Infectivity of Mycobacterium tuberculosis Genotypes and Outcome of Contact Investigation in Classroom in Guangxi, China.

Dongxiang Pan,Xi Long,Prasit Palittapongarnpim,Dingwen Lin,Rushu Lan,Liwen Huang,Angkana Chaiprasert,Huifang Qin,Edward Mcneil,Virasakdi Chongsuvivatwong,Mei Lin,Xiaoqiang Qiu

doi:10.1155/2019/3980658

Abstract

Objective To evaluate the infectivity of Mycobacterium tuberculosis (M.tb) genotypes of index cases in the classroom of adolescent schools in Guangxi, China. Methods Adolescent school tuberculosis (TB) contact investigations were conducted for all reported index TB cases from November 2016 to December 2017 in Guangxi, China. Genotypes of index cases and contact cases were identified by 15-loci mycobacterial interspersed repetitive units–variable number tandem repeat and spoligotyping. Outcome variable was 5 levels' order of tuberculin skin test (TST) results to new active TB [0-5 mm, 6-9 mm, 10-14 mm, ≥ 15 mm (without TB), and ≥15 mm (with TB)]. Multivariate ordered logistic regression analysis was performed to evaluate the independent effect of genotypes of index case on contact screening outcome. Results Beijing genotype occurred more commonly in female index patients. One genotypic cluster of two index cases and one cluster of two contact cases were detected. The association between infectivity of Beijing genotype of index cases and outcome of contact investigation was statistically significant in univariate analysis but no so after adjustment for characteristics of contacts and sex of index cases (P value=0.057). Female index cases increased the chance for TB infection/being active TB among contacts (ordinal odds ratio = 1.39, 95% confidence interval: 1.21, 1.60). Contacts who studied in the middle school, who with non-Han ethnicity and who without BCG scar had increased risk for TB infection/being active TB. Conclusion There was not enough evidence from our data to support that Beijing strains were more infective than non-Beijing strains in TB transmission in school setting.

Highlights

Tuberculosis (TB) is an infectious disease caused by the bacillus Mycobacterium tuberculosis (M.tb)
We aimed to evaluate genotypes of M. tb of the index cases and the outcome of contact investigation and to test the assumption whether the Beijing family of the index case was more infectious to school contacts than non-Beijing genotypes after adjustment with various epidemiological factors, such as school type, sex, ethnicity, and clinical characteristics
Sputum positive acid-fast bacillus (AFB) smears were reported in 35.9% (42/117) of the indexed cases

Summary

Introduction

Tuberculosis (TB) is an infectious disease caused by the bacillus Mycobacterium tuberculosis (M.tb). It was estimated that approximately 1.7 billion people (approximately onequarter of the world’s population) were latently infected with M.tb globally [1]. Prevention of new infections of M.tb and their progression to TB disease is critical to reduce the burden of disease and death caused by TB and to achieve the End TB Strategy targets set for 2030 and 2035 [2]. The Beijing genotype family was well recognized as a distinct genetic lineage and the major concern of M.tb [4].

Methods

Results

Conclusion