Rapid detection of Neisseria meningitidis in cerebrospinal fluid by one-step polymerase chain reaction of the nspA gene

Accurate, fast and cost-effective simultaneous detection of bacterial meningitis by qualitative PCR with high-resolution melting

Neisseria meningitidis, Haemophilus influenzae and Streptococcus pneumoniae are leading causes of meningitis and acute invasive infections. PCR-based methods are widely used for the diagnosis and surveillance of bacterial pathogens because of their high sensitivity, specificity and high-throughput capabilities compared with conventional laboratory methods. This study evaluated a high-resolution melting qualitative PCR analysis method for the simultaneous detection of these three pathogens. The assay has been optimized to detect three species-specific genes of each organism isolated from clinical samples, enabling accurate identification of the etiological agent. The method proved to be highly sensitive and cheaper than the real-time PCR TaqMan^® system because it is probe-free; it could be used for the diagnosis of invasive diseases in public health laboratories of developing countries.

Characterization of strains of Neisseria meningitidis causing meningococcal meningitis in Mozambique, 2014: Implications for vaccination against meningococcal meningitis

INTRODUCTION

In sub Saharan Africa, the epidemiology, including the distribution of serogroups of strains of N. meningitidis is poorly investigated in countries outside "the meningitis belt". This study was conducted with the aim to determine the distribution of serogroups of strains of N. meningitidis causing meningococcal meningitis in children and adults in Mozambique.

METHODS

A total of 106 PCR confirmed Neisseria meningitidis Cerebrospinal Fluid (CSF) samples or isolates were obtained from the biobank of acute bacterial meningitis (ABM) surveillance being implemented by the National Institute of Health, at three central hospitals in Mozambique, from January to December 2014. Serogroups of N. meningitidis were determined using conventional PCR, targeting siaD gene for Neisseria meningitidis. Outer Membrane Proteins (OMP) Genotyping was performed by amplifying porA gene in nine samples.

RESULTS

Of the 106 PCR confirmed Neisseria meningitidis samples, the most frequent serotype was A (50.0%, 53/106), followed by W/Y (18.9%, 20/106), C (8.5%, 9/106), X (7.5%, 8/106) and B (0.9%, 1/106). We found non-groupable strains in a total of 15 (14.2%) samples. PorA genotypes from nine strains showed expected patterns with the exception of two serogroup C strains with P1.19,15,36 and P1.19-36,15 and one serogroup X with P1.19,15,36, variants frequently associated to serogroup B.

CONCLUSION

Our data shows that the number of cases of meningococcal meningitis routinely reported in central hospitals in Mozambique is significant and the most dominant serogroup is A. In conclusion, although serogroup A has almost been eliminated from the "meningitis belt", this serogroup remains a major concern in countries outside the belt such as Mozambique.

Fatal case of co-infection with dengue virus and Neisseria meningitidis during a dengue epidemic in the state of Rio de Janeiro, Brazil

INTRODUCTION

Dengue and meningococcal disease are caused by two different agents: a flavivirus and a Gram-negative bacterium, respectively. The first symptoms of both diseases can be indistinct and a rapid and accurate diagnosis is crucial, considering that both diseases are associated with high morbidity and mortality, representing a major public-health problem in Brazil.

CASE PRESENTATION

We report a fatal case of co-infection of dengue virus (DENV) and Neisseria meningitidis in a 54-year-old patient. The serum tested positive for DENV NS1 antigen, and N. meningitidis serogroup C was detected by nspA-PCR. Following the initial positive result for DENV infection, rRT-PCRwas performed and DENV-4 was confirmed.

CONCLUSION

Our report highlights the importance of accurate differential diagnosis during periods of high circulation of DENV, in order to provide adequate management and an improved outcome.

