Diversity of meningococci associated with invasive meningococcal disease in the Republic of Ireland over a 19 year period, 1996-2015.

Désirée E Bennett,Kenneth L Meyler,Mary T Cafferkey,Robert J Cunney,Daniela Flavia Hozbor

doi:10.1371/journal.pone.0228629

Désirée E Bennett, Kenneth L Meyler + Show 3 more

Open Access

https://doi.org/10.1371/journal.pone.0228629

Copy DOI

Abstract

This study examined the capsular phenotype and genotype of invasive meningococcal disease (IMD)-associated Neisseria meningitidis recovered in the Republic of Ireland (RoI) between 1996 and 2015. This time period encompasses both pre- (when IMD was hyperendemic in the RoI) and post- meningococcal serogroup C conjugate (MCC) vaccine introduction. In total, 1327 isolates representing over one-third of all laboratory-confirmed cases of IMD diagnosed each epidemiological year (EY), were characterised. Serogroups B (menB) and C (menC) predominated throughout, although their relative abundance changed; with an initial increase in the proportion of menC in the late 1990s followed by their dramatic reduction post-MCC vaccine implementation and a concomitant dominance of menB, despite an overall decline in IMD incidence. While the increase in menC was associated with expansion of specific clonal-complexes (cc), cc11 and cc8; the dominance of menB was not. There was considerable variation in menB-associated cc with declines in cc41/44 and cc32, and increases in cc269 and cc461, contributing to a significant increase in the clonal diversity of menB isolates over the study. This increase in diversity was also displayed among the serosubtyping data, with significant declines in proportions of menB isolates expressing p1.4 and p1.15 antigens. These data highlight the changing diversity of IMD-associated meningococci since 1996 in the RoI and emphasise the need for on-going surveillance particularly in view of the recent introduction of a menB vaccine.

Highlights

Neisseria meningitidis (“meningococcus”) is the causative agent of invasive meningococcal disease (IMD) which is responsible for considerable morbidity and mortality throughout the world [1,2]
A total of 1327 N. meningitidis isolates, each recovered from a separate patient with laboratory confirmed IMD, were received by the Irish Meningitis and Sepsis Reference Laboratory (IMSRL) between 1st July 1996 and 30th June 2015, a period of 19 epidemiological year (EY) (Fig 1)
There was a decline in the numbers of isolates received each EY since (Table 1), with a range of 20 to 34 isolates received per EY over the last 5 EY

Summary

Introduction

Neisseria meningitidis (“meningococcus”) is the causative agent of invasive meningococcal disease (IMD) which is responsible for considerable morbidity and mortality throughout the world [1,2]. Invasive meningococcal disease associated strain diversity in Republic of Ireland increasing from 9.3 per 100,000 total population in epidemiological year (EY; July 1 –June 30) 1997/1998 to 11.6 per 100,000 in EY1999/2000 [4]. During this time disease was predominately associated with serogroups B (menB) and C (menC) [3,4]. Since the meningococcal serogroup C conjugate (MCC) vaccine was introduced to the routine childhood immunisation schedule in the RoI in October 2000, incidence rates for all forms of IMD (not just serogroup C disease) continuously declined to 1.5 per 100,000 in EY2015/2016 [4], with disease due to menB accounting for >90% of all IMD since 2003, all largely associated with sporadic cases [4]. Given the diverse nature of menB meningococci in terms of clonal complex distribution [5], it is necessary to accurately define the population of menB strains circulating in the RoI to better assess changes in the epidemiology of meningococcal disease over time, to permit the most efficient allocation of resources and formulation of the most effective disease control and prevention policies

Objectives

Methods

Results

Discussion

Conclusion