Mycobacterium tuberculosis is less likely to acquire pathogenic mutations during latent infection than during active disease.

Most people infected with Mycobacterium tuberculosis (Mtb) are believed to be in a state of latent tuberculosis (TB) infection (LTBI). Although LTBI is asymptomatic and not infectious, there is a risk of developing active disease even decades after infection. Here, to characterize mutations acquired during LTBI, we collected and analyzed Mtb genomes from seven Japanese patient pairs, each pair consisting of two active TB patients whose starting dates of developing active disease were >3 years apart; one had a high suspicion of LTBI before developing active disease, whereas the other did not. Thereafter, we compared these genomes with those of longitudinal sample pairs within a host of chronic active TB infections combined with public data. The bacterial populations in patients with LTBI were genetically more homogeneous and accumulated single nucleotide polymorphisms (SNPs) slower than those from active disease. Moreover, the lower proportion of nonsynonymous SNPs indicated weaker selective pressures during LTBI than active disease. Finally, the different mutation spectrums indicated different mutators between LTBI and active disease. These results suggest that the likelihood of the acquisition of mutations responsible for antibiotic resistance and increased virulence was lower in the Mtb population from LTBI than active disease.IMPORTANCEControlling latent tuberculosis (TB) infection (LTBI) activation is an effective strategy for TB elimination, where understanding Mycobacterium tuberculosis (Mtb) dynamics within the host plays an important role. Previous studies on chronic active disease reported that Mtb accumulated genomic mutations within the host, possibly resulting in acquired drug resistance and increased virulence. However, several reports suggest that fewer mutations accumulate during LTBI than during the active disease, but the associated risk is largely unknown. Here, we analyzed the genomic dynamics of Mtb within the host during LTBI. Our results statistically suggest that Mtb accumulates mutations during LTBI, but most mutations are under low selective pressures, which induce mutations responsible for drug resistance and virulence. Thus, we propose that LTBI acts as a source for new TB disease rather than as a period for in-host genome evolution.

Aortic endograft infection by Mycobacterium abscessus subsp. massiliense with acquired clarithromycin resistance: a case report.

BACKGROUND: Mycobacterium abscessus subsp. massiliense (MMA) comprises a group of non-tuberculous, rapidly growing mycobacteria. Although MMA can cause pulmonary diseases, surgical site infections, and disseminated diseases, aortic endograft infection has not been reported. Here, we describe the first case of aortic endograft infection caused by MMA. CASE PRESENTATION: Two months after stent-graft insertion for an abdominal aortic aneurysm, an 85-year-old man was admitted with fever and abdominal pain and was diagnosed with aortic endograft infection. Despite 14 days of meropenem and vancomycin intravenous administration, periaortic fluid pooling increased as compared to that before antibiotic administration. The abscess was drained, and fluorescent acid-fast staining of the abscess fluid revealed bacilli. We conducted genetic tests on the genes hsp65, rpoB, and sodA, performed Whole Genome Sequencing (WGS), and identified the organism as MMA. Intravenous imipenem-cilastatin (IPM/CS), amikacin (AMK), and oral clarithromycin (CAM) were administered. After 2 months, oral CAM and sitafloxacin were administered because the abscess had decreased in size. However, after 6 weeks, the abscess increased in size again. Antimicrobial susceptibility testing of the drainage fluid from the abscess resulted in the isolation of an MMA strain that had acquired resistance to CAM. Intravenous IPM/CS, AMK, and oral linezolid were added to the treatment regimen along with oral CAM and STFX. However, he was not fully cured and died 6 months later. Neither the full-length erythromycin ribosome methyltransferase (erm)(41) gene nor the rrl or rpIV gene mutations were found by Sanger sequencing in the pre- and post-treatment strains. Whole-genome sequence analysis of the post-treatment strain revealed mutations in genes with no previous reports of association with macrolide resistance. CONCLUSIONS: Aortic endograft infection caused by MMA strain is extremely rare; nonetheless, MMA should be suspected as the causative microorganism when broad-spectrum antimicrobials are ineffective.

Causative antigens of humidifier lung in vapor from a humidifier: A case report.

A 68-year-old man exhibited fever and cough three weeks prior to hospital admission after three months of ultrasonic humidifier usage. Chest computed tomography showed bilateral ground-glass opacities, lymphocyte levels in the bronchoalveolar lavage fluid were elevated (60.8%), and the histological examination of a transbronchial lung biopsy showed lymphocytic alveolitis. He gradually improved without medication after he stopped using the humidifier. Accordingly, humidifier lung was the diagnosis. Humidifier water and vapor collected from the patient's humidifier were investigated. Humidifier vapor was obtained by collecting the condensed moisture. Laboratory examinations exhibited gram-negative rods and a high concentration of endotoxin and (1 â†’ 3)-ß-D-glucan in both vapor and water. The serum-precipitating antibodies showed a stronger reaction against humidifier vapor than against humidifier water. 16S rRNA metagenomic analysis revealed a high percentage of sequences of Spirosoma lacussanchae and Sphingomonas spp. in both the humidifier vapor and water. The percentages of sequence reads were lower in humidifier vapor than in water; conversely, sequences of Pseudomonas spp. and Allorhizobium-Neorhizobium-Pararhizobium-Rhizobium were more concentrated in the humidifier vapor than in humidifier water. Although the reason for the different bacterial ratios between humidifier vapor and water is uncertain, the bacteria that were more concentrated in humidifier vapor than in humidifier water might have been the causative antigen underlying the humidifier lung diagnosis. This is the first report to indicate the presence of causative antigens in humidifier vapor.