COMPARISON OF METHODS TO IDENTIFY Neisseria meningitidis IN ASYMPTOMATIC CARRIERS

Neisseria meningitidis is a cause of several life-threatening diseases and can be a normal commensal in the upper respiratory tract of healthy carriers. The carrier rate is not well established especially because there is no standard method for the isolation of N. meningitidis. Therefore, the aim of this study was to compare identification methods for the carrier state. Two swabs were collected from 190 volunteers: one was cultured and the other had DNA extracted directly from the sample. The Polymerase Chain Reaction (PCR) was performed to determine species and serogroups and compared the results between the methods. PCR for species determination used two pairs of primers and when there was only one amplicon, it was sequenced. The culture technique was positive in 23 (12.1%) subjects while the direct extraction method was positive in 132 (69.5%), p < 0.001. Among the 135 subjects with positive N. meningitides tests, 88 (65.2%) were serogroup C; 3 (2.2%) serogroup B; 5 (3.7%) were positive for both serogroup B and C, and 39 (28.9%) did not belong to any of the tested serogroups. In this study, PCR from DNA extracted directly from swabs identified more N. meningitidis asymptomatic carriers than the culture technique.

Comparison of PCR-based methods for the simultaneous detection of Neisseria meningitidis, Haemophilus influenzae, and Streptococcus pneumoniae in clinical samples

Background

Several in-house PCR-based assays have been described for the detection of bacterial meningitis caused by Neisseria meningitidis, Streptococcus pneumoniae, and Haemophilus influenzae from clinical samples. PCR-based methods targeting different bacterial genes are frequently used by different laboratories worldwide, but no standard method has ever been established. The aim of our study was to compare different in-house and a commercial PCR-based tests for the detection of bacterial pathogens causing meningitis and invasive disease in humans.

Methods

A total of 110 isolates and 134 clinical samples (99 cerebrospinal fluid and 35 blood samples) collected from suspected cases of invasive disease were analyzed. Specific sets of primers frequently used for PCR-diagnosis of the three pathogens were used and compared with the results achieved using the multiplex approach described here. Several different gene targets were used for each microorganism, namely ctrA, crgA and nspA for N. meningitidis, ply for S. pneumoniae, P6 and bexA for H. influenzae.

Results

All used methods were fast, specific and sensitive, while some of the targets used for the in-house PCR assay detected lower concentrations of genomic DNA than the commercial method. An additional PCR reaction is described for the differentiation of capsulated and non-capsulated H. influenzae strains, the while commercial method only detects capsulated strains.

Conclusions

The in-house PCR methods here compared showed to be rapid, sensitive, highly specific, and cheaper than commercial methods. The in-house PCR methods could be easily adopted by public laboratories of developing countries for diagnostic purposes. The best results were achieved using primers targeting the genes nspA, ply, and P6 which were able to detect the lowest DNA concentrations for each specific target.

Replacement of Neisseria meningitidis C cc11/ET-15 variant by a cc103 hypervirulent clone, Brazil 2005-2011

Outbreaks caused by serogroup C meningococci in the northeast region of Brazil from 2005 to 2011 were associated to the emergence of variant ET-15 of cc11, which has been replaced by cc103 from 2006 to date. The increase of cc103 should be closely monitored to prevent the spread of this clone to neighbouring regions.

Engineered polymer-supported synthesis of 3'-carboxyalkyl-modified oligonucleotides and their applications in the construction of biochips for diagnosis of the diseases

An engineered polymer support 5 has been prepared for the solid-phase assembly of 3'-carboxyalkyl-modified oligonucleotides using commonly available reagents. A two-step deprotection procedure resulted in the quantitative cleavage of oligonucleotides from the support and removal of the protecting groups from phosphodiesters and exocyclic amino groups of the nucleic bases. The fully deprotected oligomers, obtained in high yield, were desalted and analyzed on RP-HPLC. After characterization by MALDI-TOF, these carboxyalkylated oligonucleotides were immobilized onto the epoxy-functionalized glass microslides to prepare biochips. The performance of these biochips was evaluated under different sets of conditions and then successfully validated by the detection of base mismatches and human infectious disease, bacterial meningitis, caused by N. meningitidis.

