5' exonuclease assay for detection of serogroup Y Neisseria meningitidis

Comparison of Phenotypic and Genotypic Approaches to Capsule Typing of Neisseria meningitidis by Use of Invasive and Carriage Isolate Collections

Neisseria meningitidis serogroup B (MnB) is a leading cause of bacterial meningitis; however, MnB is most commonly associated with asymptomatic carriage in the nasopharyngeal cavity, as opposed to the disease state. Two vaccines are now licensed for the prevention of MnB disease; a possible additional benefit of these vaccines could be to protect against disease indirectly by disrupting nasopharyngeal carriage (e.g., herd protection). To investigate this possibility, accurate diagnostic approaches to characterize MnB carriage isolates are required. In contrast to invasive meningococcal disease (IMD) isolates, which can be readily serogrouped, carriage isolates often lack capsule expression, making standard phenotypic assays unsuitable for strain characterization. Several antibody-based methods were evaluated for their abilities to serogroup isolates and were compared with two genotyping methods (real-time PCR [rt-PCR] and whole-genome sequencing [WGS]) to identify which approach would most accurately ascertain the polysaccharide groups associated with carriage isolates. WGS and rt-PCR were in agreement for 99% of IMD isolates, including those with coding sequences for MnB, MnC, MnW, and MnY, and the phenotypic methods correctly identified serogroups for 69 to 98% of IMD isolates. In contrast, only 47% of carriage isolates were groupable by genotypic methods, due to mutations within the capsule operon; of the isolates identified by genotypic methods, ≤43% were serogroupable with any of the phenotypic methods tested. These observations highlight the difficulties in the serogrouping and capsular genogrouping of meningococcal carriage isolates. Based on our findings, WGS is the most suitable approach for the characterization of meningococcal carriage isolates.

Simultaneous single-tube PCR-based assay for the direct identification of the five most common meningococcal serogroups from clinical samples

This study presents a stepdown multiplex PCR assay for the simultaneous detection of the five most common Neisseria meningitidis serogroups (A, B, C, W-135 and Y) in 530 clinical samples obtained from 428 patients (271 blood and 259 cerebrospinal fluid). The sensitivity and the specificity was calculated to 100% [positive predictive value 100% (95%, CI 99.0-100%) and negative predictive value 100% (95% CI 99.0-100%)]. The overall effectiveness permits the rapid, accurate and inexpensive detection of the five most prevalent meningococcal serogroups in clinical samples. It is potentially a valuable tool for diagnosis and epidemiological monitoring of disease due to N. meningitidis.

Design and integration of an all-in-one biomicrofluidic chip

We demonstrate a highly integrated microfluidic chip with the function of DNA amplification. The integrated chip combines giant electrorheological-fluid actuated micromixer and micropump with a microheater array, all formed using soft lithography. Internal functional components are based on polydimethylsiloxane (PDMS) and silvercarbon black-PDMS composites. The system has the advantages of small size with a high degree of integration, high polymerase chain reaction efficiency, digital control and simple fabrication at low cost. This integration approach shows promise for a broad range of applications in chemical synthesis and biological sensinganalysis, as different components can be combined to target desired functionalities, with flexible designs of different microchips easily realizable through soft lithography.

Consecutive use of two multiplex PCR-based assays for simultaneous identification and determination of capsular status of nine common Neisseria meningitidis serogroups associated with invasive disease

We developed two Neisseria meningitidis multiplex PCR assays to be used consecutively that allow determination of the serogroup and capsular status of serogroup A, B, C, 29E, W135, X, and Y cnl-3/cnl-1-like-containing N. meningitidis isolates by direct analysis of the amplicon size. These assays offer a rapid and simple method of serogrouping N. meningitidis.

Serological specificities of murine hybridoma monoclonal antibodies against Neisseria meningitidis serogroups B, C, Y, and W135 and evaluation of their usefulness as serogrouping reagents by indirect whole-cell enzyme-linked immunosorbent assay

