Molecular Epidemiology of Mycobacterium tuberculosis in Kiribati

Tuberculosis incidence rates in Kiribati are among the highest in the Western Pacific region, however the diversity of circulating Mycobacterium tuberculosisstrains is largely unknown.

We embarked on a project in collaboration with the Secretariat of the Pacific Community (New Caledonia), Pasteur Institute (New Caledonia) and National Reference Center for Mycobacterium (Germany), to collect data that could be used to inform local public health policy.

This will be the first report of prevailing TB strains in Kiribati. These results will identify prevention approached that should be adopted in Kiribati to reduce the future impact of TB.

Sputum and structured questionnaires were collected from patients presenting with TB symptoms at the central hospital in Kiribati.

Sputum was cultured, isolates genotyped using three methods (RFLP, MIRU-VNTR and spoligotyping) and drug susceptibility testing performed.

TB was cultured from 73 of the 163 recruited patients. Using genotype methods we were able to identify seven phylogenetic lineages (different groups of Mtb strains) including a novel Kiribati strain never identified before.

The Beijing strain lineage that has been linked to drug-resistance in other countries around the world, was most commonly found in the Kiribati cohort (49 per cent). Although we found little evidence of drug resistance in our study sample, we identified that the Beijing strains were linked to over-crowded living conditions in our study population. Furthermore, many strains in our cohort (59 per cent based on IS6110 typing of all strains) clustered, suggesting that there is ongoing transmission of TB in the local community.

We suggest an enhanced case finding among close contacts and continued supervised treatment of all identified cases using standard first-line drugs can assist in reducing the TB burden in Kiribati.