Biology subjects

Leon-Sampedro, R.

Publications and source records attributed to Leon-Sampedro, R..

9 recordsLinked to original sources

bioRxiv2026

A humanized Galleria mellonella model reveals prophage-mediated breakdown of colonization resistance against Salmonella

BackgroundColonisation resistance provided by the gut microbiota is a critical barrier to pathogen invasion, yet its study in vivo is constrained by the complexity and cost of vertebrate models. Here, we developed a humanised Galleria mellonella infection model by inoculating wax moth larvae with complex human faecal microbiota. 16S rRNA gene sequencing confirmed stable, reproducible establishment of a diverse human-associated community across larvae over four days. ResultsHumanised larvae exhibited colonisation resistance against Salmonella enterica serovar Typhimurium, with mortality reduced to 20% compared to 90% in non-colonised controls. To test whether prophages could overcome this barrier, we infected larvae with isogenic S. Tm strains differing in the presence of prophage P22. Infection with the P22-carrying strain resulted in a threefold higher larval mortality (60% vs. 20%), increased pathogen load, and a significant reduction in the abundance of resident E. coli. Free P22 virions were detected early after infection, indicating extensive prophage activity. Notably, P22 can neither adsorb nor lyse resident E. coli, indicating that prophage-mediated invasion success did not rely on direct lysis. Instead, using high-throughput metabolic profiling paired with whole genome sequencing of three replicate lineages, we found that phage activation intensified resource-partitioning, accelerating functional metabolic adaptations in E. coli that significantly reduced the niche-overlap between the invading pathogen and the commensal E. coli. ConclusionOur findings establish the first humanised G. mellonella model supporting complex human microbiota and provide a novel non-lytic mechanism by which prophages influence species interactions. This scalable, low-cost model offers a new platform to dissect pathogen-phage-microbiota interactions relevant to human gut ecology.

microbiology↗

bioRxiv2024

Multi-layered ecological interactions determine growth of clinical antibiotic-resistant strains within human microbiomes

Understanding the spread of antibiotic-resistant bacteria in human-associated microbial communities, particularly in the gut microbiome, is critical for combating the global resistance crisis. However, the role of various ecological factors, such as intraspecies or interspecies interactions, in modulating this process is poorly understood. We hypothesized that different strains within the same species would exhibit distinct interactions with the resident microbiota, leading to variable invasion outcomes. To test this, we examined the population growth of multiple clinically relevant antibiotic-resistant E. coli strains carrying ESBL and carbapenemase resistance plasmids. We introduced these strains into human gut microbiome samples from healthy individuals, using replicated anaerobic microcosms treated or untreated with antibiotics. We found that while antibiotic exposure significantly influenced the growth of these incoming strains, some were successful even in the absence of antibiotics. The variation in ecological success across strain-microbiome sample combinations was positively associated with the intrinsic growth capacities of the strains in local abiotic conditions and their competitive interactions with resident E. coli. Furthermore, the incoming resistant strains had strain- specific effects on the taxonomic composition of the resident microbiota; different strains not only varied in their growth performance in human microbiomes, in some cases they pushed taxonomic composition of the resident community in different directions. In contrast with phenotypes measured in gut microcosms, metabolic profiles measured across various single-carbon-source environments were not reliable predictors of population growth in human microbiomes. Overall, this controlled design reveals the multi-layered ecological dynamics and strain-specific mechanisms that govern the spread of antibiotic-resistant bacteria in individual human-associated microbiomes.

microbiology↗

bioRxiv2024

Drivers of ecological success for Escherichia coli vary among human gut microbiome samples from different individuals