Quest for a broad-range vaccine against Neisseria meningitidis serogroup B: implications of genetic variations of the surface-exposed proteins

Despite the development of new vaccine formulations using new biotechnology resources to combat emerging and re-emerging diseases, serogroup B meningococcal disease is still a worldwide burden, accounting for many deaths and disabilities every year. The successful approach of coupling a polysaccharide (PS) with a carrier protein in order to increase long-lasting immunity could not be exploited againstNeisseria meningitidisB because of the limitations of using the capsular PS of serogroup B meningococci. Tailor-made vaccines based on exposed proteins were shown to be a promising approach to overcome these flaws. However, the continuous adaptation of surface meningococcal structures to the external environment has led to genetic shifts of potential vaccine-target epitopes, hampering the quest for a broad-range vaccine that could be used against all serogroups, especially against serogroup B.

Neisseria meningitidis PorA variable regions: rapid detection of P1.7 and P1.19 variants by PCR

AIM

Rapid characterization of variable region (VR)1 variants of the porA gene among invasive strains is crucial for outbreak management and epidemiology studies. Recent sequence analysis studies in Brazil showed that the VR1 P1.7 and P1.19 variants are highly prevalent, accounting for 68%, of the total number of VR1 variants characterized. The aim of this work is to develop a rapid polymerase chain reaction (PCR)-based method for genosubtyping Neisseria meningitidis by detection of porA variable regions P1.7 and P1.19.

METHODS AND RESULTS

PCR primers for the detection of porA VR1 P1.7 and P1.19 were designed and tested using 198 clinical N. meningitidis isolates that had been previously evaluated by porA sequencing. All 50 strains with VR1 P1.7 and all 65 strains with VR1 P1.19 were positively identified by the respective VR-specific PCR and no false-positive reactions occurred.

CONCLUSIONS

VR-specific PCR amplification accurately identified VR P1.7 and P1.19 strains.

SIGNIFICANCE AND IMPACT OF THE STUDY

To overcome the disadvantages of serosubtyping and sequencing for typing the porA VR1 segment of N. meningitidis, we developed a PCR-based method to rapidly and accurately detect VR1 P1.7 and P1.19 variants. This approach is highly specific and sensitive; moreover it may allow for genotype determination of culture-negative samples.

Scaling up of PCR-based surveillance of bacterial meningitis in the African meningitis belt: indisputable benefits of multiplex PCR assay in Niger

The absence of reliable laboratories for culture of Neisseria meningitidis, Haemophilus influenzae and Streptococcus pneumoniae, the three main causes of bacterial meningitis in Africa, hampers microbiological surveillance in these countries. To compensate for this situation in Niger, a multiplex single-tube PCR method has been implemented at a central level to test cerebrospinal fluid (CSF) samples. The overall confirmation rate for PCR (N=3791) was 40.8% compared with 16.0% for culture (N=945) (P<10(-6)). Among 850 CSF specimens tested by both methods, the overall confirmation rate was 29.4% for PCR and 16.4% for culture (P<10(-8)). PCR was also efficient for the CSF specimens stored in Trans-isolate medium. In conclusion, PCR assay is currently a key tool in Africa to improve microbiological surveillance of bacterial meningitis.

Multilocus sequence typing and repetitive element-based polymerase chain reaction analysis of Neisseria meningitidis isolates in Brazil reveal the emergence of 11 new sequence types genetically related to the ST-32 and ST-41/44 complexes and high prevalence of strains related to hypervirulent lineages

Eighty-four strains of Neisseria meningitidis isolated from patients with meningococcal disease in 4 states of Brazil were analyzed by multilocus sequence typing and repetitive element-based polymerase chain reaction (Rep-PCR). The majority of strains analyzed (82%) belonged to 4 hypervirulent lineages, and 11 of 20 new sequence type (STs) characterized were related to hypervirulent lineages. Sequences of fetA and porA genes were analyzed, and the majority were related to profiles present in the ST-32 complex/electrophoretic type (ET)-5 complex. Rep-PCR analysis showed a unique electrophoretic pattern among strains related to hypervirulent lineages. Considering that 81% of the strains were serogroup B and strains belonging to the ST-32/ET-5 complex are genetically related to the Cuban vaccine strain used in a mass vaccination from 1990 to 1994 in Brazil, we believe that this vaccine did not confer effective herd immunity even among the age group within the vaccine showed higher efficacy. Our results once more raise the question about which strains should be used in the development of a new vaccine against N. meningitidis serogroup B.