Biology subjects

Keiser, J.

Publications and source records attributed to Keiser, J..

9 recordsLinked to original sources

bioRxiv2026

The antiparasitics ivermectin and moxidectin trigger genomic and transcriptomic adaptation in bacteria

The macrocyclic lactone anthelmintics ivermectin and moxidectin are widely used for parasite control and show antibacterial activity in vitro. Given their structural relatedness to macrolide antibiotics, their broad use raises concerns about macrolide cross-resistance and altered bacterial physiology, yet the impact on gut bacterial isolates and underlying mechanisms remains poorly defined. Here, we combined Oxford Nanopore whole genome sequencing with Illumina RNA sequencing across six bacterial isolates analyzed as unexposed controls and as derivatives repeatedly exposed to ivermectin or moxidectin to identify genomic and transcriptomic signatures associated with exposure to these drugs. High-quality genome assemblies enabled integrated analyses across species with distinct cellular architectures and antimicrobial resistance gene arsenals. Across the panel, exposure was associated with i) widespread modulation of ribosome-linked genes and pathways, the molecular target of macrolide antibiotics; ii) context-dependent tuning of pre-existing antimicrobial resistance gene arsenals, such as macB and mdlB; and iii) recurrent alterations in potassium transport systems (ktrA and trkA). These findings suggest that repeated ivermectin or moxidectin exposure can reshape bacterial physiology in ways that may, in specific genetic backgrounds, co-modulate resistance-associated traits.

microbiology↗

bioRxiv2025

Hybrid-metagenomics reveal off-target effects of albendazole, ivermectin-albendazole and moxidectin-albendazole on the human gut bacteria.

The human whipworm parasite, Trichuris trichiura, poses a critical public health problem, affecting over 400 million people globally and responding poorly to the standard-of-care - benzimidazole chemotherapy. Recent efforts aimed at developing improved treatment options, the two macrolide-benzimidazole combination therapies ivermectin-albendazole and moxidectin-albendazole. Recent reports suggest that ivermectin and moxidectin possess antibacterial properties in vitro, hence there is a need to comprehensively characterize their off-target effects on the gut microbiome. In the framework of a randomized-controlled trial we collected stool samples of 204 T. trichiura-infected individuals in Cote dIvoire receiving albendazole (400mg), albendazole-ivermectin (400mg/200{micro}g/kg) and albendazole-moxidectin (400mg/8mg). Using a state-of-the-art hybrid sequencing approach that combines Illumina short read and Oxford Nanopore long read shotgun sequencing, we recovered over 800 high-quality metagenome-assembled genomes. Our analyses reveal that albendazole and albendazole-moxidectin induce taxonomic shifts in the gut microbiota with only mild functional consequences. In contrast, in individuals receiving higher quantities of albendazole-ivermectin (ivermectin > 12mg), based on their weight, we observed profoundly modulated taxonomic composition and microbial function, while the resistome was largely spared. These findings robustly confirm ivermectins antibacterial properties in the human gut, extending beyond previously reported in vitro effects. Given that ivermectin is a cornerstone in parasitic disease control, it is crucial to evaluate its broader impacts and considering more targeted, evidence-based treatment strategies.

genomics↗

bioRxiv2024

Nanopore-based analysis unravels the genetic landscape and phylogenetic placement of human-infecting Trichuris species in Cote d'Ivoire, Tanzania, Uganda, and Laos

Soil-transmitted helminthiases, particularly trichuriasis, affect over 500 million people, mostly in low- and middle-income countries. Traditional diagnostics fail to distinguish between Trichuris species, obscuring transmission patterns and treatment outcomes. Using nanopore-based full-length ITS2 rDNA sequencing, we analyzed 687 samples from Cote dIvoire, Laos, Tanzania, and Uganda, confirming the phylogenetic placement of Trichuris trichiura and the recently described Trichuris incognita. We identified two genetically distinct Trichuris species infecting humans, with divergent geographic patterns and presence in non-human primates, suggesting complex host-parasite dynamics. Within-country genetic variation indicated local adaptation and cryptic population structure. Importantly, we demonstrated that ITS2 fragment length is a robust, cost-effective diagnostic marker for differentiating T. incognita and T. trichiura, offering a practical alternative to sequencing for resource-limited settings. These findings expose the hidden complexity of Trichuris infections and highlight the urgent need to update diagnostic and control strategies to account for overlooked species diversity in endemic regions.