Complete Genome Sequences of 14 Nontuberculous Mycobacteria Type Strains.

Here, we present the complete genome sequences of 14 nontuberculous mycobacteria type strains. The addition of type strain data may provide a concrete basis for further research.

In vitro activity of tedizolid and linezolid against multidrug-resistant Mycobacterium tuberculosis: a comparative study using microdilution broth assay and genomics.

The effects of tedizolid (TZD) against multidrug-resistant Mycobacterium tuberculosis isolates were investigated. This is possibly the first study to evaluate the MIC of TZD against Japanese Mycobacterium tuberculosis isolates. As TZD had a significantly lower MIC than LZD (P < 0.01), it was suggested to be a better, non-toxic alternative to LZD.

Development of a nucleic acid chromatography assay for the detection of commonly isolated rapidly growing mycobacteria.

Introduction. Non-tuberculosis mycobacterium infections are increasing worldwide, including those caused by rapidly growing mycobacteria (RGM).Gap Statement. The identification of the aetiological agent in the context of infections is essential for the adoption of an adequate therapeutic approach. However, the methods for the rapid distinction of different RGM species are less than optimal.Aim. To develop a nucleic acid chromatography kit to identify clinically common RGM.Methodology. We tried to develop a nucleic acid chromatography kit designed to detect four RGM species (including three subspecies) i.e. Mycobacterium abscessus subsp. abscessus, Mycobacterium abscessus subsp. bolletii (detected as M. abscessus/bolletii) Mycobacterium abscessus subsp. massiliense, Mycobacterium fortuitum, Mycobacterium chelonae and Mycobacterium peregrinum. The amplified target genes for each species/subspecies using multiplex PCR were analysed using a nucleic acid chromatography assay.Results. Among the 159 mycobacterial type strains and 70 RGM clinical isolates tested, the developed assay correctly identified all relevant RGM without any cross-reactivity or false-negatives. The limits of detection for each species were approximately 0.2 pg µl-1.Conclusion. The rapid and simple nucleic acid chromatography method developed here, which does not involve heat denaturation, may contribute to the rapid identification and treatment of RGM infections.

Systemic transport of trans-zeatin and its precursor have differing roles in Arabidopsis shoots.

Organ-to-organ signal transmission is essential for higher organisms to ensure coordinated biological reactions during metabolism and morphogenesis. Similar to organs in animals, plant organs communicate by various signalling molecules. Among them, cytokinins, a class of phytohormones, play a key role as root-to-shoot long-distance signals, regulating various growth and developmental processes in shoots1,2. Previous studies have proposed that trans-zeatin-riboside, a type of cytokinin precursor, is a major long-distance signalling form in xylem vessels and its action depends on metabolic conversion via the LONELY GUY enzyme in proximity to the site of action3-5. Here we report an additional long-distance signalling form of cytokinin: trans-zeatin, an active form. Grafting between various cytokinin biosynthetic and transportation mutants revealed that root-to-shoot translocation of trans-zeatin, a minor component of xylem cytokinin, controls leaf size but not meristem activity-related traits, whereas that of trans-zeatin riboside is sufficient for regulating both traits. Considering the ratio of trans-zeatin to trans-zeatin-riboside in xylem and their delivery rate change in response to environmental conditions, this dual long-distance cytokinin signalling system allows plants to fine-tune the manner of shoot growth to adapt to fluctuating environments.

Q&A: How do plants respond to cytokinins and what is their importance?

Cytokinins comprise a family of signaling molecules essential for regulating the growth and development of plants, acting both locally and at a distance. Although much is known about their biosynthesis and transport, important open questions remain.

Molecular dissection of the roles of phytochrome in photoperiodic flowering in rice.

Phytochromes mediate the photoperiodic control of flowering in rice (Oryza sativa), a short-day plant. Recent molecular genetics studies have revealed a genetic network that enables the critical daylength response of florigen gene expression. Analyses using a rice phytochrome chromophore-deficient mutant, photoperiod sensitivity5, have so far revealed that within this network, phytochromes are required for expression of Grain number, plant height and heading date7 (Ghd7), a floral repressor gene in rice. There are three phytochrome genes in rice, but the roles of each phytochrome family member in daylength response have not previously been defined. Here, we revealed multiple action points for each phytochrome in the critical daylength response of florigen expression by using single and double phytochrome mutant lines of rice. Our results show that either phyA alone or a genetic combination of phyB and phyC can induce Ghd7 mRNA, whereas phyB alone causes some reduction in levels of Ghd7 mRNA. Moreover, phyB and phyA can affect Ghd7 activity and Early heading date1 (a floral inducer) activity in the network, respectively. Therefore, each phytochrome gene of rice has distinct roles, and all of the phytochrome actions coordinately control the critical daylength response of florigen expression in rice.