Can we, should we, eradicate the meningococcus?

Identification of the nasopharyngeal carriage of Neisseria meningitidis by 16S rRNA Gene sequencing in asymptomatic adolescents and young adults in Cartagena, Colombia (2019–2020)

The bacterium Neisseria meningitidis, a strictly human pathogen, can cause meningitis, meningococcemia, sepsis, and death; repeatedly it scause outbreaks around the world. The frequency of asymptomatic carriage is often high in adolescents and young adults, increasing the invasive meningococcal disease risk and likelihood of transmission. However, detailed analyses of meningococcal carriage in this population in Colombia, particularly in coastal areas, are lacking. In this study, the prevalence and characteristics of Neisseria meningitidis carriage were evaluated in asymptomatic adolescents and young adults (11-25 years old) in Cartagena, Colombia. Oropharynx samples were collected from participants between August and December 2019. The phenotypic identification of bacteria was performed by conventional methods and biochemical testing. Molecular identification to the species level was performed by 16S rRNA gene sequencing. In total, 12 of 648 samples were positive for Neisseria meningitidis by 16S rRNA sequencing, indicating a prevalence of 1.9%. Isolates were classified into four invasive serogroups (A, B, C, and W) by a comparative sequence analysis of the ribosomal gene. Despite the occurrence of meningococcal disease in Cartagena city in the last several years, the frequency of oropharyngeal carriage in adolescents and young adults was low. Serogroup A had not been previously reported in nasopharyngeal samples in Colombia. This is the first report of Neisseria meningitidis on the Colombian Caribbean coast based on 16S rRNA sequencing and is expected to guide the development of vaccination and follow-up strategies.

Vaccination strategies for the prevention of meningococcal disease

Routine prophylactic vaccination and mass vaccination strategies have been used to control both endemic and epidemic disease caused by Neisseria meningitidis globally. This review discusses real-world examples of these vaccination strategies, their implementation, and outcomes of these efforts, with the overall goal of providing insights on how to achieve optimal control of meningococcal disease through vaccination in varied settings. Tailoring immunization programs to fit the needs of the target population has the potential to optimally reduce disease incidence.

Uncovering oral Neisseria tropism and persistence using metagenomic sequencing

Microbial epidemiology and population genomics have previously been carried out near-exclusively for organisms grown in vitro. Metagenomics helps to overcome this limitation, but it is still challenging to achieve strain-level characterization of microorganisms from culture-independent data with sufficient resolution for epidemiological modelling. Here, we have developed multiple complementary approaches that can be combined to profile and track individual microbial strains. To specifically profile highly recombinant neisseriae from oral metagenomes, we integrated four metagenomic analysis techniques: single nucleotide polymorphisms in the clade's core genome, DNA uptake sequence signatures, metagenomic multilocus sequence typing and strain-specific marker genes. We applied these tools to 520 oral metagenomes from the Human Microbiome Project, finding evidence of site tropism and temporal intra-subject strain retention. Although the opportunistic pathogen Neisseria meningitidis is enriched for colonization in the throat, N. flavescens and N. subflava populate the tongue dorsum, and N. sicca, N. mucosa and N. elongata the gingival plaque. The buccal mucosa appeared as an intermediate ecological niche between the plaque and the tongue. The resulting approaches to metagenomic strain profiling are generalizable and can be extended to other organisms and microbiomes across environments.

Impact of calcium signaling during infection of Neisseria meningitidis to human brain microvascular endothelial cells

The pili and outer membrane proteins of Neisseria meningitidis (meningococci) facilitate bacterial adhesion and invasion into host cells. In this context expression of meningococcal PilC1 protein has been reported to play a crucial role. Intracellular calcium mobilization has been implicated as an important signaling event during internalization of several bacterial pathogens. Here we employed time lapse calcium-imaging and demonstrated that PilC1 of meningococci triggered a significant increase in cytoplasmic calcium in human brain microvascular endothelial cells, whereas PilC1-deficient meningococci could not initiate this signaling process. The increase in cytosolic calcium in response to PilC1-expressing meningococci was due to efflux of calcium from host intracellular stores as demonstrated by using 2-APB, which inhibits the release of calcium from the endoplasmic reticulum. Moreover, pre-treatment of host cells with U73122 (phospholipase C inhibitor) abolished the cytosolic calcium increase caused by PilC1-expressing meningococci demonstrating that active phospholipase C (PLC) is required to induce calcium transients in host cells. Furthermore, the role of cytosolic calcium on meningococcal adherence and internalization was documented by gentamicin protection assay and double immunofluorescence (DIF) staining. Results indicated that chelation of intracellular calcium by using BAPTA-AM significantly impaired PilC1-mediated meningococcal adherence to and invasion into host endothelial cells. However, buffering of extracellular calcium by BAPTA or EGTA demonstrated no significant effect on meningococcal adherence to and invasion into host cells. Taken together, these results indicate that meningococci induce calcium release from intracellular stores of host endothelial cells via PilC1 and cytoplasmic calcium concentrations play a critical role during PilC1 mediated meningococcal adherence to and subsequent invasion into host endothelial cells.