genomics↗

bioRxiv2024

Discovery of a novel albendazole-ivermectin refractory Trichuris species, T. hominis, in C&ocircte d'Ivoire patients through fecal DNA metabarcoding

Albendazole-ivermectin combination therapy is a promising alternative to benzimidazole monotherapy for Trichuris trichiura control. We used fecal DNA metabarcoding to genetically characterize Trichuris populations in patients from a clinical trial showing lower albendazole-ivermectin efficacy in Cote dIvoire (ERR below 70%) than in Lao PDR and Tanzania (ERR above 98%). ITS-1 and ITS-2 rDNA metabarcoding revealed the entire Cote dIvoire Trichuris population was phylogenetically distinct from T. trichiura in Lao PDR and Tanzania, and more closely related to the porcine parasite Trichuris suis. Complete mitogenomes of eight adult Trichuris from Cote dIvoire confirmed their species-level differentiation. Corresponding Trichuris ITS-1 and ITS-2 sequences in NCBI from individual human patients in Cameroon and Uganda and three captive non-human primates suggest this newly recognized species, T. incognita, is distributed beyond Cote dIvoire and has zoonotic potential. Further work is needed to assess the impact of this Trichuris species on soil transmitted helminth control programs.

genomics↗

bioRxiv2024

Genetic makeup of Trichuris hominibus, a novel Trichuris species naturally infecting humans and displaying signs of resistance to drug treatment

BackgroundTrichuriasis is a neglected tropical disease that affects as many as 500 million individuals and can cause significant morbidity. For decades, it was thought to be caused by one species of whipworm, Trichuris trichiura. Significant differences in response rates to the best available anthelmintic treatment for trichuriasis -- a combination of albendazole and ivermectin -- exist across clinical trial reports yet the underlying reasons are unclear. MethodsCombining long- and short- read sequencing approaches, we assembled a high- quality reference genome of T. incognita n. sp. isolated in an interventional study conducted in Cote dIvoire. The species tree of the Trichuris genus was constructed using 12434 orthologous groups. We sequenced a total of 747 individual worms which were used to confirm the phylogenetic placement and investigate patterns of adaptation through comparative genomic analysis. FindingsHere, we present and characterize a human-infecting Trichuris species that we named Trichuris incognita n. sp. Comparative genomic analysis of genes suspected to confer resistance to either albendazole or ivermectin in helminths revealed a high number of beta- tubulin (TBB) orthologs, present in the whole population of T. incognita n. sp., compared to the canonical T. trichiura species, but these genes were not associated to a resistant phenotype. We conducted a genome wide association study (GWAS) comparing 179 albendazole-ivermectin sensitive to 542 drug non-sensitive worms, which did not conclusively show an adaptation to drug pressure within the same species. InterpretationOur results demonstrate that trichuriasis can be caused by multiple species of whipworm and that the differences in response rates, may be a result of species responding differently to drug treatment, as opposed to an establishment of resistance. This discovery, coupled with the high tolerability of T. incognita n. sp. to albendazole-ivermectin marks a significant shift in how we understand and approach whipworm infections. FundingEuropean Research Council (ERC) Nr. 101019223. Research in context Panel: Evidence before this studyThe recommended treatment with the benzimidazoles albendazole or mebendazole shows consistently low efficacy against T. trichiura, and therefore combination chemotherapy of benzimidazoles and ivermectin has been recommended. Recent clinical trials with albendazole-ivermectin, showed especially low cure rates against what was presumed to be T. trichiura in Cote dIvoire, in contrast to higher efficacy observed in Laos and Pemba, Tanzania. Amplicon sequencing data pointed towards underlying genomic differences and potentially a new species of human infecting Trichuris in Cote dIvoire. Added value of this studyWe identified and described a morphologically indistinguishable, novel causative agent of trichuriasis that doesnt respond to conventional drug treatment: Trichuris incognita n. sp. We provide a high-quality reference genome of this novel species and sequencing data of 747 individual isolates. A genome wide association study did not conclusively show adaptation to drug pressure. This study demonstrates that trichuriasis can be caused by multiple species of whipworm and that the differences in response rates, may be a result of species responding differently to drug treatment, as opposed to an establishment of resistance. Implications of all the available evidenceThe current whole body of evidence calls for new effective treatments against T. incognita n. sp. Due to the morphological indistinguishableness, molecular diagnostic tools need to be implemented to identify species level differences as opposed to the traditional Kato Katz method. The geographical distribution of T. incognita as well as longitudinal changes of species distributions will need to be mapped, in addition to better understanding of the new species pathology and transmission dynamics.