Gut microbial community composition varies from one person to another. Potentially, this means the ecological interactions experienced by individual strains or species also vary among microbiomes of different people. However, testing this directly in human microbiomes and identifying ecological drivers involved is challenging. Here, we use replicated anaerobic microcosms to quantify variability of population growth for a key commensal species among microbiome samples from different individuals, and to identify underlying intra- and interspecific interactions. In a reciprocal transplant experiment, both absolute and relative growth performance of different Escherichia coli strains varied among gut microbiome samples from healthy individuals. This was partly explained by intraspecific competition: ecological success of individual E. coli strains was associated with displacement of resident conspecifics. However, the determinants of E. coli growth varied among samples. In one microbiome sample with a distinctive taxonomic composition, culture acidification by resident microbes impaired growth of all E. coli strains. We identified a strain of Clostridium butyricum contributing to this effect, and showed that transferring it into other microbiomes predictably altered pH, fermentation product profiles (butyrate accumulation and acetate/lactate depletion) and population growth of other species including E. coli, thereby reshaping overall taxonomic composition. Our results suggest natural inter-individual gut microbiome variation translates to variable ecological interactions with incoming bacteria, but these dynamics can be manipulated by a generalizable interspecies interaction. Significance statementGut-microbiome variation among healthy individuals is widely documented, yet its impact on the success of incoming bacterial strains and its implications for microbiome-targeted interventions remain unclear. Here, we test this experimentally by cultivating stool samples from healthy individuals and transplanting strains across samples. We reveal a functional relationship between microbiome variation and growth performance of individual strains. This underscores the challenge of predicting colonization outcomes. Yet, we identify a taxon contributing to the distinct functional profile of one of the samples, and show that its transplantion into other microbiome samples reproducibly alters key properties, including pH and population growth of other bacteria, revealing a common ecological control point. These findings advance our ability to explain and manipulate human gut-microbiome variation.

microbiology↗

bioRxiv2023

Clinical Antibiotic-Resistance Plasmids Have Small Effects on Biofilm Formation and Population Growth in Escherichia coli in vitro

Antimicrobial resistance (AR) mechanisms encoded on plasmids can affect other phenotypic traits in bacteria, including biofilm formation. These effects may be important contributors to the spread of AR and the evolutionary success of plasmids, but it is not yet clear how common such effects are for clinical plasmids/bacteria, and how they vary among different plasmids and host strains. Here, we used a combinatorial approach to test the effects of clinical AR plasmids on biofilm formation and population growth in clinical and laboratory Escherichia coli strains. In most of the 25 plasmid-bacterium combinations tested, we observed no significant change in biofilm formation upon plasmid introduction, contrary to the notion that plasmids frequently alter biofilm formation. In a few cases we detected altered biofilm formation, and these effects were specific to particular plasmid-bacterium combinations. By contrast, we found a relatively strong effect of a chromosomal streptomycin-resistance mutation (in rpsL) on biofilm formation. Further supporting weak and host-strain-dependent effects of clinical plasmids on bacterial phenotypes in the combinations we tested, we found growth costs associated with plasmid carriage (measured in the absence of antibiotics) were moderate and varied among bacterial strains. These findings suggest some key clinical resistance plasmids cause only mild phenotypic disruption to their host bacteria, which may contribute to the persistence of plasmids in the absence of antibiotics.

microbiology↗

bioRxiv2022

Within-patient evolution of plasmid-mediated antimicrobial resistance

Antibiotic resistance (AMR) in bacteria is a major threat to public health, and one of the key elements in the spread and evolution of AMR in clinical pathogens is the transfer of conjugative plasmids. The drivers of AMR evolution have been extensively studied in vitro, but the evolution of plasmid-mediated AMR in vivo remains poorly explored. Here, we tracked the evolution of the clinically-relevant plasmid pOXA-48, which confers resistance to the last-resort antibiotics carbapenems, in a large collection of enterobacterial clones isolated from the gut of hospitalised patients. Combining genomic and experimental approaches, we first characterized plasmid diversity and the genotypic and phenotypic effects of multiple plasmid mutations on a common genetic background. Second, using cutting-edge genomic editing in wild-type multidrug resistant enterobacteria, we dissected three cases of within-patient plasmid-mediated AMR evolution. Our results revealed, for the first time, compensatory evolution of plasmid-associated fitness cost, as well as the evolution of enhanced plasmid-mediated AMR, in bacteria evolving within the gut of hospitalised patients. Crucially, we observed that the evolution of plasmid-mediated AMR in vivo involves a pivotal trade-off between resistance levels and bacterial fitness. This study highlights the need to develop new evolution-informed approaches to tackle plasmid-mediated AMR dissemination.

evolutionary biology↗

bioRxiv2020

The distribution of plasmid fitness effects explains plasmid persistence in bacterial communities

