Analysis of the twenty-six largest outbreaks of tuberculosis in Aragon using whole-genome sequencing for surveillance purposes.

The incidence of tuberculosis in Aragon, Spain, is around ten cases per 100,000 inhabitants. Since 2004, a molecular surveillance protocol has been carried out; therefore, all M. tuberculosis strains are genotyped. Recently, whole-genome sequencing has been implemented for relevant isolates. The aim of this work is to characterise at the molecular level the causative strains of the 26 largest outbreaks of the community (including ten or more cases), genotyped by IS6110-RFLP and causing 26% of tuberculosis cases. To achieve this objective, two or three isolates of each IS6110-cluster belonging to different years were selected for sequencing. We found that strains of lineages L4.8, L4.3 and L4.1.2 were the most frequent. The threshold of 12 SNPs as the maximum distance for confirming the belonging to an outbreak was met for 18 of the 26 IS6110-clusters. Four pairs of isolates with more than 90 SNPs were identified as not belonging to the same strain, and four other pairs were kept in doubt as the number of SNPs was close to 12, between 14 and 35. The study of Regions of Difference revealed that they are lineage conserved. Moreover, we could analyse the IS6110 locations for all genome-sequenced isolates, finding some frequent locations in isolates belonging to the same lineage and certain IS6110 movements between the paired isolates. In the vast majority, these movements were not captured by the IS6110-RFLP pattern. After classifying the genes containing SNP by their functional category, we could confirm that the number of SNPs detected in genes considered as virulence factors and the number of cases the strain produced were not related, suggesting that a particular SNP is more relevant than the number. The characteristics found in the most successful strains in our community could be useful for other researchers in epidemiology, virulence and pathogenesis.

The MtZ Strain: Molecular Characteristics and Outbreak Investigation of the Most Successful Mycobacterium tuberculosis Strain in Aragon Using Whole-Genome Sequencing.

Since 2004, a tuberculosis surveillance protocol has been carried out in Aragon, thereby managing to detect all tuberculosis outbreaks that take place in the community. The largest outbreak was caused by a strain named Mycobacterium tuberculosis Zaragoza (MtZ), causing 242 cases as of 2020. The main objective of this work was to analyze this outbreak and the molecular characteristics of this successful strain that could be related to its greater transmission. To do this, we first applied whole-genome sequencing to 57 of the isolates. This revealed two principal transmission clusters and six subclusters arising from them. The MtZ strain belongs to L4.8 and had eight specific single nucleotide polymorphisms (SNPs) in genes considered to be virulence factors [ptpA, mc3D, mc3F, VapB41, pks15 (two SNPs), virS, and VapC50]. Second, a transcriptomic study was carried out to better understand the multiple IS6110 copies present in its genome. This allowed us to observe three effects of IS6110: the disruption of the gene in which the IS6110 is inserted (desA3), the overexpression of a gene (ppe38), and the absence of transcription of genes (cut1:Rv1765c) due to the recombination of two IS6110 copies. Finally, because of the disruption of ppe38 and ppe71 genes by an IS6110, a study of PE_PGRS secretion was carried out, showing that MtZ secretes these factors in higher amounts than the reference strain, thereby differing from the hypervirulent phenotype described for the Beijing strains. In conclusion, MtZ consists of several SNPs in genes related to virulence, pathogenesis, and survival, as well as other genomic polymorphisms, which may be implicated in its success among our population.

Clinical Outcome in Human T-Lymphotropic Virus Type 2 Carriers Following Organ Transplantation.

BACKGROUND: Frequent and rapid development of myelopathy has been reported in individuals with human T-lymphotropic virus type 1 (HTLV-1) infection following solid organ transplantation. There is no information regarding HTLV-2, a closely related virus that often infects injection drug users. METHODS: This study includes a retrospective analysis of all consecutive organ transplants performed during the last 2 decades at a large reference transplantation unit in Spain. All participants were tested for anti-HTLV antibodies. RESULTS: A total of 2019 individuals were tested for HTLV during the study period, including 663 potential donors and 1356 recipient candidates. Twelve (0.59%) were reactive on initial HTLV serologic screening, but only 6 (all recipients) were confirmed as positive, all for HTLV-2. Two recipients underwent liver transplantation and have remained asymptomatic despite being on tacrolimus for 4 and 8 years, respectively. Likewise, the remaining 4 HTLV-2 carriers have not developed clinical complications potentially associated with HTLV-2. CONCLUSIONS: Unlike HTLV-1 infection, HTLV-2 infection in the transplantation setting does not seem to be associated with rapid development of neurologic complications, Given the cross-seroreactivity between HTLV-1 and HTLV-2, discriminatory rapid tests are urgently needed and would reduce unnecessary organ discharge.