genomics↗

bioRxiv2024

A novel barcoded nanopore sequencing workflow of high-quality, full-length bacterial 16S amplicons for taxonomic annotation of bacterial isolates and complex microbial communities

IntroductionDue to recent improvements, Nanopore sequencing has become a promising method for experiments relying on amplicon sequencing. We describe a flexible workflow to generate and annotate high-quality, full-length 16S rDNA amplicons. We evaluated it for two applications, namely, i) identification of bacterial isolates and ii) species-level profiling of microbial communities. MethodsBacterial isolate identification by sequencing was tested on 47 isolates and compared to MALDI-TOF MS. 97 isolates were additionally sequenced to assess the resolution of phylogenetic classification. Species-level community profiling was tested with two full-length 16S primer pairs (A and B) with custom barcodes and compared to results obtained with Illumina sequencing using 27 stool samples. Finally, a Nextflow pipeline was developed to produce high-quality reads and taxonomically annotate them. ResultsWe found high agreement between our workflow and MALDI-TOF data for isolate identification (PPV = 0.90, Cramers V = 0.857 and, Theils U = 0.316). For species-level community profiling, we found strong correlations (rs > 0.6) of alpha diversity indices between the two primer sets and Illumina sequencing. At the community level, we found significant but small differences when comparing sequencing techniques. Finally, we found moderate to strong correlation when comparing relative abundances of individual species (average rs = 0.6 and 0.533, for primers A and B). DiscussionThe proposed workflow enabled accurate identification of single bacterial isolates, making it a worthwhile alternative to MALDI-TOF. While shortcomings have been identified, it enabled reliable identification of prominent features in microbial communities at a fraction of the cost of Illumina sequencing. ImportanceA quick, robust, simple, and cost-effective method to identify bacterial isolates and communities in each sample is indispensable in the fields of microbiology and infection biology. Recent technological advances in Oxford Nanopore Technologies sequencing make this technique an attractive option considering the adaptability, portability, and cost-effectiveness of the platform. Here, we validated a flexible workflow to identify bacterial isolates and characterize bacterial communities using the Oxford Nanopore Technologies sequencing platform combined with the most recent v14 chemistry kits. For bacterial isolates, we compared our nanopore-based approach to MALDI-TOF MS-based identification. For species-level profiling of complex bacterial communities we compared our nanopore-based approach to Illumina shotgun sequencing. For reproducibility purposes, we wrapped the code used to process the sequencing data into a ready-to-use and self-contained Nextflow pipeline.

microbiology↗

bioRxiv2024

Exposure of gut bacterial isolates to the anthelminthic drugs, ivermectin and moxidectin, leads to antibiotic-like phenotypes of growth inhibition and adaptation.

Due to their broad-spectrum activities, ivermectin and moxidectin are widely used anthelminthics in veterinary and human medicine. However, ivermectin has recently been shown to perturbate gut-microbial growth. Given the macrolide-like structure of both ivermectin and moxidectin, there is a need to characterize the antibiotic spectrum of these anthelminthic drugs and their potential implications in the development of cross-resistance to macrolides and other families of antibiotics. Here, we incubated 59 bacterial isolates representing different clades frequently found in the gut with ivermectin and moxidectin at different concentrations for 16-72h. Further, we challenged 10 bacterial isolates with repeated and gradually increasing concentrations of these two anthelminthics and subsequently characterized their sensitivity to different antibiotics as well as ascending anthelminthic concentrations. We found, that antibacterial activity of the two anthelminthics is comparable to a selection of tested antibiotics, as observed by potency and dose dependence. Bacterial anthelminthic challenging in vitro resulted in decreased anthelminthic sensitivity. Further, adaptation to anthelminthics is associated with decreased antibiotic sensitivity towards three macrolides, a lincosamide, a fluoroquinolone, a tetracycline and two carbapenems. The observed change in bacterial sensitivity profiles is associated with - and likely caused by - repeated anthelminthic exposure. Hence, current and future large-scale administration of ivermectin and moxidectin, respectively, for the control of helminths and malaria raises serious concerns - and hence potential off-target effects should be carefully monitored.