Introductory paragraphPlasmid persistence in bacterial populations is strongly influenced by the fitness effects associated with plasmid carriage. However, plasmid fitness effects in wild-type bacterial hosts remain largely unexplored. In this study, we determined the distribution of fitness effects (DFE) for the major antibiotic resistance plasmid pOXA-48 in wild-type, ecologically compatible enterobacterial isolates from the human gut microbiota. Our results show that although pOXA-48 produced an overall reduction in bacterial fitness, the DFE was dominated by quasi-neutral effects, and beneficial effects were observed in several isolates. Incorporating these data into a simple population dynamics model revealed a new set of conditions for plasmid stability in bacterial communities, with plasmid persistence increasing with bacterial diversity and becoming less dependent on conjugation. Moreover, genomic results showed a link between plasmid fitness effects and bacterial phylogeny, helping to explain pOXA-48 epidemiology. Our results provide a simple and general explanation for plasmid persistence in natural bacterial communities.

microbiology↗

bioRxiv2020

Collateral Sensitivity Associated with Antibiotic Resistance Plasmids

Collateral sensitivity (CS) is a promising alternative approach to counteract the rising problem of antibiotic resistance (ABR). CS occurs when the acquisition of resistance to one antibiotic produces increased susceptibility to a second antibiotic. For CS to be widely applicable in clinical practice, it would need to be effective against the different resistance mechanisms available to bacteria. Recent studies have focused on CS strategies designed against ABR mediated by chromosomal mutations. However, one of the main drivers of ABR in clinically relevant bacteria is the horizontal transfer of ABR genes mediated by plasmids. Here, we report the first analysis of CS associated with the acquisition of complete ABR plasmids, including the clinically important carbapenem-resistance conjugative plasmid pOXA-48. In addition, we describe the conservation of CS in clinical E. coli isolates and its application to the selective elimination of plasmid-carrying bacteria. Our results provide new insights that establish the basis for developing CS-informed treatment strategies to combat plasmid-mediated ABR.

microbiology↗

bioRxiv2020

Dissemination routes of the carbapenem resistance plasmid pOXA-48 in a hospital setting

Introductory paragraphInfections caused by carbapenemase-producing enterobacteria (CPE) are a major concern in clinical settings worldwide. Two fundamentally different processes shape the epidemiology of CPE in hospitals: the dissemination of CPE clones from patient to patient (between-patient transfer), and the transfer of carbapenemase-encoding plasmids between enterobacteria in the gut microbiota of individual patients (within-patient transfer). The relative contribution of each process to the overall dissemination of carbapenem resistance in hospitals remains poorly understood. Here, we used mechanistic models combining epidemiological data from more than 9,000 patients with whole genome sequence information from 250 enterobacteria clones to characterise the dissemination routes of the carbapenemase-encoding plasmid pOXA-48 in a hospital setting over a two-year period. Our results revealed frequent between-patient transmission of high-risk pOXA-48-carrying clones, mostly of Klebsiella pneumoniae and sporadically Escherichia coli. The results also identified pOXA-48 dissemination hotspots within the hospital, such as specific wards and individual rooms within wards. Using high-resolution plasmid sequence analysis, we uncovered the pervasive within-patient transfer of pOXA-48, suggesting that horizontal plasmid transfer occurs in the gut of virtually every colonised patient. The complex and multifaceted epidemiological scenario exposed by this study provides new insights for the development of intervention strategies to control the in-hospital spread of CPE.

microbiology↗

bioRxiv2018

Carbapenemases on the move: it’s good to be on ICE

The evolution and spread of antibiotic resistance is often mediated by mobile geneticelements. Integrative and conjugative elements (ICEs) are the most abundant conjugativeelements among prokaryotes. However, the contribution of ICEs to horizontal gene transferof antibiotic resistance has been largely unexplored. Here we report that ICEs belonging tomating-pair formation (MPF) classes G and T are highly prevalent among the opportunisticpathogen Pseudomonas aeruginosa, contributing to the spread of carbapenemase-encodinggenes (CEGs). Most CEGs of the MPFG class were encoded within class I integrons, which co-harbour genes conferring resistance to other antibiotics. The majority of the integrons werelocated within Tn3-like and composite transposons. A conserved attachment site could bepredicted for the MPFGclass ICEs. MPFTclass ICEs carried the CEGs within compositetransposons which were not associated with integrons. The data presented here provides aglobal snapshot of the different CEG-harbouring ICEs and sheds light on the underappreciatedcontribution of these elements for the evolution and dissemination of antibiotic resistanceon P. aeruginosa.

microbiology↗