Murine hybridoma monoclonal antibodies (MAbs) were produced against the capsular antigens of serogroups B, C, Y, and W135 meningococci. Each serogroup-specific MAb reacted with the extracted capsular polysaccharide from its homologous serogroup only and did not react with capsules from the other three serogroups. The application of these MAbs for serogroup identification of meningococci was demonstrated by their abilities to correctly identify 183 clinical isolates of 185 meningococci recovered from individual invasive meningococcal disease (IMD) patients during routine surveillance in 2002. The remaining two meningococci were identified by PCR grouping as C in one case and Y in another, but neither isolate was positive by bacterial agglutination using rabbit antisera or by enzyme-linked immunosorbent assay using MAbs. The specificities of the anti-Y and anti-W135 MAbs were further assessed by tests with 37 serogroup W135 and 106 serogroup Y meningococci recovered from IMD cases during 1999 to 2001 and 2003. All 143 meningococci except one serogroup Y isolate were correctly identified by positive reactions with the corresponding MAbs that identified their homologous serogroups. The single serogroup Y isolate was received as nonagglutinable and tested as negative with both rabbit anti-Y antiserum and anti-Y MAb but was positive for the serogroup Y-specific siaD gene. The advantage of using MAbs for serogrouping of meningococci is discussed.

Real-time Fluorescent PCR Techniques to Study Microbial-Host Interactions

This chapter describes how real-time polymerase chain reaction (PCR) performs and how it may be used to detect microbial pathogens and the relationship they form with their host. Research and diagnostic microbiology laboratories contain a mix of traditional and leading-edge, in-house and commercial assays for the detection of microbes and the effects they impart upon target tissues, organs, and systems. The PCR has undergone significant change over the last decade, to the extent that only a small proportion of scientists have been able or willing to keep abreast of the latest offerings. The chapter reviews these changes. It discusses the second-generation of PCR technology-kinetic or real-time PCR, a tool gaining widespread acceptance in many scientific disciplines but especially in the microbiology laboratory.

PCR-based assay for detection of Neisseria meningitidis capsular serogroups 29E, X, and Z

PCR-based assays for the identification of Neisseria meningitidis serogroups 29E, X, and Z by detection of specific regions of the ctrA gene are described. The specificities of these assays were confirmed using serogroups A, B, C, 29E, H, W135, X, Y, and Z and nongroupable meningococcal isolates.

Real-time PCR in the microbiology laboratory

Use of PCR in the field of molecular diagnostics has increased to the point where it is now accepted as the standard method for detecting nucleic acids from a number of sample and microbial types. However, conventional PCR was already an essential tool in the research laboratory. Real-time PCR has catalysed wider acceptance of PCR because it is more rapid, sensitive and reproducible, while the risk of carryover contamination is minimised. There is an increasing number of chemistries which are used to detect PCR products as they accumulate within a closed reaction vessel during real-time PCR. These include the non-specific DNA-binding fluorophores and the specific, fluorophore-labelled oligonucleotide probes, some of which will be discussed in detail. It is not only the technology that has changed with the introduction of real-time PCR. Accompanying changes have occurred in the traditional terminology of PCR, and these changes will be highlighted as they occur. Factors that have restricted the development of multiplex real-time PCR, as well as the role of real-time PCR in the quantitation and genotyping of the microbial causes of infectious disease, will also be discussed. Because the amplification hardware and the fluorogenic detection chemistries have evolved rapidly, this review aims to update the scientist on the current state of the art. Additionally, the advantages, limitations and general background of real-time PCR technology will be reviewed in the context of the microbiology laboratory.

Use of real-time PCR to resolve slide agglutination discrepancies in serogroup identification of Neisseria meningitidis

Neisseria meningitidis is a leading cause of bacterial meningitis and septicemia in children and young adults in the United States. Rapid and reliable identification of N. meningitidis serogroups is crucial for judicious and expedient response to cases of meningococcal disease, including decisions about vaccination campaigns. From 1997 to 2002, 1,298 N. meningitidis isolates, collected in the United States through the Active Bacterial Core surveillance (ABCs), were tested by slide agglutination serogrouping (SASG) at both the ABCs sites and the Centers for Disease Control and Prevention (CDC). For over 95% of isolates, SASG results were concordant, while discrepant results were reported for 58 isolates. To resolve these discrepancies, we repeated the SASG in a blinded fashion and employed ctrA and six serogroup-specific PCR assays (SGS-PCR) to determine the genetic capsule type. Seventy-eight percent of discrepancies were resolved, since results of the SGS-PCR and SASG blinded study agreed with each other and confirmed the SASG result at either state health laboratories or CDC. This study demonstrated the ability of SGS-PCR to efficiently resolve SASG discrepancies and identified the main cause of the discrepancies as overreporting of these isolates as nongroupable. It also reemphasized the importance of adherence to quality assurance procedures when performing SASG and prompted prospective monitoring for SASG discrepancies involving isolates collected through ABCs in the United States.