A snapshot of genetic lineages of Mycobacterium tuberculosis in Ireland over a two-year period, 2010 and 2011

M M Fitzgibbon,D O’Flanagan,J O’Donnell,T R Rogers,E Roycroft,S Jackson,N Gibbons

doi:10.2807/ese.18.03.20367-en

M M Fitzgibbon, D O’Flanagan + Show 5 more

Open Access

https://doi.org/10.2807/ese.18.03.20367-en

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Abstract

Mycobacterial interspersed repetitive-unit-variable-number tandem repeat typing alone was used to investigate the genetic lineages among 361 Mycobacterium tuberculosis strains circulating in Ireland over a two-year period, 2010 and 2011. The majority of isolates, 63% (229/361), belonged to lineage 4 (Euro-American), while lineages 1 (Indo-Oceanic), 2 (East-Asian) and 3 (East-African–Indian) represented 12% of isolates each (42/361, 45/361, and 45/361, respectively). Sub-lineages Beijing (lineage 2), East-African–Indian (lineage 1) and Delhi/central-Asian (lineage 3) predominated among foreign-born cases, while a higher proportion of Euro-American lineages were identified among cases born in Ireland. Eighteen molecular clusters involving 63 tuberculosis (TB) cases were identified across four sub-lineages of lineage 4. While the mean cluster size was 3.5 TB cases, the largest cluster (involving 12 Irish-born cases) was identified in the Latin American–Mediterranean sub-lineage. Clustering of isolates was higher among Irish-born TB cases (47 of 63 clustered cases), whereas only one cluster (3/63) involved solely foreign-born individuals. Four multidrug-resistant cases identified during this period represented lineages 2 and 4. This study provides the first insight into the structure of the M. tuberculosis population in Ireland.

Highlights

Tuberculosis (TB) caused by Mycobacterium tuberculosis remains a serious challenge to public health worldwide
Some 361 M. tuberculosis isolates were recovered in or referred to the Irish Mycobacteria Reference Laboratory (IMRL) during 2010–11, representing 63.6% of culture-positive cases identified through the national TB surveillance system in that period
The majority (63%) belonged to lineage 4 (Euro-American), while lineages 1 (Indo-Oceanic), 2 (East-Asian) and 3 (East-African–Indian) represented 12% each

Summary

Introduction

Tuberculosis (TB) caused by Mycobacterium tuberculosis remains a serious challenge to public health worldwide. Multidrug-resistant (MDR) TB continues to be a major problem and an added burden in highincidence countries such as Romania (108.2/100,000) and the Baltic states Lithuania (62.1/100,000), Latvia (43.2/100,000) and Estonia (30.7/100,000) [1]. In Ireland, TB is a statutorily notifiable disease, and in a recent report on the epidemiology of TB in the country, the proportion of culture-confirmed TB cases was 71.2% in 2009 and 63.2% in 2010 (data from 2010 were not finalised at the time of submission) [3]. These proportions are similar to those reported for previous years [3]

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