Evaluation of a diagnostic polymerase chain reaction assay for Neisseria meningitidis in North America and field experience during an outbreak

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.

Bacterial meningitis in children under 15 years of age in Nepal

BACKGROUND

Bacterial meningitis in children is a life-threatening problem resulting in severe morbidity and mortality. For the prompt initiation of antibacterial therapy, rapid and reliable diagnostic methods are of utmost importance. Therefore, this study was designed to find out the rate of bacterial pathogens of meningitis from suspected cases by performing conventional methods and latex agglutination.

METHODS

A descriptive type of study was carried out from May 2012 to April 2013. Cerebrospinal fluid (CSF) specimens from 252 suspected cases of meningitis were subjected for Gram staining, bacterial culture and latex agglutination test. The identification of growth of bacteria was done following standard microbiological methods recommended by American Society for Microbiology. Antibiotic sensitivity testing was done by modified Kirby-Bauer disk diffusion method.

RESULTS

From the total 252 suspected cases, 7.2 % bacterial meningitis was revealed by Gram staining and culture methods whereas latex agglutination method detected 5.6 %. Gram-negative organisms contributed the majority of the cases (72.2 %) with Haemophilus influenzae as the leading pathogen for meningitis. Overall, 33.3 % mortality rate was found.

CONCLUSIONS

In conclusion, a significant rate of bacterial meningitis was found in this study prompting concern for national wide surveillance.

Epidemiology, diagnosis, and antimicrobial treatment of acute bacterial meningitis

The epidemiology of bacterial meningitis has changed as a result of the widespread use of conjugate vaccines and preventive antimicrobial treatment of pregnant women. Given the significant morbidity and mortality associated with bacterial meningitis, accurate information is necessary regarding the important etiological agents and populations at risk to ascertain public health measures and ensure appropriate management. In this review, we describe the changing epidemiology of bacterial meningitis in the United States and throughout the world by reviewing the global changes in etiological agents followed by specific microorganism data on the impact of the development and widespread use of conjugate vaccines. We provide recommendations for empirical antimicrobial and adjunctive treatments for clinical subgroups and review available laboratory methods in making the etiological diagnosis of bacterial meningitis. Finally, we summarize risk factors, clinical features, and microbiological diagnostics for the specific bacteria causing this disease.

Polymerase chain reaction for diagnosis and serogrouping of meningococcal disease in children

A prospective study was performed including all children younger than 18 years with the clinical diagnosis of invasive meningococcal disease (IMD) hospitalized at the University Hospital Sant Joan de Déu in Barcelona, Spain, from January 2001 to December 2006. During the study period, 168 meningococcal disease cases were reported. Microbiologic confirmation was obtained in 118 cases. Forty-six (38.9%) of 118 cases were only detected by polymerase chain reaction (PCR); 6 patients were culture positive and PCR negative (5%). Serogroup B predominated in the 6-year period with 83.1% of the strains. A significant decrease in serogroup C was observed in the last 3 years of the study (P=0.029), and less common serogroups, such as serogroup A and W135, emerged. Serogroup distribution of patient diagnoses only by real-time PCR showed a similar distribution: serogroup B, 85.7%; serogroup C, 7.1%; and nontypeable serogroups, 7.1%. In conclusion, real-time PCR is more rapid and sensitive than culture for diagnosis and serogrouping of IMD.

Diagnosis and management of meningococcal disease: the need for centralized care

Meningococcal infection remains a significant health problem in children, with a significant mortality and morbidity. Prompt recognition and aggressive early treatment are the only effective measures against invasive disease. This requires immediate administration of antibiotic therapy, and the recognition and treatment of patients who may have complications of meningococcal infection such as shock, raised intracranial pressure (ICP) or both. Encouragingly, its mortality has fallen in recent years. This is the result of several factors such as the centralization of care of seriously ill children in paediatric intensive care units (PICUs), the establishment of specialized mobile intensive care teams, the development of protocols for the treatment of meningococcal infection, and the dissemination by national bodies and charities of guidance about early recognition and management. We will review the pathophysiology and management of the different presentations of meningococcal disease and examine the possible role of adjunctive therapies.

Rapid genetic grouping of factor h-binding protein (genome-derived neisserial antigen 1870), a promising group B meningococcal vaccine candidate

The most important antigen component of a promising multicomponent group B meningococcal recombinant protein vaccine is based on genome-derived neisserial antigen 1870, which recently was renamed factor H-binding protein (FHBP) to reflect one of its critical functions as a complement regulatory protein. Neisseria meningitidis strains can be subdivided into three FHBP variant groups based on divergence of FHBP amino acid sequences. Within each variant group, amino acid sequences are >90% conserved. To develop an FHBP-based group B vaccine, it is important to know the distribution of FHBP variant 1, 2, and 3 strains in different geographic regions, since antibodies against FHBP are bactericidal against strains within the homologous group but show minimal activity against strains from other groups. We have devised a high-throughput, quantitative PCR-based method that allows rapid and precise assignment of FHBP genes into each of the three major variant lineages. Among 48 group B isolates from patients hospitalized in California in 2003 to 2004, 83%, 13%, and 4%, respectively, had variant 1, 2, and 3 genes. Thus, a vaccine based on the variant 1 protein has the potential to prevent the majority of cases of group B disease. The quantitative PCR-based method will be useful for determining and monitoring the prevalence of meningococcal isolates with genes encoding different FHBP variant proteins. The technique also is suitable for monitoring variation of genes encoding other protein antigens targeted for vaccination.

