Lemrani, M. | Search bioRxiv

bioRxiv2025

Direct genome sequencing of Leishmania tropica in tissues of Moroccan patients with cutaneous leishmaniasis reveals micro-focal transmission underlain by clonal and sexual reproduction modes

Leishmania tropica is causing cutaneous leishmaniasis (CL) from North Africa to India and in Ethiopia and is reported to be transmitted from humans to humans through sand fly bites. While this species is characterized by a high genetic diversity all over the area of endemicity, there is very little information on diversity at micro-epidemiological scale. Here, we zoomed on an epidemic Moroccan focus of CL - restricted in space and time - and studied transmission patterns by comparative genomics of parasites in human patients. We used a culture-independent method of genome sequencing based on Leishmania genome capture (SureSelect-sequencing, SuSL-seq), applied directly on dermal scrapings. We first compared the genome of paired samples: i.e. parasites in host tissues analyzed by SuSL-seq and derived isolates shortly maintained in culture and analyzed by whole genome sequencing (WGS). Despite the low passage number of isolates, significant differences were observed between karyotypes of 4/7 paired samples, highlighting the clinical and epidemiological relevance of direct genome sequencing. Secondly, we identified 7 groups of nearly identical genotypes, characteristic of clonal propagation as well as parasites with mixed ancestry, a signature of genetic exchange. Our results reveal a micro-focal transmission among humans, underlain by clonal and sexual reproductive modes. This study demonstrates the power of direct genome sequencing for evolutionary genetics at a micro-epidemiological scale.

genomics↗

bioRxiv2023

A comparative genomics approach reveals a local genetic signature of Leishmania tropica in Morocco

In Morocco, cutaneous leishmaniasis (CL) caused by Leishmania (L.) tropica is an important health problem. Despite its high incidence in the country, the genomic heterogeneity of these parasites is still incompletely understood. In this study, we sequenced the genomes of 14 Moroccan isolates of L. tropica collected from confirmed cases of CL to investigate their genomic heterogeneity. Comparative genomics analyses were conducted by applying the recently established Genome Instability Pipeline (GIP), which allowed us to conduct phylogenomic and PCA analyses, and to assess genomic variations at the levels of the karyotype, gene copy number, and single nucleotide polymorphisms (SNPs). The results identified a core group of 12 isolates that were genetically highly related but evolutionarily distant to the reference genome as judged by the presence of over 100,000 SNPs, 75% of which were shared inside this core group. In addition, we identified two highly divergent strains, M3015 and Ltr_16, that were phylogenetically distinct between each other as well as to the core group and the reference genome. Read-depth analysis revealed important karyotypic variations across all isolates and uncovered important differences in gene copy number between the isolates of the core group and the L. tropica reference genome, as well as between the core group and M3015. In conclusion, our NGS results suggest the presence of a local SNP signature that distinguishes Moroccan L. tropica from other endemic regions and from the reference genome. These results pave the way for future research with a larger number of strains that will allow to correlate diverse phenotypes (resistance to treatments, virulence) and origins (geography, host species, year of isolation) to defined genomic signals that may represent interesting biomarker candidates.

genomics↗