Meningococcal carriage prevalence in university students, 1824 years of age in Santiago, Chile

INTRODUCTION

Neisseria meningitidis invasive disease is a major public health problem. Pharyngeal carriage is considered a prerequisite for invasive infection. Prevalence reaches 10% in general population and up to 30% in the 20-24 years age group. The aim of this study was to asses pharyngeal carriage prevalence in healthy subjects aged 18-24 years, and as secondary endpoints evaluate known risk factors, to identify serogroups and sequence in the isolated strains.

METHODS

Cross-sectional study in 500 healthy subjects; students from Universidad de Chile aged 18-24 years, Santiago, Chile, October 2012. Each subject underwent a risk factor survey prior to throat culture sampling. Samples were processed in one central Microbiology Laboratory of Hospital Luis Calvo Mackenna and serogrouping and sequencing was performed at Instituto de Salud Pública de Chile.

RESULTS

We obtained throat samples from 500 healthy subjects, 20 (4%) positive for N. meningitidis. Of positive strains 20% were serogroup B, 15% W and the rest non groupable. The median age was 20 years, 50% were men. Of the risk factors evaluated, 24% were current smokers, 16% shared a room, 72% had kissed someone during the last month, 64% had gone to pub and 76% had consumed alcohol in the same period of time.

DISCUSSION

Literatures meningococcal carriage prevalence reaches up to 30% in people aged 18-24 years. Prevalence in our study was 4%. Different interpretations could be given; one could be the absence of overcrowding in our students because of the lack of dorms in our scholar system and also the characteristics of our enrolled group.

CONCLUSIONS

Our results suggest the necessity to extend the study to other age groups and to other cities, to better understand the Chilean reality, as well as others regions of America, considering that these results cannot be extrapolated to another countries.

Meningococcal resistance to antimicrobial peptides is mediated by bacterial adhesion and host cell RhoA and Cdc42 signalling

Antimicrobial peptides (AMPs) constitute an essential part of the innate immune defence. Pathogenic bacteria have evolved numerous strategies to withstand AMP-mediated killing. The influence of host epithelia on bacterial AMP resistance is, however, still largely unknown. We found that adhesion to pharyngeal epithelial cells protected Neisseria meningitidis, a leading cause of meningitis and sepsis, from the human cathelicidin LL-37, the cationic model amphipathic peptide (MAP) and the peptaibol alamethicin, but not from polymyxin B. Adhesion to primary airway epithelia resulted in a similar increase in LL-37 resistance. The inhibition of selective host cell signalling mediated by RhoA and Cdc42 was found to abolish the adhesion-induced LL-37 resistance by a mechanism unrelated to the actin cytoskeleton. Moreover, N. meningitidis triggered the formation of cholesterol-rich membrane microdomains in pharyngeal epithelial cells, and host cell cholesterol proved to be essential for adhesion-induced resistance. Our data highlight the importance of Rho GTPase-dependent host cell signalling for meningococcal AMP resistance. These results indicate that N. meningitidis selectively exploits the epithelial microenvironment in order to protect itself from LL-37.

The impact of protein-conjugate polysaccharide vaccines: an endgame for meningitis?

The development and implementation of conjugate polysaccharide vaccines against invasive bacterial diseases, specifically those caused by the encapsulated bacteria Neisseria meningitidis, Haemophilus influenzae and Streptococcus pneumoniae, has been one of the most effective public health innovations of the last 25 years. These vaccines have resulted in significant reductions in childhood morbidity and mortality worldwide, with their effectiveness due in large part to their ability to induce long-lasting immunity in a range of age groups. At the population level this immunity reduces carriage and interrupts transmission resulting in herd immunity; however, these beneficial effects can be counterbalanced by the selection pressures that immunity against carriage can impose, potentially promoting the emergence and spread of virulent vaccine escape variants. Studies following the implementation of meningococcal serogroup C vaccines improved our understanding of these effects in relation to the biology of accidental pathogens such as the meningococcus. This understanding has enabled the refinement of the implementation of conjugate polysaccharide vaccines against meningitis-associated bacteria, and will be crucial in maintaining and improving vaccine control of these infections. To date there is little evidence for the spread of virulent vaccine escape variants of the meningococcus and H. influenzae, although this has been reported in pneumococci.