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.

Simultaneous single-tube PCR assay for the detection of Neisseria meningitidis, Haemophilus influenzae type b and Streptococcus pneumoniae

Rapid, accurate and inexpensive diagnosis of bacterial meningitis is critical for patient management. This study describes the development and evaluation of a multiplex PCR assay for the detection of Neisseria meningitidis, Streptococcus pneumoniae and Haemophilus influenzae type b, which globally account for 90% of cases of bacterial meningitis. The single-tube assay, based on the ctrA, ply and bex targets, respectively, enabled detection of 5-10 pg DNA. When the assay was tested with clinical samples (n = 425), its sensitivity for the three targets was 93.9%, 92.3% and 88%, respectively, while the overall specificity and positive predictive value of the assay was 100%. The negative predictive value was 99.1-99.5%. The methodology permits rapid and accurate detection of the three main pathogens that cause bacterial meningitis.

Rapid and Fatal Meningococcal Disease Due to a Strain of Neisseria meningitidis Containing the Capsule Null Locus

BACKGROUND

Neisseria meningitidis continues to be an important cause of invasive bacterial disease among children and young adults worldwide. In Canada, N. meningitidis strains that bear serogroups B and C polysaccharide capsules predominate. We report the first documented case of invasive meningococcal disease in an immunocompetent host caused by an acapsular strain of N. meningitidis containing the capsule null locus (cnl).

METHODS

Analysis of the isolate was performed with use of serological and molecular methods, including multilocus sequence typing and cnl gene identification. Analysis of 16S ribosomal RNA (rRNA) and porA genes was also performed to confirm the identity of the bacterium.

RESULTS

The patient was a healthy, immunocompetent 13-year-old child, and N. meningitidis was recovered from a sample of her cerebrospinal fluid before death. The isolate was nontypeable by both conventional antisera and indirect whole-cell enzyme-linked immuosorbent assay methods using antibodies to serogroups B, C, Y, and W135. The isolate was further identified as a cnl strain, serotype 15 (ST-198). N. meningitidis-specific DNA was identified in the isolate and in the pre- and postmortem specimens by 16S rRNA and porA gene analysis.

CONCLUSIONS

This is the first reported case of fatal meningococcal disease caused by an acapsular cnl strain of N. meningitidis that was isolated from an immunocompetent host. Routine molecular diagnostic methods targeted at the cnl locus failed to detect this organism, indicating a need to determine the incidence of infection with cnl strains among patients with culture-negative invasive disease.

[Meningococcal disease diagnostic criteria in Greater Metropolitan Campinas, São Paulo State, Brazil]

The aim of this article is to evaluate confirmatory criteria: culture, latex agglutination, counter immunoelectrophoresis, microscopic examination, and clinical/epidemiological criteria for cases of meningococcal disease reported in Greater Metropolitan Campinas, São Paulo State, Brazil, from 1993 to 2002 (568 cases). The following variables were also studied: clinical features, gender, age, city, hospital, case fatality, seasonality, and Neisseria meningitidis serogroup. Culture as a confirmatory criterion was the dependent variable in univariate analysis. The mean proportion of confirmatory criterion by culture was 68.7%. Clinical features of meningococcal disease -- meningitis without septicemia (OR = 2.87; CI: 1.89-4.38) and septicemia without meningitis (OR = 0.26; CI: 0.17-0.45) -- were associated with confirmation by culture. Case fatality rates were different among all diagnostic criteria. More attention should be given to etiological diagnostic confirmation in more severe cases. Diagnostic methods such as PCR may improve etiological confirmation of meningococcal disease in cases with negative cultures.

Acute Bacterial Meningitis in Children

Despite advances in recent decades in management, including new and effective antimicrobials, children with bacterial meningitis still incur significant morbidity and mortality. Pathophysiologic processes including colonization and migration of the bacteria to blood, seeding of the meninges, and meningeal and brain inflammation have been largely elucidated, but more specific knowledge could lead to new effective therapies. Outside of the neonatal period, the most common causative organisms have been Haemophilus influenzae, Streptococcus pneumoniae, and Neisseria meningitidis. However, conjugate vaccines, especially the H influenzae type b preparation, have contributed significantly to steep declines in the incidence of meningitis. Optimal management consists of rapid diagnosis and administration of bactericidal antibiotics with properties allowing adequate penetration of the inflamed blood-brain barrier. Recently, development of microbial resistance has resulted in changes to recommended empiric antibiotic regimens. Novel therapies are under investigation; however, until controlled trials can be conducted, these therapies cannot be recommended.

Bacterial meningitis in children

This review comprises aspects of the epidemiology, microbiology, pathophysiology, clinical manifestations, diagnosis, management, prognosis, and prevention of bacterial meningitis, with emphasis on the paediatric population. The beginning of this millennium has witnessed the virtual disappearance of Haemophilus invasive disease in some countries, emergence of pneumococcal strains that are resistant to multiple antibiotics, isolation of pneumococci with tolerance to vancomycin, outbreaks and clusters of meningococcal meningitis in several geographical areas, and intense research in development of effective conjugate pneumococcal and meningococcal vaccines. Bacterial meningitis has become an uncommon disease in the developed world. Unfortunately, because of limited economic resources and poor living conditions, many developing countries are still affected by the devastating consequences of this life-threatening systemic infection. Basic and clinical research is needed to discover new antimicrobial and anti-inflammatory agents to improve outcome from disease. Novel strategies are needed to distribute and implement effective vaccines worldwide to prevent bacterial meningitis.