microbiology↗

bioRxiv2022

A Nematode-Selective Potentiator of Organophosphate and Carbamate Agrochemicals

Nematode parasites of humans, livestock and crops pose a significant burden on human health and welfare. Alarmingly, parasitic nematodes of animals have rapidly evolved resistance to anthelmintic drugs, and traditional nematicides that protect crops are facing increasing restrictions because of poor phylogenetic selectivity. Here, we present a pipeline that exploits multiple motor outputs of the model nematode C. elegans for nematicide discovery. This pipeline yielded multiple compounds that selectively kill and/or immobilize diverse nematode parasites. We focus on one compound that induces violent convulsions and paralysis that we call Nementin. We find that Nementin agonizes neuronal dense core vesicle release, which in turn agonizes cholinergic signaling. Consequently, Nementin synergistically enhances the potency of widely-used non-selective acetylcholinesterase inhibitors (AChEIs), but in a nematode-selective manner. Nementin therefore has the potential to reduce the environmental impact of toxic AChEI pesticides used to control nematode infections and infestations. Significance StatementParasitic nematodes pose a considerable burden to human health and food security. Small molecules that have traditionally been used to control these parasites have either been banned because of toxicity concerns or are being rendered ineffective because of the evolution of resistance. Significant gaps in our nematicidal toolkit are therefore becoming an alarming problem. Here, we describe our discovery of Nementin, a small molecule that disrupts the nematode nervous system but is ineffective against non-targeted organisms. We find that Nementin also enhances the activity of non-selective pesticides but does so in a nematode-selective manner. Hence, Nementin is an innovative solution to combat parasitic nematodes in a safe and phylum-selective manner. One-Sentence SummaryA C. elegans-based screening pipeline identifies a selective nematicide that also potentiates acetylcholinesterase inhibitors.

pharmacology and toxicology↗

bioRxiv2020

Structural requirements for dihydrobenzoxazepinone anthelmintics: actions against medically important and model parasites - Trichuris muris, Brugia malayi and Heligmosomoides polygyrus

Nine hundred million people are infected with the soil-transmitted helminths Ascaris lumbricoides (roundworm), hookworm, and Trichuris trichiura (whipworm). However, low single-dose cure rates of the benzimidazole drugs, the mainstay of preventative chemotherapy for whipworm, together with parasite drug resistance, mean that current approaches may not be able to eliminate morbidity from Trichuriasis. We are seeking to develop new anthelmintic drugs specifically with activity against whipworm as a priority, and previously identified a hit series of dihydrobenzoxazepinone (DHB) compounds that block motility of ex vivo Trichuris muris. Here we report a systematic investigation of the structure-activity relationship of the anthelmintic activity of DHB compounds. We synthesised 47 analogues, which allowed us to define features of the molecules essential for anthelmintic action, as well as broadening the chemotype by identification of dihydrobenzoquinolinones (DBQ) with anthelmintic activity. We investigated the activity of these compounds against other parasitic nematodes, identifying DHB compounds with activity against Brugia malayi and Heligmosomoides polygyrus. We also demonstrated activity of DHB compounds against the trematode Schistosoma mansoni, a parasite that causes schistosomiasis. These results demonstrate the potential of DHB and DBQ compounds for further development as broad-spectrum anthelmintics. Author summaryAround a billion people are infected by the soil transmitted helminths Ascaris, hookworm and whipworm. In the case of whipworm, the benzimidazole drugs, which are distributed to school children in affected areas, have low cure rates. This means that finding an improved treatment for whipworm is a priority. We previously identified five DHB compounds in a screen for new compounds active against whipworm. Here we systematically dissect these molecules, making 47 modified versions of the compounds. This allowed us to define the features of these compounds that are important for activity against whipworm. We also demonstrate activity of DHB compounds against other parasitic nematodes, and against Schistosoma mansoni, a trematode parasite. These results show the potential for further development of DHB compounds as broad-spectrum anthelmintics.

pharmacology and toxicology↗