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Increased genetic diversity of Neisseria meningitidis isolates after the introduction of meningococcal serogroup C polysaccharide conjugate vaccines
No full textDuring the 1990s, the incidence of meningococcal disease was high in the United Kingdom. This was due primarily to an increase in serogroup C disease, particularly that within the ET-37/ST-11 genetic lineage. Serogroup C meningococcal polysaccharide conjugate vaccines were introduced in the United Kingdom in 1999, but the sequence types of meningococci causing disease since that time have not yet been reported. We have used serogrouping and multilocus sequence typing to characterize meningococci from patients with invasive disease over a 4-year period and show that there is a significant increase in genetic diversity but no genetic evidence of capsule switching.</p
Molecular methods for the detection and characterization of Neisseria meningitidis
No full textNeisseria meningitidis remains a common global cause of morbidity and mortality. The laboratory confirmation of meningococcal disease is, therefore, very important for individual patient management and for public health management. Through surveillance schemes, it provides long-term epidemiologic data that can be used to inform vaccine policy. Traditional methods, such as latex agglutination and the enzyme-linked immunosorbent assay, are still used, but molecular methods are now also established. In this review, molecular methods for the laboratory confirmation and characterization of meningococci are described. PCR is an invaluable tool in modern biology and can be used to predict the group, type and subtype of meningococci. It is now also used in a fluorescence-based format for increased sensitivity and specificity. The method also provides the amplified DNA for other techniques, such as multilocus sequence typing. Other methods for the discrimination of meningococci have also played and continue to play an important part in epidemiology. For example, pulsed-field gel electrophoresis is highly discriminatory, whilst multilocus enzyme electrophoresis provided the basis for the description of global meningococcal clones and formed the foundation for multilocus sequence typing. Other less commonly used methods, such as matrix-assisted laser desorption/ionization time-of-flight mass spectrometry and pyrosequencing, may increasingly find their way into microbiology reference laboratories. Nevertheless, nucleotide sequencing and laboratory automation have aided the introduction of many methods and provide data that are digitally based and, therefore, highly accurate and portabl
Nucleotide sequence-based typing of meningococci directly from clinical samples
No full textThe unpredictable characteristics of meningococcal disease (MD) make outbreaks complicated to monitor and consequently lead to high levels of public anxiety. Traditional molecular techniques have been utilized in order to understand better the epidemiology of MD, but some have disadvantages such as being highly specialized and labour-intensive, with low reproducibility. Some of these problems have been overcome by using multilocus sequence typing (MLST). This technique exploits the unambiguous nature and electronic portability of nucleotide sequencing data for the characterization of micro-organisms. The need for enhanced surveillance of MD after the introduction of serogroup C conjugate vaccines means that it is important to gain typing information from the infecting organism in the absence of a culture isolate. Here, the application of MLST for the laboratory confirmation and characterization of Neisseria meningitidis directly from clinical samples is described. This involved using a newly designed set of primers that were complementary to nucleotide sequences external to the existing MLST primers already in use for culture-based MLST of meningococci. This combination has produced a highly sensitive procedure to allow the efficient genotypic characterization of meningococci directly from clinical samples.</p
Automation of a fluorescence-based multiplex PCR for the laboratory confirmation of common bacterial pathogens
No full textA fluorescence-based multiplex PCR was automated for the simultaneous detection of Neisseria meningitidis, Streptococcus pneumoniae and Haemophilus influenzae in clinical samples from patients with suspected meningitis. Sensitivity of one to two genome copies per 100 microl sample and specificity of 100% for each organism were shown. Automation of DNA extraction, liquid handling, PCR and analysis are achieved on a single platform, which enables a high throughput and rapid turnaround of clinical samples that, in turn, leads to faster diagnosis. This is ultimately beneficial to the treatment of the patient and for public health management.</p
Automated pneumococcal MLST using liquid-handling robotics and a capillary DNA sequencer
No full textMultilocus sequence typing (MLST) is used by the Scottish Meningococcus and Pneumococcus Reference Laboratory (SMPRL) as a routine method for the characterization of certain bacterial pathogens. The SMPRL recently started performing MLST on strains of Streptococcus pneumoniae, and here we describe a fully automated method for MLST using a 96-well-format liquid-handling robot and a 96-capillary automated DNA sequencer
Neisseria meningitidis sequence type and risk for death, Iceland
No full textInvasive meningococcal infections are hyperendemic in Iceland, a relatively isolated country in the mid-Atlantic. We performed a nationwide study on all viable meningococcal strains (N = 362) from 1977 to 2004. We analyzed the association of patient's age and sex, meningococcal serogroups, and sequence types (STs) with outcomes. Overall, 59 different STs were identified, 19 of which were unique to Iceland. The most common STs were 32 (24.6%), 11 (19.9%), and 10 (10.2%). The unique ST-3492 ranked fourth (7.7%). The most common serogroups were B (56.4%), C (39.8%), and A (2.2%). Age (p < 0.001) and infection with a unique ST (p = 0.011) were independently associated with increased death rates, whereas isolation of meningococci from cerebrospinal fluid only was associated with lower death rates (p = 0.046). This study shows evolutionary trends of meningococcal isolates in a relatively isolated community and highlights an association between unique STs and poor outcome
The molecular characterisation of Neisseria meningitidis in Scotland before, during and after the initial introduction of the meningococcal serogroup C conjugate (MenC) vaccines
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
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