Summary Background Multidrug-resistant tuberculosis (MDR-TB) is a significant threat to tuberculosis elimination worldwide. Understanding the transmission pattern is crucial for its control. We used a genomic epidemiological approach to assess the recent transmission of MDR-TB and potential risk factors for transmission. Methods In a population-based retrospective study, we performed variable-number-of-tandem-repeat (VNTR) genotyping, followed by whole-genome sequencing (WGS) of isolates from all MDR-TB patients in Shanghai, China, 2009-2012. We measured strain diversity within and between genomically clustered patients. Genomic and epidemiologic data were combined to construct transmission networks. Findings 367 (5%) of 7982 patients with tuberculosis had MDR tuberculosis and 324 (88%) of these had isolates available for genomic analysis. 103 (32%) of the 324 MDR strains were in 38 genomic clusters that differed by 12 or fewer single nucleotide polymorphisms (SNPs), indicating recent transmission of MDR strains. Patients who had delayed diagnosis or were older than 45 years had high risk of recent transmission. 235 (73%) patients with MDR tuberculosis probably had transmission of MDR strains. Transmission network analysis showed that 33 (87%) of the 38 clusters accumulated additional drug-resistance mutations through emergence or fixation of mutations during transmission. 68 (66%) of 103 clustered MDR strains had compensatory mutations of rifampicin resistance. Interpretation Recent transmission of MDR strains, with increasing drug-resistance, helps drive the MDR-TB epidemic in Shanghai, China. WGS provides a measure of the heterogeneity of drug-resistant mutations within and between hosts and enhances our ability to determine the transmission patterns of MDR-TB. Funding National Science and Technology Major Project, National Natural Science Foundation of China, and US National Insitutes of Health.

The Beijing family is the most successful genotype of Mycobacterium tuberculosis and responsible for more than a quarter of the global tuberculosis epidemic. As the predominant genotype in East Asia, the Beijing family has been emerging in various areas of the world and is often associated with disease outbreaks and antibiotic resistance. Revealing the origin and historical dissemination of this strain family is important for understanding its current global success. Here we characterized the global diversity of this family based on whole-genome sequences of 358 Beijing strains. We show that the Beijing strains endemic in East Asia are genetically diverse, whereas the globally emerging strains mostly belong to a more homogenous subtype known as “modern” Beijing. Phylogeographic and coalescent analyses indicate that the Beijing family most likely emerged around 30,000 y ago in southern East Asia, and accompanied the early colonization by modern humans in this area. By combining the genomic data and genotyping result of 1,793 strains from across China, we found the “modern” Beijing sublineage experienced massive expansions in northern China during the Neolithic era and subsequently spread to other regions following the migration of Han Chinese. Our results support a parallel evolution of the Beijing family and modern humans in East Asia. The dominance of the “modern” Beijing sublineage in East Asia and its recent global emergence are most likely driven by its hypervirulence, which might reflect adaption to increased human population densities linked to the agricultural transition in northern China.

A small number of high-burden countries account for the majority of tuberculosis cases worldwide. Detailed data are lacking from these regions. To explore the evolutionary history of M. tuberculosis in China — the third highest TB burden country — we analyzed a countrywide collection of 4,578 isolates. Little genetic diversity was detected within the large M. tuberculosis population in China, with 99.4% of the bacterial population belonging to lineage 2 and three sublineages of lineage 4. The deeply rooted phylogenetic positions and geographic restriction of these four genotypes indicate that their populations expanded in situ following a small number of introductions to China. Coalescent analyses suggest that these bacterial sub-populations emerged in China around 1,000 years ago, expanded in parallel from the 12th century onward, and the whole population peaked in the late 18th century. More recently, sublineage L2.3, which is indigenous to China and exhibited relatively high transmissibility and extensive global dissemination, came to dominate the population dynamics of M. tuberculosis in China. Our results indicate that historical expansion of four M. tuberculosis strains shaped the current TB epidemic in China, and highlight the long-term genetic continuity of the indigenous M. tuberculosis population.

National Natural Science Foundation of China, National Science and Technology Major Project of China, and US National Institutes of Health.

