The Epidemiological Significance and Temporal Stability of Mycobacterial Interspersed Repetitive Units-Variable Number of Tandem Repeats-Based Method Applied to Mycobacterium tuberculosis in China.

Yang Li,Weili Jiang,Mikael Mansjö,Yi Hu,Biao Xu,Qi Zhao,Sven Hoffner,Solomon Ghebremichael

doi:10.3390/ijerph15040782

Abstract

This study aimed to validate the epidemiological significance and temporal stability of Mycobacterial Interspersed Repetitive Units-Variable Number of Tandem Repeats (MIRU-VNTR) typing in a genetically and geographically diverse set of clinical isolates from patients diagnosed with pulmonary tuberculosis in China. Between 2010 and 2013, a total of 982 Mycobacterium tuberculosis isolates were collected from four population-based investigations in China. Apart from the currently applied 24-locus MIRU-VNTR, six additional hypervariable loci were analyzed in order to validate the MIRU-VNTR combinations in terms of their epidemiological links, clustering time span, and paired geographic distance. In vitro temporal stability was analyzed for both individual MIRU-VNTR loci, and for several combinations of loci. In the present study, four MIRU-VNTR combinations, including the hypervariable loci 3820, 3232, 2163a, and 4120, were evaluated. All of these combinations obtained a Hunter-Gaston discriminatory index (HGDI) value over 0.9900 with a reduced clustering proportion (from 32.0% to 25.6%). By comparing epidemiological links, clustering time span, and paired geographic distance, we found that the performances of the four MIRU-VNTR combinations were comparable to the insertion sequence 6110 restriction fragment length polymorphism (IS6110-RFLP), and significantly better than that of 24-locus MIRU-VNTR genotyping alone. The proportion of temporally stable loci ranged from 90.5% to 92.5% within the combined MIRU-VNTR genotyping, which is higher than IS6110-RFLP (85.4%). By adding four hypervariable loci to the standard 24-locus MIRU-VNTR genotyping, we obtained a high discriminatory power, stability and epidemiological significance. This algorithm could therefore be used to improve tuberculosis transmission surveillance and outbreak investigation in China.

Highlights

Tuberculosis (TB) remains an important threat to public health worldwide
Study subjects were defined as TB patients with positive culture results, whose M. tuberculosis isolates were further grown on Löwenstein–Jensen (LJ) medium for up to 4 weeks
The proportion of temporally stable loci ranged from 90.5% to 92.5% within the four MIRU-VNTR

Summary

Introduction

Tuberculosis (TB) remains an important threat to public health worldwide. There has been a steady decline in both the incidence and prevalence of TB in China from 2010 to 2016, TB remains a leading infectious disease [1]. Drug-resistant TB, especially multidrug-resistant (MDR)-TB, has made the control of TB in China even more difficult [2]. The world health organization (WHO) estimated that China’s incidence of TB in 2016 was 64 cases per 100,000 people, of which 8.2%. Were MDR-TB/rifampicin-resistant (RR) TB cases [3]. The molecular epidemiological investigation of Mycobacterium tuberculosis (M. tuberculosis) has significantly increased our understanding of TB epidemiology, and contributed to population-based control of tuberculosis. Molecular genotyping suggests the potential transmission link between TB patients, enabling the identification of outbreaks, and laboratorial cross contamination [4]. Sequencing, e.g., whole genome sequencing, is very promising, but cannot be applied in high-burden

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