, year, edition, pages
2009.
National Category
Medical and Health Sciences
Research subject
Medicine
Identifiers
URN: urn:nbn:se:oru:diva-8655OAI: oai:DiVA.org:oru-8655DiVA: diva2:278354
Available from: 2009-11-25 Created: 2009-11-25 Last updated: 2011-05-02Bibliographically approved
In thesis
1. Antibiotic susceptibility and resistance in Neisseria meningitidis: phenotypic and genotypic characteristics
Open this publication in new window or tab >>Antibiotic susceptibility and resistance in Neisseria meningitidis: phenotypic and genotypic characteristics
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Neisseria meningitidis, also known as the meningococcus, is a globally spread obligate human bacterium causing meningitis and/or septicaemia. It is responsible for epidemics in both developed and developing countries. Untreated invasive meningococcal disease is often fatal, and despite modern intensive care units, the mortality is still remarkably high (approximately 10%). The continuously increasing antibiotic resistance in many bacterial pathogens is a serious public health threat worldwide and there have been numerous reports of emerging resistance in meningococci during the past decades.

In paper I, the gene linked to reduced susceptibility to penicillins, the penA gene, was examined. The totally reported variation in all published penA genes was described. The penA gene was highly variable (in total 130 variants were identified). By examination of clinical meningococcal isolates, the association between penA gene sequences and penicillin susceptibility could be determined. Isolates with reduced susceptibility displayed mosaic structures in the penA gene. Two closely positioned nucleotide polymorphisms were identified in all isolates with reduced penicillin susceptibility and mosaic structured penA genes. These alterations were absent in all susceptible isolates and were successfully used to detect reduced penicillin susceptibility by real-time PCR and pyrosequencing in paper II. In papers III and IV, antibiotic susceptibility and characteristics of Swedish and African meningitis belt meningococcal isolates were comprehensively described. Although both populations were mainly susceptible to the antibiotics used for treatment and prophylaxis, the proportion of meningococci with reduced penicillin susceptibility was slightly higher in Sweden. A large proportion of the African isolates was resistant to tetracycline and erythromycin. In paper V, the gene linked to rifampicin resistance, the rpoB gene, was examined in meningococci from 12 mainly European countries. Alterations of three amino acids in the RpoB protein were found to always and directly lead to rifampicin resistance. A new breakpoint for rifampicin resistance in meningococci was suggested. The biological cost of the RpoB alterations was investigated in mice. The pathogenicity/virulence was significantly lower in rifampicin resistant mutants as compared with susceptible wild-type bacteria.

Place, publisher, year, edition, pages
Örebro: Örebro universitet, 2009. 94 p.
Series
Örebro Studies in Medicine, ISSN 1652-4063 ; 38
Keyword
Neisseria meningitidis, meningococcal disease, antibiotic resistance, antibiotic susceptbility, biological cost, PCR, sequencing
National Category
Cell and Molecular Biology Microbiology in the medical area Microbiology in the medical area Microbiology in the medical area
Research subject
Biomedicine; Medicine
Identifiers
urn:nbn:se:oru:diva-8652 (URN)978-91-7668-702-4 (ISBN)
Public defence
2009-12-18, Wilandersalen, Universitetssjukhuset Örebro, Örebro, 09:00 (English)
Opponent
Supervisors
Available from: 2009-11-25 Created: 2009-11-25 Last updated: 2011-05-02Bibliographically approved

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