| 1. |
- Hedberg, Sara Thulin, et al.
(författare)
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Antibiotic susceptibility and characteristics of Neisseria meningitidis isolates from the African meningitis belt, 2000 to 2006 : phenotypic and genotypic perspectives
- 2009
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Ingår i: Antimicrobial Agents and Chemotherapy. - 0066-4804 .- 1098-6596. ; 53:4, s. 1561-1566
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Tidskriftsartikel (refereegranskat)abstract
- Up-to-date information regarding the antibiotic susceptibility of Neisseria meningitidis strains from African countries is highly limited. Our aim was to comprehensively describe the antibiotic susceptibilities of a selection of N. meningitidis isolates recovered between 2000 and 2006 from 18 African countries, mainly those within the meningitis belt. Susceptibilities to 11 antibiotics were determined using Etest for 137 N. meningitidis isolates (stringently selected from 693 available isolates). The isolates were also characterized by serogrouping, multilocus sequence typing, genosubtyping, and penA allele identification. All N. meningitidis isolates were susceptible to ceftriaxone, chloramphenicol, and ciprofloxacin. No isolate produced beta-lactamase. Only three isolates (2%) displayed reduced susceptibility to penicillin G. The two isolates with the highest penicillin G MICs were the only isolates showing reduced susceptibility to ampicillin and cefuroxime. One of these isolates was also resistant to penicillin V. One percent of isolates displayed reduced susceptibility to rifampin, while 52% of the isolates were resistant to tetracycline, 74% were resistant to erythromycin, and 94% were resistant to sulfadiazine. The MICs of rifampin and tetracycline seemed to be associated with the serogroup of the isolates. In total, 18 sequence types (STs), 10 genosubtypes, and 8 different penA alleles were identified; the most common were ST-7, P1.20,9,35-1, and penA4, respectively. A high level of correlation was found between ST, genosubtype, and penA allele. In conclusion, N. meningitidis isolates from the African meningitis belt remain highly susceptible to the antibiotics used. Regarding beta-lactam antibiotics, rare isolates showed a reduced susceptibility to penicillins, but the expanded-spectrum cephalosporins are not affected at present.
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| 2. |
- Hedberg, Sara Thulin, et al.
(författare)
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Combined real-time PCR and pyrosequencing strategy for objective, sensitive, specific, and high throughput identification of reduced susceptibility to penicillins in Neisseria meningitidis
- 2008
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Ingår i: Antimicrobial Agents and Chemotherapy. - Washington, DC : American Society for Microbiology. - 0066-4804 .- 1098-6596. ; 52:2, s. 753-756
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Tidskriftsartikel (refereegranskat)abstract
- A segment of penA in Neisseria meningitidis strains (n = 127), including two nucleotide sites closely associated to reduced susceptibility to penicillins, was amplified and pyrosequenced. All results were in concordance with Sanger sequencing, and a high correlation between alterations in the two Pen(i)-specific sites and reduced susceptibility to penicillins was identified.
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| 3. |
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| 4. |
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| 5. |
- Jacobsson, Susanne, 1974-, et al.
(författare)
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Prevalence and sequence variations of the genes encoding the five antigens included in the novel 5CVMB vaccine covering group B meningococcal disease
- 2009
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Ingår i: Vaccine. - Amsterdam : Elsevier. - 0264-410X .- 1873-2518. ; 27:10, s. 1579-1584
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Tidskriftsartikel (refereegranskat)abstract
- During the recent years, projects are in progress for designing broad-range non-capsular-based meningococcal vaccines, covering also serogroup B isolates. We have examined three genes encoding antigens (NadA, GNA1030 and GNA2091) included in a novel vaccine, i.e. the 5 Component Vaccine against Meningococcus B (5CVMB), in terms of gene prevalence and sequence variations. These data were combined with the results from a similar study, examining the two additional antigens included in the 5CVMB (fHbp and GNA2132).nadA and fHbp v. 1 were present in 38% (n=36), respectively 71% (n=67) of the isolates, whereas gna2132, gna1030 and gna2091 were present in all the Neisseria meningitidis isolates tested (n=95). The level of amino acid conservation was relatively high in GNA1030 (93%), GNA2091 (92%), and within the main variants of NadA and fHbp. GNA2132 (54% of the amino acids conserved) appeared to be the most diversified antigen. Consequently, the theoretical coverage of the 5CVMB antigens and the feasibility to use these in a broad-range meningococcal vaccine is appealing.
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| 6. |
- Lindh, Ingrid, et al.
(författare)
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Feeding of mice with Arabidopsis thaliana expressing the HIV-1 subtype C p24 antigen gives rise to systemic immune responses
- 2008
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Ingår i: Acta Pathologica, Microbiologica et Immunologica Scandinavica (APMIS). - Oxford : Blackwell. - 0903-4641 .- 1600-0463 .- 0903-465X .- 1600-5503. ; 116:11, s. 985-994
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Tidskriftsartikel (refereegranskat)abstract
- Development of transgenic edible plants, to be used as production, storage and delivery systems for recombinant vaccine antigens, is a promising strategy to obtain cost effective vaccines against infectious diseases, not the least for use in developing countries. Therefore, we used Agrobacterium tumefaciens-mediated gene transfer to introduce the p24 gag gene encoding the nucleocapsid protein from HIV-1 subtype C into the Arabidopsis thaliana plant genome. Eighteen plant lines were confirmed positive for the p24 gene by PCR, four of these lines showed an apparent homozygous phenotype when grown on selective medium and these lines also showed transcription of the p24 gene into its corresponding mRNA. The mRNA in all four cases generated the p24 protein in plants, as verified by western blot analysis. The plants were shown to contain between 0.2 µg and 0.5 µg p24 protein per g of fresh tissue. Analysis of the localisation of the p24 protein showed that stem tissue contained the largest amount of protein, more than twice as much as leaf tissue, whereas no p24 protein was detected in roots. By using Southern blotting, we found that 4, 2-3, 2 and 1 T-DNA insertion events took place in the four lines 1, 2, 7, and 10, respectively. The genetic insertions of line 1 were stable from the T1 to the T4 generation and gave rise to the p24 protein in all cases, as verified by western blotting. In mice fed with fresh transgenic A. thaliana (line 10), anti-gag IgG was obtained in serum after a booster injection with recombinant p37Gag. No immune response was observed after equal booster injection of untreated mice or mice fed with A. thaliana WT plants.
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| 7. |
- Taha, Muhamed-Kheir, et al.
(författare)
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Defining the breakpoint for resistance to rifampicin in Neisseria meningitidis by rpoB sequencing
- 2009
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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| 8. |
- Thulin Hedberg, Sara
(författare)
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Antibiotic susceptibility and resistance in Neisseria meningitidis : phenotypic and genotypic characteristics
- 2009
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- 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.
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