OBJECTIVES: To determine the diagnostic and clinical utility of trio-rapid genome sequencing in critically ill infants. DESIGN: In this prospective study, samples from critically ill infants were analyzed using both proband-only clinical exome sequencing and trio-rapid genome sequencing (proband and biological parents). The study occurred between April 2019 and December 2019. SETTING: Thirteen member hospitals of the China Neonatal Genomes Project spanning 10 provinces were involved. PARTICIPANTS: Critically ill infants (n = 202), from birth up until 13 months of life were enrolled based on eligibility criteria (e.g., CNS anomaly, complex congenital heart disease, evidence of metabolic disease, recurrent severe infection, suspected immune deficiency, and multiple malformations). INTERVENTIONS: None. MEASUREMENTS AND MAIN RESULTS: Of the 202 participants, neuromuscular (45%), respiratory (22%), and immunologic/infectious (18%) were the most commonly observed phenotypes. The diagnostic yield of trio-rapid genome sequencing was higher than that of proband-only clinical exome sequencing (36.6% [95% CI, 30.1–43.7%] vs 20.3% [95% CI, 15.1–26.6%], respectively; p = 0.0004), and the average turnaround time for trio-rapid genome sequencing (median: 7 d) was faster than that of proband-only clinical exome sequencing (median: 20 d) (p < 2.2 × 10–16). The metagenomic analysis identified pathogenic or likely pathogenic microbes in six infants with symptoms of sepsis, and these results guided the antibiotic treatment strategy. Sixteen infants (21.6%) experienced a change in clinical management following trio-rapid genome sequencing diagnosis, and 24 infants (32.4%) were referred to a new subspecialist. CONCLUSIONS: Trio-rapid genome sequencing provided higher diagnostic yield in a shorter period of time in this cohort of critically ill infants compared with proband-only clinical exome sequencing. Precise and fast molecular diagnosis can alter medical management and positively impact patient outcomes.

Compensatory mutations have been suggested to promote multidrug-resistant tuberculosis (MDR-TB) transmission, but their role in facilitating the recent transmission of MDR-TB is unclear. To investigate the epidemiological significance of compensatory mutations, we analyzed a four-year population-based collection of MDR-TB strains from Shanghai (the most populous city in China) and 1346 published global MDR-TB strains. We report that MDR-TB strains with compensatory mutations in the rpoA, rpoB, or rpoC genes were neither more frequently clustered nor found in larger clusters than those without compensatory mutations. Our results suggest that compensatory mutations are not a major contributor to the current epidemic of MDR-TB.

Mixed infection by multiple Mycobacterium tuberculosis (MTB) strains is associated with poor treatment outcome of tuberculosis (TB). Traditional genotyping methods have been used to detect mixed infections of MTB, however, their sensitivity and resolution are limited. Deep whole-genome sequencing (WGS) has been proved highly sensitive and discriminative for studying population heterogeneity of MTB. Here, we developed a phylogenetic-based method to detect MTB mixed infections using WGS data. We collected published WGS data of 782 global MTB strains from public database. We called homogeneous and heterogeneous single nucleotide variations (SNVs) of individual strains by mapping short reads to the ancestral MTB reference genome. We constructed a phylogenomic database based on 68,639 homogeneous SNVs of 652 MTB strains. Mixed infections were determined if multiple evolutionary paths were identified by mapping the SNVs of individual samples to the phylogenomic database. By simulation, our method could specifically detect mixed infections when the sequencing depth of minor strains was as low as 1× coverage, and when the genomic distance of two mixed strains was as small as 16 SNVs. By applying our methods to all 782 samples, we detected 47 mixed infections and 45 of them were caused by locally endemic strains. The results indicate that our method is highly sensitive and discriminative for identifying mixed infections from deep WGS data of MTB isolates.

Background Enzyme-based host depletion significantly improves the sensitivity of clinical metagenomics. Recent studies found that real-time adaptive sequencing of DNA molecules was achieved using a nanopore sequencing machine, which enabled effective enrichment of microbial sequences. However, few studies have compared the enzyme-based host depletion and nanopore adaptive sequencing for microbial enrichment efficiency. Results To compare the host depletion and microbial enrichment efficiency of enzyme-based and adaptive sequencing methods, the present study collected clinical samples from eight children with respiratory tract infections. The same respiratory samples were subjected to standard methods, adaptive sequencing methods, enzyme-based host depletion methods, and the combination of adaptive sequencing and enzyme-based host depletion methods. We compared the host depletion efficiency, microbial enrichment efficiency, and pathogenic microorganisms detected between the four methods. We found that adaptive sequencing, enzyme-based host depletion and the combined methods significantly enriched the microbial sequences and significantly increased the diversity of microorganisms (p value < 0.001 for each method compared to standard). The highest microbial enrichment efficiency was achieved using the combined method. Compared to the standard method, the combined method increased the microbial reads by a median of 113.41-fold (interquartile range 23.32–327.72, maximum 1812), and the number of genera by a median of 70-fold (interquartile range 56.75–86.75, maximum 164). The combined method detected 6 pathogens in 4 samples with a median read of 547, compared to 5 pathogens in 4 samples with a median read of 4 using the standard method. Conclusion The combined method is an effective, easy-to-run method for enriching microbial sequences in clinical metagenomics from sputum and bronchoalveolar lavage fluid samples and may improve the sensitivity of clinical metagenomics for other host-derived clinical samples.