Neisseria meningitidis infection: who, when and where?

Abstract

Neisseria meningitidis is a Gram-negative β-proteobacterium responsible for an endemic worldwide infection. The epidemiology and serogroup distribution can change very quickly. The incidence of meningitis infection varies from very rare to more than 1000 cases per 100,000 of the population yearly. The carriage of N. meningitidis, which represents an exclusive human commensal, is asymptomatic, but in rare cases bacteria proliferate in the CNS and rapidly lead to the death of the affected subjects. Host genetic factors, such as single nucleotide polymorphisms, can promote meningococcal disease, being able to influence the individual predisposition to the pathology. Although a reduction in meningococcal disease has been observed in Europe, a continuous surveillance is necessary to control any possible outbreaks of new hypervirulent clones into populations that could modify the epidemiology of meningococcal infections and the clinical spectrum of affected subjects.

Keywords:

• epidemiology
• hypervirulent clonal complexes
• invasive meningococcal disease
• Neisseria meningitidis
• single nucleotide polymorphisms

Financial & competing interests disclosure

The authors have no relevant affiliations or financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending or royalties.

No writing assistance was utilized in the production of this manuscript.

Key issues

• Neisseria meningitidis is characterized by a high degree of antigenic changes, which allows this bacterium, such as many others that infect the CNS, to escape from immunological mechanisms of the host.

• About 10% of the total population has an asymptomatic carriage of N. meningitidis, constituting a commensal diplococcus of the nasopharynx that can last from days to months. One individual can carry more than one meningococcal strain. Rarely, bacteria enter into bloodstream and rapidly proliferate in the CNS, causing invasive meningococcal disease, which is quickly lethal.

• The meningococcal disease remains a serious public worldwide health problem, since an early diagnosis of meningitis is hard due to the similarity of the first phases of the disease to some viral and bacterial diseases. If not promptly recognized and adequately treated, it can be rapidly lethal.

• Genetic factors of the host, such as some single nucleotide polymorphisms in innate determinants, are able to influence the clinical presentation of patients affected by meningococcal infection.

• Since the rather high frequency of some single nucleotide polymorphisms in the general population, the identification of those subjects carrying the variants associated with a higher risk to develop a severe meningococcal disease form or die after contracting N. meningitidis, would represent an important aim.

• The introduction of the routine MenC conjugate vaccination has led to a significant decrease of invasive meningococcal disease incidence in Europe. Currently, this serogroup represents the second most common cause of meningococcal disease after serogroup B. Single clonal complexes belonging to serogroup B are responsible for prolonged outbreaks, lasting a decade or more, characterized by high morbidity and mortality.

• The epidemiology and serogroup distribution can change very quickly. The recent spread of MenX, considered a clone able to cause only sporadic cases until 10 years ago, and serogroup Y in the African Meningitis Belt and in several European and American countries, respectively, demonstrates the need to increase the disease surveillance.

• An enhanced surveillance would be necessary for the rapid identification of new putative virulent and hypervirulent clonal complexes that might represent a serious worldwide health problem.